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MTECH POWER ELECTRONICS

1

M.TECH

Laboratory Manual

Department of Electrical and Electronics Engineering

Gokaraju Rangaraju Institute of Engineering & Technology

BACHUPALLY, MIYAPUR, HYDERABAD-500090

Gokaraju Rangaraju


2

Institute Of Engineering and Technology

(Approved by A.I.C.T.E and Affiliated to JNTU)

Bachupally, Kukatpally

HYDERABAD 500090.

Power Electronics Lab Record

CERTIFICATE

This is to certify that it is a Bonafide Record of practical work done in the

Power Electronics Laboratory in I sem of I Year during the year……………

Name: ……………………………………………………..

Roll no: …………………………………………………....

Course: M. Tech. ………. Year…… Semester…………

Branch: …………………………………………………...

SIGNATURE OF STAFF MEMBER


3

CONTENTS

LIST OF EXPERIMENTS

SIMULATION CIRCUITS

1. STEP RAMP IMPULSE SINUSOIDAL RESPONSE OF SERIES RLC CIRCUIT

2. 1-PHASE HALF WAVE AND FULLWAVE RECTIFIER WITH R, RL LOAD

3. 3-PHASE BRIDGE RECTIFIER WITH SOURCE INDUCTANCE

4. 1-PHASE FULL WAVE RECTIFIER WITH LOAD FILTER

5. 1-PHASE HALF AND FULLY CONTROLLED RECTIFIER WITH R LOAD

6. 1-PHASE HALF AND FULL WAVE AC VOLTAGE CONTROLLER WITH R LOAD

7. STATE SPACE TO TRANSFER FUNCTION

8. TRANSFER FUNCTION TO STATESPACE

9. SIMULATE BUCK AND BOOST CONVERTER WITH OPEN LOOP OPERATION

10. SIMULATE CUK AND FM BACK CONVERTER WITH OPEN LOOP OPERATION

11. SIMULATE Z-SOURCE INVERTER

12. SIMULATE 3 LEVEL AND 5 LEVEL MULTILEVEL INVERTER

13. SIMULATE STATIC VOLTAGE COMPENSATOR

14.LOW PASS AND HIGH PASS FILTER

15.DIGITAL FILTER


4

PROGRAM OBJECTIVES & OUTCOMES

PROGRAM OBJECTIVES:

1. To simulate and design various gate firing circuits.

2. To familiarize the students by introducing softwares like P- sim, Multisim,

and help them to simulate and analyze different converters.

3. To enable the students to study & simulate circuits using Matlab software

and on hardware kits.

PROGRAM OUTCOMES:

1. Ability to design and conduct simulation and experiments.

2. Ability to use the techniques, skills and modern engineering tools necessary

for engineering practice.

3. Ability to identify, formulate & solve engineering problems with simulation.

4. Ability to simulate characteristics of SCR, MOSFET, IGBT.

5. Ability to simulate gate firing circuits

6. Ability to simulate Rectifiers, Choppers, AC voltage controller, Inverter

circuits and on hardware kits.

7. Ability to simulate Cyclo-converter circuit & calculate harmonics.


5

INDEX

SI.NO: DATE EXPERIMENT SIGNATURE


6

SI.NO: DATE EXPERIMENT SIGNATURE


7

EXPERIMENT 1

STEP RAMP IMPULSE SINUSOIDAL RESPONSE OF

SERIES RLC CIRCUIT

AIM: To study the simulation of step ramp and impulse response of

series RLC circuit using matlab - simulink.

APPARATUS:

1. : 1. MATLAB Software

CIRCUIT DIAGRAM:

STEP RESPONSE OF SERIES RLC CIRCUIT


8

RAMP RESPONSE OF SERIES RLC CIRCUIT

SINUSOIDAL RESPONSE OF SERIES RLC CIRCUIT

THEORY:

The Knowledge of input signal is required to predict the response

of a system.In most of the systems the input signals are not known ahead

of time and it is also difficult to express the input signals

mathemmatically.


9

The step signal is a signal whose values changes from zero to A at

t=0 and remains constant A for t>0. The step signal resembles an actual

steady input to a system.

The mathematical expression of the step signal is,

=0;

The ramp signal is a signal whose value increases linearly with time

from an initial value of zero at t=0.The ramp signal resembles a constant

velocity input to the system.

The mathematical expression of the ramp signal is,

A signal of very large amplitude which is available for very short

duration is called impulse signal.

The impulse signal is denoted by

PROCEDURE:

1. Connect the circuit as per the circuit diagram.

2.Enter the command window of the MATLAB

3.Create a new M-File by selecting file new M-File.

4. Develop MATLAB diagram.

5.Type and save the program in the editor window.

6.Execute the program by either pressing Tools-Run.


10

7.View the results in scope.

MODEL WAVEFORMS (RAMP RESPONSE) :


11

MODEL WAVEFORMS (SINUSOIDAL RESPONSE) :


12

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT

VOLTAGE

OUTPUT

CURRENT


13

GRAPH SHEET


14

GRAPH SHEET

RESULT:


15

EXPERIMENT 2

1-PHASE HALF WAVE AND FULLWAVE

RECTIFIER WITH R, RL LOAD

AIM: To study the simulation of half and full wave rectifier with R &

RL-load using matlab - simulink.

APPARATUS: 1. MATLAB Software CIRCUIT DIAGRAM:

Half Wave Rectifier With R-Load


16

Half Wave Rectifier With RL-Load

Full Wave Rectifier With R-Load


17

Full Wave Rectifier With RL-Load

THEORY:

A single phase half wave uncontrolled converter only has one diode is

employed in the circuit. The performance of the uncontrolled rectifier very much

depends upon the type and parameters of the output (load) circuit.

The simulation circuit of the half wave converter is shown in fig during the

positive half-cycle of input voltage, the diode anode voltage is positive with

respect to cathode and the diode is said to be forward biased.

A single phase full wave diode converter shown in fig with

resistive load. During positive half cycle diodes D1 and D2 are forward

biasedwith repect to cathode.. During negative half cycle of input voltage,diodes

D3 and D4 are forward biased with respect to anode.

PROCEDURE:






18




CALCULATIONS:

The average output voltage for half wave Rectifier with R load,

The average output volage for halfwave rectifier with RL load,

The average output voltage for fullwave rectifier with R load,

The average output voltage for full wave rectifier with RL load,


19

MODEL WAVEFORMS (HALFWAVE RECTIFIER WITH R

LOAD)

:


20

HALFWAVE RECTIFIER WITH RL LOAD :


21

FULLWAVE RECTIFIER WITH R LOAD :


22

FULLWAVE RECTIFIER WITH RL LOAD :


23

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUTCURRENT


24

GRAPH SHEET


25

GRAPH SHEET


26

GRAPH SHEET


27

GRAPH SHEET

RESULT:


28

EXPERIMENT 3

3-PHASE BRIDGE RECTIFIER WITH SOURCE

INDUCTANCE

AIM: To study the simulation of 3 phase bridge rectifier with Source

inductance using matlab - simulink.


Three phase bridge Rectifier With Source Inductance

THEORY:

The source inductance causes outgoing and incomming SCR’s to conduct

together. During the commutation period,the ouput voltage is equal to the average

value of the conducting phase voltages. For a single phase converter,the load

volatge will be zero and for three phase converter,the load voltage is average value


29

of conducting phases. The angular period ,during which both the incomming and

outgoing SCR’s are conducting is known as a commutation angle.

PROCEDURE:








CALCULATIONS:

The average output voltage of converter across the inductance is,


30

MODEL WAVEFORMS:


31

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


32

GRAPH SHEET:

RESULT:


33

EXPERIMENT-4

SINGLE PHASE FULL WAVE RECTIFIER WITH LOAD

FILTER

AIM: To study the simulation of single phase full wave rectifier with

load filter using matlab - simulink.


Single phase full wave Rectifier With Load Filter


34

THEORY:

A rectifier is an electrical device that converts alternating current (AC)

to direct current (DC), which flows in only one direction.A full-wave

rectifier converts the whole of the input waveform to one of constant

polarity (positive or negative) at its output. Full-wave rectification

converts both polarities of the input waveform to pulsating DC (direct

current), and yields a higher average output voltage.

The above circuit diagram is a full wave rectifier with a load

filter.Assume that the value of Ce is very large so that its voltage is

ripple free with an average value of Vo..L is the total inductance the

sorce or line inductance and is generally placed at the input side to act as

an inductance instead of DC choke.

PROCEDURE:








CALCULATIONS:

Output voltage is given by

Vo=VmSinα


35

MODEL WAVEFORMS:


36

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


37

GRAPH SHEET:

RESULT:


38

EXPERIMENT-5

1-PHASE HALF AND FULLY CONTROLLED RECTIFIER

WITH R &RL LOAD

AIM: To study the simulation of half and full wave controlled rectifier

with R & RL-load using matlab - simulink.

APPARATUS: 1. MATLAB Software

CIRCUIT DIAGRAM:

Half Wave Rectifier With R-Load


39

Half Wave Rectifier With RL-Load

Full wave rectifier with R-load


40

Discrete,

Ts = 5e-005 s.

il

i+ -

Vl

v+-

T 4

gm

ak

T 3

gm

ak

T2

gm

ak

T1g

m

ak

Scope

Pulse

Generator 3

Pulse

Generator 2

Pulse

Generator 1

Pulse

Generator

AC R_load

Full wave rectifier with RL-load

THEORY:

A single phase half wave controlled converter only has one SCR is

employed in the circuit. The performance of the controlled rectifier very much

depends upon the type and parameters of the output (load) circuit.

The simulation circuit of the half wave converter is shown in fig (1) during the

positive half-cycle of input voltage, the thyristor anode voltage is positive with

respect to cathode and the thyristor is said to be forward biased. When thyristor T1

is fired at wt=α, thyristor T1 is conducts and input voltage appears the load. When

the input voltage starts to be negative at wt=∏, the thyristor anode is negative with

respect to cathode and thyristor is said to be reverse biased; and it is turned off.


41

The time after the input voltage starts to go positive until the thyristor is fired is

called the delay or firing angle α.

The simulation waveforms of input voltage, output voltage and load current are

shown in fig. This converter is not used in industrial applications because its output

has high ripple content and low ripple frequency.

Gating Sequence. The gating sequence for the thyristor is as follows:

1. Generate a pulse-signal at positive zero crossing of the supply voltage Vs.

2. Delay the pulse by desired angle α and apply it between the gate and cathode

terminal terminals of T1 through a gate-isolating circuit.

Note: Both the output voltage and input current non-sinusoidal. The performance

of the controlled rectifier can be measured by the distortion factor (DF), total

harmonic distortion (THD), PF, transformer utilization factor (TUF), and harmonic

factor.

A single phase full wave converter shown in fig (1) with

inductive load so that load current is continuous and ripple free. During positive

half cycle thyristors T1 and T2 are forward biased, when gating singles are given

to gates of T1 and T2, thyristors are turn–on. Due to the inductive load thyristors

continue to conduct beyond t=∏, even the input voltage is already negative.

During negative half cycle of input voltage, thyristors T3 and T4 are forward

biased, when gate pulses applied to gates of this thyristors they are turned-on

.thyristors T3 and T4 applies a reverse voltage across T1 and T2 as reverse

blocking voltage. T1 and T2 are turned off due to line or natural commutation.

During the period α to ∏, the input voltage Vs and input current

is are positive; and the power flows from supply to load the converter operated in

rectification mode. During period ∏ to ∏+α, the input voltage negative and input

current is positive; and reverse power flow from the load to the source .the

converter is said to be operated in inversion mode

This converter extensively used in industrial applications up to 15 kW.


42

PROCEDURE:








CALCULATIONS:

The average output voltage of full wave rectifier with R load is,

The average output voltage of full wave rectifier with RL load is,


43

MODEL WAVE FORMS: R- LOAD

MODEL WAVEFORMS(RL LOAD):


44

MODELWAVEFORMS(R LOAD):

MODEL WAVEFORMS(RL LOAD):


45

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


46

GRAPH SHEET:


47

GRAPH SHEET:


48

GRAPH SHEET:


49

GRAPH SHEET

RESULT:


50

EXPERIMENT – 6

1-PHASE AC VOLTAGE CONTROLLER WITH

R AND RL - LOAD

AIM: To study the performance of a single phase AC Voltage controller with

RL-load. APPARATUS: 1.Matlab Software CIRCUIT DIAGRAM:

Single Phase AC Voltage Controller Using R Load


51

Single Phase AC Voltage Controller Using RL Load

THEORY:

The AC regulators are used to obtain a variable AC output voltage from a

fixed AC source. A single phase AC regulator is shown in the figure. It consists of

two SCRs connected in anti-parallel. Instead of two SCRs connected in anti

parallel, a TRIAC may also be used. The operation of the circuit is explained with

reference to RL load. During positive half-cycle SCR-1 is triggered into

conduction at a firing angle. The current raises slowly due to the load inductance.

The current continues to flow even after the supply voltage reverses polarity

because of the stored energy in the inductor. As long as SCR-1conducts,

conduction drop across it will reverse bias SCR-2.Hence SCR-2 will not turn on

even if gating signal is applied. SCR-2 can be triggered into conduction during

negative half cycle after SCR-1 turns off.


52

PROCEDURE:








CALCULATIONS:

The average output voltage for AC voltage controller is given as,

The RMS output voltage for AC voltage controller is given as,

MODEL WAVEFORMS: R-LOAD


53

MODEL WAVEFORMS (RL- LOAD):


54

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


55

GRAPH SHEET:

GRAPH SHEET:


56

RESULT:


57

EXPERIMENT 7

STATE SPACE TO TRANSFER FUNCTION

AIM: To get the Transfer Function for the given system by using Matlab.

A= ; B= ; C=


PROGRAM:

a=[-1 0 1 ; 1 -2 0 ; 0 0 3];

b=[0; 0; 1];

c=[1 1 0];

d=[0];

SYS=SS(a,b,c,d)

tf(SYS)

PROCEDURE:



3.Create a new Script by selecting file new Script-File.




58

6.Execute the program by either pressing Tools-Run

CALCULATIONS:

State Equation:

RESULT:


59

EXPERIMENT 8

TRANSFER FUNCTION TO STATE SPACE

AIM: To get the state model for the given transfer function by using

Matlab.


PROGRAM:

n=[1 3];

d=[1 0 -7 -6]

[A B C D]=tf2ss(n,d)

SYS=SS(tf(n,d))

PROCEDURE:



3.Create a new Script by selecting file new Script-File.



6.Execute the program by either pressing Tools-Run


60

CALCULATIONS:

RESULT:


61

EXPERIMENT 9

SIMULATE BUCK AND BOOST CONVERTER WITH

OPEN LOOP OPERATION

AIM: To study the simulation of buck and boost conveter with open

loop operation using matlab - simulink.


CIRCUIT DIAGRAM:

Simulaion of Buck Converter

Simulation of Boost Converter


62

THEORY:

DC converters can be used as switching mode regulators to convert a dc

voltage normally unregulated to a regulated dc output voltage. Regulation is

normally achieved by PWM at fixed frequency and switching deive is normally

BJT,MOSFET and IGBT .Switching regualtors are comercially available as

integrated circuits.

Buck and Boost converters are the types of switching mode regulators.

In Buck regulator the average output voltage Va is lessthan the input

voltageVs.It acts as step down converter.Ciruit operation is divided into two

modes. First mode begins when transistor is switched ON at t=0, the input current

which rises flows through filterinductor L ,filter capacitor C and load resistor R.

Second begins when transistor is switched OFF at t=t1.The freewheeling diode Dm

conducts due to energy stored in inductor and inductor current continues to flow

through L,C and load and diode Dm.

In Boost regulator the output voltage is greater than the input voltage.It acts

as a stepup Converter.Circuit operation is divided into two modes.First mode

begins when transistor is switched ON at t=0, the input current which rises flows

through inductor L and transistor. Second begins when transistor is switched OFF

at t=t1. The current that flowing through transistor would now flow through L, C

,Load and diode Dm.

PROCEDURE:






63



7.View the results in scope

CALCULATIONS:

The average output voltage for boost converter is,

The average output voltage for buck converter is,

MODEL WAVFORMS:

Boost converter:


64

Buck converter:

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


65

GRAPH SHEET:


66

GRAPH SHEET:


67

RESULT:


68

EXPERIMENT 10

SIMULATE CUK AND FM BACK CONVERTER

WITH OPEN AND CLOSED LOOP OPERATION

AIM: To study the simulation of cuk and FM back conveter using matlab

- simulink.


CIRCUIT DIAGRAM:

Simulation of cuk converter


69

Simulation of Flyback Converter

THEORY:

DC converters can be used as switching mode regulators to convert a dc

voltage normally unregulated to a regulated dc output voltage. Regulation is

normally achieved by PWM at fixed frequency and switching deive is normally

BJT,MOSFET and IGBT .Switching regualtors are comercially available as

integrated circuits.

Cuk converter is similar to buck-boost converter.Cuk converter provides an

output voltage less than or greater than the input voltage. Where the output voltage


70

polarity is opposite to that of input voltage.when input voltage is turned on and

transistor is switched off.Diode Dm is forward biased and capacitor C charged

through inductor L,Dm and the input voltage supply.

PROCEDURE:








CALCULATIONS:

The average output voltage for CUK converter is,

The average output voltage for flyaback converter is,


71

MODEL WAVEFORMS(Cuk converter):

Flyback converter:


72

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


73

GRAPH SHEET:


74

GRAPH SHEET:

RESULT:


75

EXPERIMENT 11

SIMULATE Z-SOURCE INVERTER

AIM: To study the simulation of Z source inverter using matlab -

simulink.


CIRCUIT DIAGRAM:

THEORY:

A Z-source inverter is a type of power inverter , a circuit that converts direct

current to alternating current. It functions as a buck boost inverter without making


76

use of DC-DC converter bridge due to its unique circuit topology.

Z source networks provides an efficient means of power conversion between

source and load in a wide range of electric power conversion applications.

The source can be either a voltage source or a current source.The DC source of a

ZSI can either be abttery ,a diode rectifier or a thyristor converter.The load of a

ZSC can either be inductive or capacitive or another Z source network.

PROCEDURE:








CALCULATIONS:


77

MODEL WAVFORM:


78

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


79

GRAPH SHEET:

RESULT:


80

EXPERIMENT 12

SIMULATE 3 LEVEL AND 5 LEVEL MULTILEVEL

INVERTER

AIM: To study the simulation of 3 level and 5 level multilevel inverter

using matlab - simulink.


CIRCUIT DIAGRAM:

Simulation Of Three Level Inverter


81

Simulation of Five Level Inverter


82

THEORY:

An inverter converts fixed DC voltage to an AC voltage of variable

frequency and of fixed or variable magintude.A practical inverter has eitheer a

battery,a solar powered dc voltage or a line frequency derived DC voltage source.

Inverters are widely used from very low power portable electronic systems such as

the flashlight discharge system in a phtography camera to a very high power

industrial sysytems.

Inverters are designed using semiconductor devices such as power

transistors ,MOSFET’S,IGBT’S GTOS And thyristors.

PROCEDURE:








CALCULATIONS:


83

MODEL WAVFORMS (3 LEVEL INVERTER):

5 LEVEL INVERTER:


84

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


85

GRAPH SHEET:


86

GRAPH SHEET:

RESULT:


87

EXPERIMENT 13

SIMULATE STATIC VOLTAGE COMPENSATOR

AIM: To study the simulation of static voltage compensator using matlab

- simulink.


CIRCUIT DIAGRAM:

Simulation of Static voltage Compensator


88

Simulation of trigerring signal genearator of SVC

Simulation of SVC(FC-TCR)


89

THEORY:

A static Var compensator is a set of electrical devices providing fast acting

reactive power on high voltage electricity transmission networks. SVC is an

automated impedence matching device,design to bring the system close to unity

power factor. SVC used in two min situations:

Connected to power system to regulate

transmission voltage .

Connected near large industrial loads

to improve power quality.

In transmission applications,SVC is used to regulate the grid voltage.If the

power system reactive load is capacititve ,SVC’s will use thyristor controlled

reactors to consume VAR’s from the system lowering the system voltage.Under

inductive conditions,capacitor banks are automatically switched in thus

providing higher sytem volatges.

PROCEDURE:









90

MODEL WAVFORMS:


91

TABULAR COLUMN:

SL.NO

INPUTVOLTAGE

OUTPUT VOLTAGE

OUTPUT CURRENT


92

GRAPH SHEET:

RESULT:


93

EXPERIMENT-14

LOW PASS AND HIGH PASS FILTER

AIM: To study the simulation of Low pass and High pass Filter using

matlab - simulink.


CIRCUIT DIAGRAM:

LOW PASS FILTER

HIGH PASS FILTER


94

THEORY:

A low-passfilter isa filter that passes signals with a frequency lower than

a certain cutoff frequency and attenuates signals with frequencies higher

than the cutoff frequency. The amount of attenuation for each frequency

depends on the filter design.

A High Pass Filter or HPF, is the exact opposite to that of the previously

seen LowPass filter circuit, as now the two components have been

interchanged with the output signal ( Vout ) being taken from across the

resistor as shown.

PROCEDURE:








CALCULATION:

Output voltage of low pass filter

Output voltage of high pass filter


95

MODEL WAVEFORM:

LOW PASS FILTER

HIGH PASS FILTER


96

GRAPH SHEET


97

GRAPH SHEET

RESULT:


98

EXPERIMENT-15

DIGITAL FILTER

AIM: To study the simulation of Digital Filter using matlab - simulink.


CIRCUIT DIAGRAM:


99

THEORY:

In signal processing, a digital filter is a system that performs

mathematical operations on a sampled, discrete-time signal to reduce or

enhance certain aspects of that signal. This is in contrast to the other

major type of electronic filter, the analog filter, which is anelectroni

circuit operating on continuous-time analog signals

A digital filter system usually consists of an analog-to-digital

converter to sample the input signal, followed by a microprocessor and

some peripheral components such as memory to store data and filter

coefficients etc. Finally a digital-to-analog converter to complete the

output stage.

Infinite impulse response (IIR) is a property applying to many linear

time-invariant systems. Common examples of linear time-invariant

systems are most electronic and digital filters. Systems with this

property are known as IIR systems or IIR filters, and are distinguished by

having an impulse response which does not become exactly zero past a

certain point, but continues indefinitely. This is in contrast to a finite

impulse response in which the impulse response h(t) does become

exactly zero at times t > T for some finite T, thus being of finite duration.

PROCEDURE:









100

CALCULATION:

MODEL WAVEFORM:


101

GRAPH SHEET

RESULT:


102

POWER CONVERTERS LAB

SEM II


103

Contents PageNo

1.Thyristorised Drive for PMDC Motor with Speed Measurement and

Closed Loop Control.

2.IGBT based Single 4 Quadrant Drive for PMDC Motor with Speed

Measurement & Closed Loop Control.

3.Closed Loop Control of DC Motor Using Three Phase Fed Four

Quadrant Chopper Drive

4.Three Phase Input Thyristorised Drive for DC Motor with Closed

Loop Control.

5. Single Phase Cycloconverter

6. Speed Control of 3 Phase Wound Rotor Induction Motor.

7. Single Phase Fully Controlled Bridge Converter.

8. Single Phase Half Controlled Bridge Converter

9. v/f drive for AC 3-Ø Squirrel-cage induction motor.

10. closed loop speed control of dc motor using pi, pd and pid controllers

11.Closed loop speed control of AC motor- DC generator set with load using

PI,PID controllers

12.Indirect speed control of AC motor using armature V/F control with PI,PID controllers


104

EXPERIMENT 1

THYRISTORISED DRIVE FOR PMDC MOTOR WITH

SPEED MEASUREMENTAND CLOSED LOOP

CONTROL INTRODUCTION:

Closed loop dc motor speed control unit presented here is based on popular 8085

microprocessor chip. Using this instrument we can set RPM of the motor from 10

rpm to 1590 rpm in steps of 10 rpm.The motor will come to its set rpm within few

seconds irrespective in the variation of supply voltage and load.

SPECIFICATIONS:

1. Thyristors (marked as A,C&G) :2 nos(25TTS12)

SI.No Parameters Ratings

1 VRRM 1200V

2 VDRM 1200v

3 ITRMS 25 Amps

4 ITAV(180 conduction) 16 Amps

2. Diodes (marked as A & C) :3 no


1 VRRM 1200v

2 ITRMS 16 Amps

3 ITAV 16 Amps

3. Fuses: 2A replaceable fuses are provided on MF-20 sockets at the back side

of the instrument


105

4. Firing circuit

CIRCUIT OPERATION:

This unit is based on 8085 microprocessor chip. This unit generates two line

synchronized triggering pulses.RPM can be set through key board of the unit.

Firing pulses generated are based on 8253 programmable interval timer.8253 is

assigned to work in mode 5.Counter 2 of 8253 are used to generate firing pulses.

The unit is programmed to adjust its firing angle. The effect can be seen by

connecting CRO across the terminals of the motor.

The tachogenerator attached to the shaft of the motor converts rpm to DC

voltage. This voltage is sensed by microprocessor. The system generates firing

pulses to keep rpm of the motor constant. The circuit diagrams and programs are

provided with this manual. The analog voltage corresponding to rpm is converted

digital voltage by ADC 0809.Then the system compares the running RPM with the

set RPM by look up table. If the running speed less than the set speed then the

firing angle is decreased by one degree & if the running speed is more than the set

speed then the firing angle is increased by one degree. The system is keep on

comparing the set speed and running speed.

8253 configuration:

System is working with the clock frequency of 6.144 MHz This frequency is

internally divided by two in 8085 microprocessor chip. Therefore 3.072 MHz clock

is generated. This frequency is again divided by two internally. Therefore 1.536

MHz clock is generated.

SI.No Parameters Particulars

1 Input power

supply

230V from the mains for

synchronization and power supply

2 Output: Two isolated gate signals for

thyristors

3 Gate drive

current:

200Ma

4 Firing angle Variable


106

Therefore clock time period =1/T

= 1/1.536*10e-6

=0.651 us

No. of clocks for 10ms=10 ms/0.651 us=15,360

In order to generate delay of 1 degree

Required counts=15,360/180=85

85 is in decimal number when we converted in to hexadecimal the number is

55H.Therefore the number 55H must be loaded in 8253 register in order to get a

delay of 1 degree.

Therefore if the running speed is less than the set speed then 55H is

subtracted from the content of 8253 counter 1 consequently firing angle is

decreased by one degree & if the running speed more than the set speed then 55H

is added to the content of 8253 counter 1 consequently the firing angle is increased

by one degree. The system is keep on comparing the set speed and running speed.

Memory map of 8253 is as follows

I/O Device Address

Timer 0 C8

Timer 1 C9

Timer 2 CA

Control port CB

Timer 2 used for this experiment.

8255A configuration

8255A is used to read the content of ADC 0809.ADC 0809 read the output

of tachogenerator and convert it into the digital voltage. Digital signals are input to

PORT A of 8255.ADC starts conversion by sensing output signal from 8255A to

SOC line through PC3.Analog signal is input to 0809 by channel 1 by selecting

channel 1 through PC2,PC1,PC0 (000).End of conversion is sensed by PC7.

PORT A is input PORT


107

PORT B is not used

PORT C LOWER is output PORT

PORT C UPPER is input PORT

Memory map of 8255A is as follows.

I/O PORT Address

PORT A F0

PORT B F1

PORT C F2

Control registers F3

For more details refer program & circuit diagram.

A wide range of memory is from 8000H to FF9FH is provided for the user to write

and execute their own programs.

HOW TO CONDUCT THE EXPERIMENT:

AIM: To control the speed of the PMDC motor using thyristorised converter unit.

APPARATUS: Thyrisroised converter unit, CRO, patch cards, etc

THEORY: Rectifier converts AC supply to DC supply. with thyristor, variable

DC supply 0 V to maximum can be obtained from a fixed AC source by triggering

(turning ON) SCR i.e., by applying gate current to the SCR at any desired instant

when the SCR is applied with positive voltage to anode. Unlike diode, SCR can

block the forward voltage when gate current is not supplied. Hence converters

using SCR’s are termed as controlled rectifier. Normally for DC power

requirement such as in DC drives single phase full wave controlled rectifier are

used.

SINGLE PHASE HALF CONTROLLED BRIDGE WITH MOTOR LOADS.

When the single phase semi-converter is connected with R-L/motor load a

freewheeling diode must be connected across the load. During positive half cycle

T1 is forward biased & T1 is fired at ωt=α, the load is connected to the input

supply through T1 and D1 during period α≤ω≤π, During the period from π≤ωt≤


108

(π+α), the input voltage in negative and free wheeling diode Df is forward biased,

Df conducts to provide the continuity of current in the inductive load. the load

current is transferred from T1 and D1 to Df, and thyristor T1 and D1 are turned off

at ωt=π.During negative half cycle of input voltage, thyristor T2 is forward biased,

and the firing of T2 at ωt=π+αwill reverse bias Df.The diode Df is turned off and

the load connected to the supply through T2 and D2.

When the load is inductive and T1 is triggered, first it will conduct with D1 to pass

current through load. When the supply voltage is negative load emf will drive

current through T1D2.This is an exponentially decreasing current. When the new

negative half cycle begins T1 is in conduction and it would keep on conducting

with D1 as if triggered at ωt=0.In this case load may not receive the D.C power. To

ensure proper operation, at the beginning of positive half cycle T2 has turned off

and similarly T1 should be turned off when negative half cycle begins. This is

achieved by the free wheeling diode.

For R-L load with freewheeling diode the average output voltage can be found

from

11

Vdc (av) = (1/11) α∫ Vm sinθdθ

= (Vm/π) [-cosθ]απ

Vdc (av) =(Vm/π)[1+cosα]

PROCEDURE:

1. Connect motor terminals to power circuit & speed sensor to feedback

terminals socket

2. Switch on the unit, Display shows –sda 85.

3. Now press GO 4B00 EXEC keys.

4. Display shows SPDC CO indicates that single phase DC motor control.

5. Press NEXT key.

6. Display shows rP indicates select rpm you would like to run motor.

7. Now enter rpm through keyboard

Example for rpm 1000

Press keys 1000

8. Switch on the power circuit.

9. Press exec key


109

Now motor starts rotating it reaches its set rpm within few seconds.

10. To increase RPM press NEXT key. Pressing next key repeatedly increases

rpm by 10 every time however microprocessor will give the command to

power ciruit only when EXEC key is pressed.

11. To decrease RPM press PREV key. Pressing PREV key repeatedly decreases

rpm by 10 every time however microprocessor will give command to power

circuit only when EXEC key is pressed.

12. Note down motor voltage.

13. Now note down the firing angle using CRO.

14. Add the weight upto 250 grams in the interval of 50 grams. Study the

performance of the motor for the closed loop.

TABULAR COLUMN:

RPM=

SI.No Weight in

gram

Load

voltage

Load current Firing angle

1

2

3

RESULT:


110


111


112

EXPERIMENT 2

CLOSED LOOP CONTROL OF DC MOTOR USING

FOUR QUADRANT CHOPPER DRIVE

INTRODUCTION:

Closed loop dc motor speed control using four quadrant chopper drive

presented here is based on popular 8085 microprocessor chip. Using this

instrument we can set RPM of the motor upto 1590rpm in steps of 10rpm. The

motor will come to its set rpm within delay time irrespective in the variation of

supply voltage and load.

CHOPPER:

The chopper is used to convert a dc voltage of fixed amplitude to the DC of

variable pulse width. The output voltage is controlled by controlling the duty cycle

of the chopper. These choppers find applications in variable voltage DC power

supplies, battery chargers, electric traction etc.

SPECIFICATIONS:

CHOPPER POWER CIRCUIT

SI.No. Devises/

parameters

Ratings

1 IGBTs:

IRG30B120KD

VRRM

ITRMS

ITAV

4No.

600V

40 Amps

30Amps

2 Max. allowed

average current

3 A DC

3 Max allowed

dc supply

voltage

30VDc


113

CHOPPER FIRING CIRCUIT BUILT IN

Firing circuit is based on 8085 microprocessor


1 Input power supply: 230V from the

mains for the unit.

Drive is operated in I and II quadrant. In the reverse rotation of the motor chopper

operates in the III and IV quadrant.

During forward rotation of the motor the chopper operates in forward motoring

(E1.)(I quadrant)& forward regenerative braking (II quadrant) mode. During

reverse rotation of the motor the chopper operates in reverse motoring (E3)(III

quadrant) & reverse regenerative braking (IV quadrant ) mode. The direction of the

motor can be changed from forward direction to reverse direction immediately by

pressing key 1 or 3 from the keyboard. However it is recommended to reverse the

motor by reducing the supply voltage and then reset the voltage to avoid large

reverse current at the time of reversing.

8255 CONFIGURATION:

8255A is used to read the content of ADC 0809.ADC 0809 read the output

of speed sensor and converts it into the digital voltage. Digital signals are input to

PORT A of 8255. ADC starts conversion by sensing output signal from 8255A to

SOC line through PC3. Analog signal is input to 0809 by channel1 by selecting

channel 1 through PC2, PC1, and PC0 (000). End of conversion is sensed by PC7.

PORT A is input PORT for Data transfer

PORT B is output PORT to generate triggering pulses.

PORT C LOWER is output PORT to select analog input line Io and to start

conversion.

PORT C UPPER is input PORT

Memory map of 8255A is as follows.

I/O PORT Address

PORT A F0


114

PORT B F1

PORT C F2

Control registers F3

A wide range of memory is from 8000H to FF9FH is provided and user

to write and execute their own programs.

2 Output: Isolated gate signals

4 Duty cycle Variable from minimum to maximum

5 Operating

Frequency:

50HZ approximate

RECOMMENDED FOR THE EXPERIMENTS:

TRIGGERING PULSES GENERATIONS:

This unit is based on 8085 micro processor chip. This unit generates four

chopper triggering pulses CH1, CH2, CH3 &CH4. RPM can be set through

Name of the Equipment Specifications Quantity

1. Input source: DC power supply: 30/20A 1no.

2. Control modules: Chopper circuit 1no.

3. Output(load) PMDC Motor 12v with

tacho feedback

1no.

4. Measuring

Instruments:

Oscilloscope 1 no.

5. Connecting wires: Patch cords for

connecting.


115

keyboard of the unit. Triggering pulses are generated by programming 8085.

Triggering pulses are generated to operate the chopper in all four quadrants.

This unit is programmed to adjust its firing pulse width keeping frequency

constant. the effect can be seen by connecting CRO across the terminals of the

motor.

The non contact speed sensor is attached to the shaft of the motor to converts

rpm to DC voltage. This voltage is sensed by microprocessor using ADC. The

system generates firing pulses to keep rpm of motor constant. The triggering

scheme is presented in the diagrams and programs are provided with this manual.

The analog voltage corresponding to rpm is converted to digital voltage by ADC

0809. The digital signal is read by interfacing 8255 Programmable Peripheral

Interfacing 8255 device. Then the system compares the running RPM with the set

RPM by look up table. if the running speed is less than the set speed then the duty

cycle of the triggering pulses are increased by few micro seconds vice versa. The

system keeps on comparing the set speed and the running speed. In the forward

rotation of the motor chopper.


AIM: To construct chopper drive circuit and to control PMDC motor.

APPARATUS: four quadrant chopper circuit, DC power supply 30V/2A, CRO,

patch cards, etc.

THEORY:

Chopper converts fixed DC voltage to variable DC voltage through the use

of semi conductor devices. The DC to DC converters have gained popularity in the

modern industry. Some practical applications of DC to DC converters includes

armature voltage control of DC voltages converting one DC voltage level to

another level , and controlling DC power for wide verity of industrial processes.

The time ratio controller (TRC) is a form of control for DC to DC conversion.

In four quadrant dc chopper drives, a motor cam be made to work in forward

motoring mode (I quadrant), forward regenerative braking mode (II quadrant)

,reverse motoring mode (III quadrant) and reverse regenerative braking mode(IV

quadrant). The circuit shown offers four quadrant operation of a PMDC motor. its

operation in the four quadrants can be explained as under.

Forward motoring mode (I quadrant): during this mode or first quadrant

operation. Chopper CH2, CH3 are kept off, CH4 is kept on where as CH1 is


116

operated. When CH1, CH4 are ON, motor voltage is positive and positive

armature current rises. When CH1 is turned off, positive armature operation in first

quadrant is obtained.

Forward regenerative breaking mode (II quadrant): A dc motor can work

in the regenerative-breaking mode only if motor generated emf is made to exceed

the dc source voltage. For obtaining this mode CH1, CH3, and CH4 are kept off

whereas CH2 is operated. When CH2 is turned on, negative armature current rises

through CH2, D4, Ea, La, and Ra. When CH2 is turned OFF, diodes D1, D4 are

turned on the motor acting as a generator returning energy to dc source. This

results in forward regenerative-breaking mode in the second-quadrant.

Reverse motoring mode (III quadrant): This operating mode is opposite to

forward motoring mode. Chopper CH1, CH4 are kept off. CH2 is kept on whereas

CH3 is operated. When CH3 and CH2 are on, armature gets connected to source

voltage Vs so that both armature voltage and armature current ia is negative. As

armature current is reversed, motor torque reversed and consequently motoring

mode in third quadrant is obtained. When CH3 is turned off, negative armature

current freewheels through CH2, D4, Ea, La, Ra; armature current decreases and

thus speed control is obtained in third quadrant. Note that during this mode polarity

of Ea is opposite to that shown in fig.

Reverse Regenerative-breaking mode: As in forward braking mode,

reverse regenerative braking mode is feasible only if motor generated emf is made

to exceed the source voltage. For this operating mode, CH1, CH2 and CH3 are

kept off whereas CH4 is operated. When CH4 is turned on, positive armature

current ia rises through CH4, D2, Ra, La, Ea. When CH4 is turned off, diodes D2,

D3 begin to conduct and motor acting as generator returns energy to dc source.

This leads to reverse regenerative-braking operation of the dc separately excited

motor in fourth quadrant.

PROCEDURE:

1. Connect speed sensor to feedback socket.

2. Power circuit connections are made as shown in the circuit diagram.

3. Connect motor terminals respective points in the power circuit, ammeter

and voltmeters as shown in the circuit diagram to observe the respective

current and voltage waveforms.

4. Check the connections and conform the connections made are correct

switching on power supply.

5. Switch on the four quadrant chopper unit, Display shows –sda 85.


117

6. Now press GO 4B00 EXEC keys. (the monitor program for closed loop

control of DC motor using four quadrant chopper is stored from the

memory location 4B00H)

7. Display shows 4Qd CH indicates four quadrant chopper.

8. Press NEXT key.

9. Display shows SEL CH indicates select chopper to start with 1st or 3

rd

quadrant chopper.

10. Press key 1 or 3 (if key 1 is pressed then chopper operates in 1st & 2

nd

quadrant-forward rotation. If key 3 is pressed then chopper operates in 3rd

& 4th

quadrant-reverse rotation).

11. Display shows rP indicates select rpm you would like to run motor.

12. Now enter rpm through keyboard

Example for rpm 1000

Press keys 1, 0, 0, 0.

13. Switch on the power supply keeping supply voltage at minimum then

switch on the power circuit.

14. Press key EXEC from keyboard of the firing unit.

15. Slowly set the DC supply voltage to suitable value (15 V approximately)

Now motor starts rotating slowly it reaches its set rpm within certain

delay time.

16. Note down the motor voltage, motor current.

17. Observe the load voltage & load current waveforms using CRO.

18. Load the motor in steps of 50 grms. Study the performance of the motor

for the closed loop by loading motor up to 250 grms.

19. Reduce the power supply voltage; switch off the power circuit and DC

power supply.

20. Press RESET key to stop firing pulses, chopper unit mains & remove the

connections.

TABULAR COLUMN:

FORWARD ROTATION


118

Set rpm =1000rpm

SL.

NO.

Weight

In KGs

Load

Voltage

Load

Current

Running

speed

In rpm

1.

2.

3.

REVERSE ROTATION:

Set rpm = 1000rpm

SL.

NO.

Weight

In KGs

Load

Voltage

Load

Current

Running

speed

In rpm

1.

2.

3.

Result:


119


120

\


121

EXPERIMENT 3

CLOSED LOOP OF DC MOTOR USING THREE PHASE

FED FOUR QUADRANT CHOPPER DRIVE

INTRODUCTION:

Closed loop dc motor speed control unit presented here is based on PID

controller & four quadrant chopper power circuit. The motor will come to its rpm

within few seconds irrespective in the variation of load. The PID trainer is to study

the characteristics of the feedback control circuit. The speed of the DC motor is

controlled by the PID (proportional integral and derivative) controller method. The

output of the controller then adjusts the value of each variable in the control system

until is it equal to predetermined value called a set point. The system controller

must maintain each variable as close as possible to its point value and it must

compensate as quickly and accurately as possible for any change in the variable

caused by the motor.

The chopper is used to convert a DC voltage of fixed amplitude to the DC of

variable pulse width. The output voltage is controlled by controlling the duty cycle

of the chopper. These choppers find application in variable speed DC motor

controls, DC power supplies, battery chargers, electric traction etc. four quadrant

choppers having applications in reversible motor drive. 3 phase AC is converted

into DC by isolation transformer and diode rectifier. The rectified output is fed to

four quadrant chopper as DC input.

DESCRIPTION OF THE SETUP:

The setup consists of DC motor 0.5HP, 220V, 1500rpm whose speed has to

be controlled in closed loop control using PID controller & IGBT drive. Firing

circuit is based on PID controller & power circuit is based on four quadrant

chopper. Automatically variable DC supply is provided to set the speed of the DC

motor. A speed sensor is attached to the motor shaft. A tachometer constructed

internally is provided to read the motor speed in rpm. A pulley is attached to the

shaft of the DC motor for mechanical loading arrangement. An ammeter is

provided to notice motor current. And a voltmeter is also provided to read voltage

across the DC motor.

SPEED CONTROL AND SPEED MEASUREMENT:


122

A DC voltage from three phase rectifier supply controlled from PID

controller through the IGBT based four quadrant choppers. The DC supply is given

to the chopper. The field supply is separately excited by the single phase bridge

rectifier provided at the power circuit. The speed sensor must be connected from

the motor assembly to the instrument by the socket provided in the front panel of

the control circuit. The speed sensor, sense the speed of the motor and generates

rectangular signal whose frequency is proportional to the rpm. The signal

conditioner converts frequency into voltage corresponding to rpm. The digital

panel meter displays the speed in rpm at the front panel of the instrument.

SPECIFICATIONS:

THREE PHASE BRIDGE RECTIFIER

1. Diode (marked as A&C) :4 no

2.IGBT,s : 4no GP30B120KD-E with diodes


1 VRRM 1200v

2

ITRMS 60 A

3 ITAV 30 A

3. Fuses:

2A replaceable fuses are provided on MF-20 sockets at the back side

of the instrument

SI.NO

Parameters Ratings

1 VRRM 1200v

2 ITRMS 25 A

3 ITAV 16 A


123

4. Field supply:

220V/2A diode bridge rectifier.

SPECIFICATION OF PID CONTROLLER:

1. Power : Mains ON/OFF switch to the unit with build in

indicator

2. SET RPM (knob) : This knob is used to set the rpm

3. SET RPM (display) : This rpm indicator (display) shows the rpm set by

knob

4. RUN RPM (display) : This rpm indicator (display) shows the running

rpm

5. P : The switch makes P ON/OFF

6. I : The switch makes I ON/OFF

7. D : The switch makes I ON/OFF

8. P GAIN : Used to set the gain of the P controller

9. I TIMING : Used to set the integral time I controller

10. D GAIN : Used to set the gain of the D controller

11. FEEDBACK : This socket is used to connect the speed sensor

12. ERROR OUTPUT : Show error output

13. P OUTPUT : Shows output of p controller

14. I OUTPUT : Show output of I controller

15. D OUTPUT : Shows output of D controller

16. PID OUTPUT : Shows output of PID controller

17. GND : Measurements are made with respect to this point

18. Gate & Source (socket): These sockets provides isolated triggering pulses to

IGBTs


124

CIRCUIT OPERATION:

This speed control unit is based on PID controller. This unit generates four

triggering pulses. RPM can be set through knob provided on the unit. The unit is

programmed to adjust its duty cycle. The unit generates four chopper triggering

pulses CH1, CH2, CH3 & CH4. RPM can set through knob of the unit. Triggering

pulses are generated to operate the chopper in all for quadrants. The unit

programmed to adjust its firing pulse width keeping frequency constant.

The feedback sensor (proximity detector) attached to the shaft of the motor is

magnetic sensor. The sensor output goes high whenever metal screw comes near

the switch. The sensor output is connected to the voltage to frequency converts.

The output voltage of the F/V converter is proportional to running rpm. Then the

system compares the running RPM with the set RPM. If running speed is less than

the set speed then the duty cycle is increased& if the running speeds more than the

set speed then the duty is decreased. The system is keeps on comparing the set

speed and running speed. In the forward rotation of the motor chopper drive is

operated in 1 and 2 quadrant. In the reverse rotation of the motor chopper operates

in the 3 and 4 quadrant.

During forward rotation of the motor the chopper operates in forward

motoring (1quadrant) &forward regenerative breaking (2quadrant) mode. During

reverse rotation of the motor the chopper operates in reverse motoring (3quadrant)

&reverse regenerative breaking (4quadrant) mode.

THEORY:

chopper converts fixed DC voltage to variable DC voltage through the use of

semiconductor devices. The DC to DC converters have gained popularity in the

modern industry. Some practical applications of DC to DC converter include

armature voltage control of DC motors converting one DC voltage level to another

level, and controlling DC power for wide variety of industrial processes. The time

ratio controller (TRC) is a form of control for DC to DC conversion.

In four quadrant dc chopper drives, a motor can be made to work in

forward-motoring mode (1quadrant), forward regenerative breaking mode

(2quadrant), reverse motoring mode (3quadrant) and reverse regenerative breaking

mode (4quadranet).the circuit shown offers four quadrant operation of a separately-

excited dc motor. This circuit consists of 3 phase fed diode rectifier, four choppers,


125

four diodes and a separately-excited dc motor. Its operation in the four quadrants

can be explained as under.

Forward motoring mode (1quadrant): during this mode or first-quadrant

operation, chopper CH2, CH3 are kept off, CH4 is kept on whereas CH1 is

operated. When CH1, CH4 are on, motor voltage is positive and positive armature

current rises. When CH1 is turned off, positive armature current free-wheels and

decreases as it flows through CH4, D2.In this manner controlled operation in 1st

quadrant is obtained.

Forward regenerative breaking mode (II quadrant): a dc motor can work in the

regenerative-breaking mode only if motor generated emf is made to exceed the dc

source voltage. For obtaining this mode CH1, CH3 and CH4 are kept off whereas

CH2 is operated. When CH2 is turned on, negative armature current rises through

CH2, D4, Ea, La, Ra. When CH2 is turned off, diodes D1, D4 are turned on and

the motor acting as a generator returning energy to dc source. This results in

forward regenerative-breaking mode in the second-quadrant.

Reverse motoring mode (III quadrant): This operating mode is opposite to forward

motoring mode. Chopper CH1, CH4 are kept off, CH2 is kept on where as CH3 is

operated. When CH3 and CH2 are on, armature gets connected to source voltage

Vs so that both armature and voltage armature current Ia is negative. As armature

current is reverse, motor torque reversed and consequently motoring mode In third

quadrant is obtained. When CH3 is turned off, negative armature current free

wheels through CH2 , D4, Ea, La, Ra, armature current decreases and thus sped

controlling obtained in 3rd

quadrant. Note that during this mode polarity of Ea is

opposite to that shown in figure.

Reverse regenerative –braking mode: As in forward braking mode, reverse

regenerative-braking mode is feasible only if motor generated emf is made to

exceed the source voltage. For this operating mode, CH1, CH2 and CH3 are kept

off where as CH4 operator is operated. When CH4 is turn on, positive armature

current Ia rises through CH4, D2 Ra, La, Ea. When CH4 is turn off, diodes D2, D3

begin to conduct and motor acting as generator return energy to dc source. The

leads to reverse regenerative – braking operation of the DC separately exited motor

in 4Th

quadrant.


126


127

If the gain of p controller is less than the error voltage (difference

between set & running) is more. If the gain is i9ncreased the error voltage is

reduced. The I controller further reduces the error. If the timing of I controller is

increased almost the error is reduced. However has negligible effect on overall

system.

EXPERIMENTAL


Aim: To construct three phase fed closed loop chopper drive circuit and to control

the speed of the separately-excited dc motor.

Apparatus: Chopper power module, chopper firing unit, three phase isolation

transformer, CRO, patch cards, etc.

PROCEDURE:

1. Connect motor terminals (field &armature) to respective points in the power

circuit &speed sensor to feedback terminals socket.

2. Circuit connections are made as shown in the circuit diagram.

3. Connect 3 pin power cord from power unit (rectifier) to the mains supply.

4. Switch on the field supply of the motor.

5. Switch on the three phase power input.

6. Switch on the power circuit through MCB.

7. Keeping PID ON now switch on firing unit.

8. Set the rpm through the knob.

9. Switch ON P, I, D switches adjust the gains.

10. Load the motor

11. Switch off power circuit by MCB, switch off firing circuit, switch off field

supply & remove the connections.

TABULAR COLUMN:

Sl.No Load Current Load Voltage Running

Rmp

1.

2.

3.


128

Note: Field supply must be switched on before applying voltage to armature.

Result:

4.


129


130


131


132


133

EXPERIMENT 4

THREE PHASE INPUT THYRISTORISED DRIVE FOR

DC MOTOR WITH CLOSED LOOP CONTROL

INTRODUCTION:

Closed loop dc motor speed control unit presented here is based on PID

controller & thyristor power circuit. The PID trainer is to study the characteristics

of the feedback control circuit. The speed of the DC motor is controlled by the PID

(proportional, Integral and Derivative) controller method. The output of the

controller then adjusts the value of each variable in the control system until it is

equal to predetermined value called a set point. The system controller must

maintain each variable as close as possible for any change in the variable caused

the motor.

Power circuit consists of three phase fully controlled bridge converter

consists of six SCR’s. Each SCR’s are properly gated using PID controller firing

circuit to get required voltage for the motor at set rpm.

DESCRIPTION OF THE SETUP:

This setup consists of a DC motor 3HP, 220V, 1500 rpm whose speed has to

be controlled in closed loop control using PID controller & thyristorised drive.

Firing circuit is based on PID controller & power circuit is based on three phase

fully controlled rectifier. Automatically variable DC supply is provided to set the

speed of the DC motor. A speed sensor is attached to the motor shaft. A

tachometer constructed internally is provided to read the motor speed in rpm. A

pulley is attached to the shaft of the DC motor for mechanical loading

arrangement. An ammeter is provided to notice motor current. And a voltmeter is

also provided to read voltage across the DC motor.

SPEED CONTROL AND SPEED MEASURMENT:

A variable DC voltage from three phase controlled rectifier supply from PID

controller through the thyristors. The unregulated DC supply is given to the motor.

The field supply is separately excited by the single phase bridge rectifier provided

at the power circuit.

The speed sensor must be connected from motor assembly to the instrument by the

socket provided in the front panel of the control circuit. The speed sensor, sense


134

the speed of the motor and generates AC signal whose frequency is proportional to

the rpm. The digital panel meter displays the speed in rpm at the front panel of the

instrument.

SPECIFICATIONS:

THREE PHASE BRIDGE RECTIFIER:

1. Thyristors(marked as A,C & G) : 6 nos

SI.No. Parameters Ratings

1 VRRM 1200 V

2 VDRM 1200V

3 ITRMS 25 Amps

4 ITAV(180 conduction) 16Amps

2. Diode(marked as A & C) : 1 no

SI.No. Parameters Ratings

1 VRRM 1200 V

2 ITRMS 25 Amps

3 ITAV(180 conduction) 16Amps

3. Fuses:


of the instrument.

4. Field supply:

220V/2A diode bridge rectifier.

SPECIFICATIONS OF PID CONTROLLER:

1. Power : Mains ON/OFF switch to the unit with build in

indicator

2. SET RPM(Knob) : This Knob is used to set the rpm


135

3. SET RPM(Display) : This rpm indicator (display) shows the rpm set by

the knob

4. RUN RPM (Dis) : This rpm indicator (display) shows the running

rpm

5. P : This switch makes P ON/OFF

6. I : This switch makes I ON/OFF

7. D : This switch makes D ON/OFF

8. P GAIN : Used to set the gain of the p controller

9. I TIMING : Used to set the integral time I controller

10. D GAIN : Used to set the gain of the D controller

11. FEEDBACK : This socket is used to connect the speed sensor

12. ERROR OUTPUT : Shows error output

13. P OUTPUT : Shows output of P controller

14. I OUTPUT : Shows output of I controller

15. D OUTPUT : Shows output of D controller

16. PID OUTPUT : Shows output of PID controller

17. GND : Measurements are made with respect to this point.

18. Gate & Cathode : These terminals provides isolated gate pulses to SCR

19. Input N,R,Y,B, Input must be applied to these terminals for synchronization

of triggering pulses

20. R, Y, B (Test Points) : Triggering circuit testing Points.

CIRCUIT OPERATION:

This speed control unit is based on PID controller. This unit generates six line

synchronized triggering pulses. RPM can be set through knob provided on the

unit. The unit is programmed to adjust its firing angle.

The block diagram of the overall hardware is shows in fig. The feedback

sensor (proximity detector) attached to the shaft of the motor is magnetic

sensor. The sensor output goes high whenever metal screw comes near the

switch. The sensor output is connected to the input of the voltage to frequency

converts. The output of the F/V converter is proportional to running rpm. Then

the system compares the running RPM with the set RPM. If the running speed

is less than the set speed then the firing angle is decreased & if the running

speeds more than the set speed then the firing angle is increased. The system is

keeps on comparing the set speed and running speed. The three phase AC is


136

applied to the input of control circuit to generate line synchronized triggering

pulse to SCRs. These pulses are isolated by the pulse transform circuit & finally

applied to gate cathode of SCRs.

If the gain of the P controller is less than the error voltage (difference

between set & running) is more. If the gain is increased the error voltage is

reduced. The I controller further reduces the error. If the timing of I controller is

increased almost all the error is reduced. I lower the D controller has negligible

effect on overall system.

EXPERIMENTAL

HOW TO CONDUCT EXPERIMENT:

AIM: To construct a three phase fully controlled full wave bridge rectifier and

to control speed of the DC motor.

APPARATUS: 415 V input 185V output or any suitable isolation transformer,

controlled rectifier module, firing unit, DC shunt motor, patch cards etc.,

THEORY: In the bridge rectifier all the three arms of SCR’s are connected as

control switches. This is called fully controlled bridge converter. Depending on

the delay angle, the output current can be either continuous or discontinuous. In

fully controlled rectifier the load voltage may be positive or negative for

inductive loads. The power circuit & the control circuits are provided with the

manual.

PROCEDURE:

1. Connect motor terminals (field & armature) to respective points in the power

circuit & speed sensor to feedback socket.

2. Circuit connections are made as shown in the circuit diagram.

3. Connect 3 pin power cards from power unit (rectifier) to the mains supply.

4. Switch on the field supply of the motor.

5. Switch on the three phase power input.

6. Switch on the power circuit through MCB.

7. Keeping PID OFF now switch on the firing unit.

8. Set the rpm through the knob.

9. Switch on P, I, D switches, adjust the gains.

10. Load the motor up to 3 to 4A load. Note down the speed for different loads.

11. Switch off power circuit by MCB, switch off firing circuit, switch off field

supply & remove the connections.


137

TABULAR COLUMN:

Set RPM =

SL.

NO.

Load

Current

Load

Voltage

Running

Rpm

1. 0.5A

2. 1A

3. 2A

4. 3A

5. 4A

Note: Field supply must be switched on before applying voltage to armature.

Result:


138


139


140


141

EXPERIMENT 5

SINGLE PHASE CYCLO CONVERTER

INTRODUCTION:

Single phase cycloconverter unit is combination of four thyristor. A

cycloconverter is made by using two phase controlled rectifier circuits connected

anti-parallel.

A cycloconverter is used to converts input power at one frequency to output

power at a different frequency with one stage conversion. Basically,

cycloconverter are of two types namely:

1) Step down Cylcoconverter &

2) Step up Cycloconverter.

In Step-down cycloconverter, the output frequency fo is lower than the supply

frequency fo.In step-up cycloconverter, the output frequency fo is more than the

supply frequency fo. Step-down cycloconverter are discussed in this experiment.

Single phase cylcoconverter consists of a power module and a firing unit. Power

module is the combination of four SCRs and a step-down transformer. The

thysristors are mounted on individual heat sinks and protected by fast

semiconductor fuses. A well designed snubber circuit is provided for dv/dt

protection.

All the terminals of the power module are brought out to from panel through

BTI-15 terminals for connection purposes.

Firing unit generates four line synchronised firing pulses to trigger thyristors of

single phase ac voltage controller power circuit. Firing circuit is based on ramp

generator, comparator, pulse generator, pulse amplification & pulse triggering

method. Gate pulses are taken out through isolation pulse transformer. Firing

angle can be varied from 180o to0

o on gradual scale marked on the front panel.

Firing frequency can be divided by 2 &$ times the input AC signal frequency.

Firing circuit testing points are taken out to front panels. All the terminals are

brought out to front panel with BTI-15 terminals.


142

Individual devices of the power module must be interconnected externally to

form single Phase cycloconverter power circuit. Gate Pulses must be given to gate

and cathode of respective thyristors from firing unit & firing angle must be varied

to get variable load voltage.

SPECIFICATIONS:

POWER CIRCUIT:

1. SCRs (marked as A, C&G):4 nos

2. Fuses

2A replaceable fuses are provided on MF-20 sockets at the back

side of the instrument.

3. Transformer:

150-0-15V/1A is provided along with the unit.

FIRING UNIT:

Sl.No Parameters Particulars

1. Input Power Supply 230V from the mains for

synchronization and power supply.

2. Output: Four isolated gate signals for

thyristors

3 Gate drive current: 200Ma

Sl.No Parameters Ratings

1. VRRM 1200V

2. VDRM 1200V

3. ITRMS 25Amps

4. ITAV(180 Conduction) 16Amps


143

4. Firing Angle: 0o to 180

o firing angle is controlled

by potentiometer.

5. Firing Frequency Divided by 2&Divided by 4

6. Test Points 8 test points are provided for the

study of different wave forms

FRONT PANEL DETAILS:

POWER CIRCUIT:

1. Four SCRs T1, T2, T3 &T4 are placed inside and terminals are brought to

front panel and marked with their symbols.

2. Isolation Transformer is placed inside and the terminals are brought to

front

panel.

FIRING CIRCUIT:

1. Power on/off switch with LED Indicator.

2. Test points are provided by RS-2 terminals to study the different wave

forms at the different points of firing circuit.

3. 0o to 180

o firing angle control is provided by Potentiometer.

4. Firing frequency is divided by the toggle switch provided.

5. Four isolated gate pulses are connected to BTI-15 terminals on the front

panel and marked as gate & cathode.

EXPERIMENTAL:

EXPERIMENTAL BLOCK DIAGRAM:

1. Power Module Circuit connections are possible using single phase

cycloconverter power module.


144

2.Firing Unit The thyristor’s of power circuit to be triggered using

independently isolated outputs gate and cathode

pulses.

3.Load Load connections shall include The type of load is as

given below.

1.Resistance or Rheostat

RECOMMENDED FOR EXPERIMENT:

Name of the Equipment Specifications Quantity

1.Control Module: 1.Single phase

cycloconverter power with

firing unit

-1no.

2.Load: 1.Resistance-100ohms/2A -1no.

3.Measuring Instruments: Oscilloscope -1no.

4.Connecting Wires Patch cords for connecting -1no.


AIM:

To construct a single phase cycloconverter circuit and study its performance.

APPARATUS:

230V input 150V-0-15V output AC step down transformer (provided within

the unit),cycloconverter power circuit with firing circuit ,loading rheostat 100

ohms/2A.Digital multimeter,CRO,Path cards etc.

THEORY:

A cycloconverter converts input power at one frequency to output power at a

different frequency with one stage conversion.cycloconverter is used in speed

control of high power AC drives ,induction heating etc.


145

The circuit shown is for obtaining single phase frequency divided output

from a single phase AC input. One group of SCR’s produces positive polarity load

voltage and other group produces negative half cycle of the output. SCR’s T1 and

T3 of the positive group are gated together depending on the polarity of the input,

only one of them will conduct, when upper AC terminal is positive with respect to

O, SCR T1will conduct and when upper AC terminal is negative, SCR T3will

conduct thus in both half cycles of input, the load voltage polarity will be positive

by changing firing angle, the duration of conducting of each SCR (and there by the

magnitude of the output voltage) can be varied. For the sake of simplicity it is

assumed that the load is positive. Then each SCR will have a conduction angle of

(π –α) and turn off by natural commutation at the end of every half cycle of the

input. At the end of each half period of the output, the firing pulses to the SCR’s

of the positive group will be stopped and SCR’s T2 and T4 of the negative group

will be fired.


146


147

PROCEDURE

SINGLE PHASE CYCLOCONVERTER

1. The connections are made as shown in the circuit of single phase

cycloconverter with Motor Load with divided by 2 frequency.

2. The gate cathode terminals of the thyristors are connected to the

respective points on the firing module.

3. Check all the connections and confirm connections made are correct

before switching on the equipments.

4. Switch ON unit.

5. The output wave forms are seen on a CRO.

6. The firing angle is varied and AC output voltage across the load is noted.

7. A graph of Vacverses load voltage is plotted.

8. Repeat the above procedure for divided by four frequency.

EXPERIMENTAL OBSERVATIONS:

Frequency divided by 2

Sl.No Firing angle α(in degrees) Load voltage in volts

using AC voltmeter in

volts

RPM

1. 180o

2. 150o

3. 120o

4. 90o

5 60o

6 30o

7 0o

RESULT:


148


149

EXPERIMENT 6


150

SPEED CONTROL OF THREE PHASE WOUND

INDUCTION MOTOR

INTRODUCTION:

The slip-ring induction motor has a wound rotor carrying a three-phase

winding similar to that of the stator. The ends of the winding are taken to slip-

rings. If the slip ring external connections are open circuited, no current flows,

and the voltage at the slip-ring when stationary will be given by the stator

voltage times the turn ratio. if the shaft is rotated, then the voltage at the slip-

ring the current can flow as we vary the resistance the speed of the motor is

controlled.Chopper control method is more convenient. The rotor circuit with

the chopper functions as a resistance modulator. The inductance in series helps

to maintain the rotor current. The minimum speed of the motor occurs at

maximum duty cycle.

Chopper power module consists of a three phase diode rectifier, inductor and

IGBT. In addition, protections are provided for the short circuits and the fast

fuses for IGBT protections. The devices are mounted on heat sinks and

protected by fast fuses. A well designed snubber circuit is provided for dv/dt

operation

All the terminals of the power module are brought out to front panel through

BTI-15 terminals for connection purposes.

Chopper firing circuit is build in generates firing pulse ti trigger IGBT

power circuit. Firing circuit duty cycle can be controlled from 10% to 90%.it

is operated on fixed frequency variable duty cycle chopper.

Inputs must be given externally from the rotor while conducting experiment.

External load must be connected while doing experiment.

SPECIFICATIONS:

SI.No. Devices/parameters Ratings


151

EXPERIMENTAL

The chopper is used to connect & disconnect the resistance to the rotor of

the wound induction motor. when IGBT is on the rotor resistance is reduced

to zero & when the IGBT is off the rotor is connected to the external

resistance. The speed is controlled the duty cycle of the chopper.

RECOMMENDED FOR THE EXPERIMENTS:

Name of the Specifications Quantity

1

IGBT:GP30B120KD

VRRM

VDRM

ITRMS

ITAV

1200V

1200V

40 Amps

30 Amps

2

Diodes:

VRRM

VDRM

ITRMS

ITAV

1200V

1200V

40 Amps

6 Amps

3 Max.allowable average current

at any duty cycle

2 A DC

4 Duty cycle: 10% to

90%

5 Operating Frequency: fixed


152

equipment

1.input(source):

AC power

supply

Three phase auto

transformer

-1no

2.Control

Modules

Chopper Module -1no

3.output(load) Rheostat-1000 Ohms/0.4 A -1no

4.Measuring

instruments:

Oscilloscope, Tachometer -1no,-1no

5.Connecting

wires:

Patch cards for connecting

HOW TO CONDUCT THE EXPERIMENT

AIM: To control speed of three phase wound rotor induction motor

APPARATUS: Chopper module, rheostat 100 ohm/0.4A, CRO, Tachometer,

three phase wound rotor induction motor, patch cards, etc

THEORY: Three phase Diode Bridge rectifies rotor voltage to DC. Chopper

converts fixed DC voltage to variable voltage through the use of semiconductor

devices. The DC to DC converters have gained popularity in modern industry.

Some practical applications of DC to DC converter include armature voltage

control of DC motors converting one DC voltage level to another level, and

controlling DC power for wide variety of industrial processes. The time ratio

controller (TRC) is a form of control for DC to DC conversion

Time ratio controller (TRC) or chopper is basically a semiconductor

switch as shown in fig. Connected between the source and load. The switch is

closed and opened periodically such that the load is connected to, and

disconnected from, the supply alternatively. Thus the average voltage on the

load is controlled by controlling the ratio of ON state interval to one cycle

duration

The most important factor that governs the performance of the

chopper is the duty ratio. The duty ratio can be controlled in many ways, such


153

as by changing the on period duration by keeping frequency constant or by

changing frequency keepping on period constant. The third alternative method

is to change both ON period and frequency. Changing the frequency of the

chopper introduces different harmonics at different frequencies. At some

frequency of operation the harmonic contents are larger than the tolerable

limits. Therefore fixed frequency choppers with a variable on period technique

are generally used.

Chopper control method is more convenient. The rotor circuit with

the chopper functions as a resistance modulator. The inductance in series helps

to maintain the rotor current.

The minimum speed of the motor occurs at maximum duty cycle.

PROCEDURE:

1. Power circuit connections are made as shown in the circuit diagram.

Connect three phase input to the three phase auto transformer. The output of

the autotransformer terminals are connected to the respective R,Y,B stator

terminals of three phase wound rotor induction motor. The rotor terminals of

the three phase wound rotor induction motor is connected to the 3 phase

input of respective R,Y,B terminals of three phase wound rotor induction

motor control unit

2. Connect the rheostat load & CRO probe across the load. Adjust the rheostat

at suitable value

3. Keeping duty cycle knob at minimum position switch on the chopper firing

circuit,

4. Keeping auto transformer at minimum position switch on the three phase

mains. Switch on the chopper power circuit using three phase MCB.

5. Check all the connections and confirm connections made are correct before

switching on the equipments.

6. Increase the autotransformer voltage slowly for suitable value such that

motor rotates

7. Vary duty cycle of the chopper firing circuit in steps and note down

corresponding rpm.


154

8. The output waveforms are seen on a CRO

9. Plot a graph of duty cycle against speed.

TABULAR COLUMN:

SI.No Duty cycle

in%

Speed in

RPM

1. 20

2. 30

3. 40

4. 50

5. 60

6. 70

7. 80

RESULT:


155


156


157


158

EXPERIMENT 7

SINGLE PHASE FULLY CONTROLLED BRIDGE

CONVERTER

INTRODUCTION:

Single phase fully controlled bridge converter is the combination of a power

module and a firing unit.Power module consists of four SCR’s and a freewheeling

diode. In addition, protections are provided by a 6 A miniature circuit breaker

(MCB) for short circuits and four fuses for thyristor protection. The thyristors are

mounted on individual heat sinks and protected by fuses. A well designed snubber

circuit is provided for dv/dt protection.

A dc voltmeter of 250 V is provided for load voltage measurement and a dc

ammeter of 5 A is provided for load current measurement. A separate bridge

rectifier is also provided for field supply to motor loads.

All the terminals of the power module are brought out to front panel through

BIT-15 terminals for connection purposes.

Firing unit generates four line synchronized firing pulses to trigger four

SCR’S of single phase fully controlled bridge power circuit. Firing circuit is based

on ramp generator, comparator, pulse generator, pulse amplification and pulse

trigger method. Gate pulses are taken out through isolation pulse transformer.

Firing angle can be varied from 1800

to 00 on gradual scale marked on the front

panels. All the terminals are brought out front panel with BTI-15

terminals.Individual devices of the power module must be interconnected

externally to form single phase fully controlled bridge converter power circuit.

Gate pulses must be given to gate and cathode of respective SCR’s from firing unit

& firing angle must be varied from the knob to get variable load voltage.

AC inputs must be given externally through autotransformer and isolation

transformer while conducting experiment. External load must be connected while

doing experiment.This unit can be used with resistance, resistance and inductance,

motor loads.

SPECIFICATIONS:

POWER MODULE:

1. Thyristors (marked as A, C & G): 4 no


159

Sl. no. Parameters Ratings

1 VRRM 1200 V

2 VDRM 1200 V

3 ITRMS 25 Amps

4 ITAV(180 condition) 16 Amps

2. Diodes (marked as A & C): 1 no

Sl.

no.

Parameters Ratings

1 VRRM 1200 V

2 ITRMS 16 Amps

3 ITAV(180 condition) 16 mps

3. Fuses:


of the instrument.

4.Short circuit protection:

6A MCB is provided on the front panel.

5.Field supply:

INPUT: rectifier unit is directly connected to the output of the MCB

OUTPUT: rectified dc output is connected to the terminals on the

front panel.

4. Maximum allowable input voltage: -230V AC @5 A

5. Firing unit:

Sl. no. Parameters Ratings

1 Input power

supply:

230V from the mains for synchronization

and power supply


160

2 Output: Four isolated gate signals for thyristors

3 Gate drive current: 200 mA.

4 Firing angle 00 to 180

0firing angle is controlled by

potentiometer.

5 Test points: 8 test points are provided for the of

different wave forms.


POWER MODULE:

1. MCB 6A, is provided for the short circuit protection on the front panel.

2. Field supply is provided and output is connected to terminals on the front panel

and marked as ‘+’ & ‘-’.

3. Four thyristor T1, T2, T11 & T21 are placed inside the box and the terminals

are brought to front panel and marked as A for anode, C for cathode & G for

gate & symbol for each SCR is shown.

4. The terminal A for anode, C for cathode of a freewheeling diode is connected

to front panel & its symbol is shown.

5. A 0-5 A dc ammeter is provided.

6. A 0-250 V dc voltmeter is provided.

FIRING UNIT:

1. Power on/off switch with LED indicator.

2. 8 test points are provided by RS-2 terminals to study the different wave

forms.

3. 00 to 180

0 firing control is provided by potentiometer.

4. Four isolated gate pulses are connected to the BTI-15 terminals on the front

panel and marked as ‘G’ for gate & ‘C’ for cathode.

EXPERIMENTAL



161

Name of the

Equipment

Specifications Quantity

1. Input

Auto Transformer

Isolation

Transformer

Input: 0-230v

Output: 0-230V/5A

Input:0-230V

Output: 0-15-30-60-

120V/5A

-1no.

-1 no.

2. Control units: 1.Single phase fully controlled

bridge converter power Module

2. Single phase convertor firing

unit.

-1no.

-1n0.

3. Loads: 1. Resistance – 100

ohms/2A

2. Inductance–

100or250mH/3 A.

3. D.C.motor

-1no.

-1no.

-1no.

4. Measuring

Instruments

Oscilloscope, multimeter -1no.

5. Connecting

wires

Patch cards for connecting.


AIM: To construct a single phase fully controlled full wave bridge rectifier and to

observe the output wave forms with

1. R load

2. R-L load with freewheeling diode

3. R-L load without freewheeling diode


162

APPARATUS: Isolation transformer, controlled rectifier module, firing unit,

rheostat 100 ohms/2A, inductance 100 mH or 250 mH/3A, patch cards etc.

THEORY: In the bridge rectifier the entire four rectifier is the capability of wide

voltage variation between +Vdc (av) to –Vdc (av), maximum i.e. 2Vm/ π volts. Such

rectifiers find application in DC motor loads for both motoring and electrical

braking of the motor.

FULL CONTROLLED BRIDGE CONVERTER WITH R LOAD:

During positive half cycle, SCR T1 and SCR T11 are triggered

simultaneously through independent isolated gate pulses. The pair of SCR’s

conducts up to π. SCR T2 and SCR T21 are to be triggered in the next half cycle

with another pair of isolated gate pulses. The triggering angle of the pairs of SCR’s

can be varied by varying the control voltages.

For R load, the average output voltage can be found from

Vdc (av) = (1/π) αfπ Vm sinӨ dө

= (Vm/π) [-cosӨ]απ

Vdc (av) = (Vm/π) [1+cosα]

FULLY CONTROLLED BRIDGE CONVERTER FOR R-L LOAD WITH

FREE WHEELING DIODE:

When the single phase fully controlled bridge converter is connected with

RL load with freewheeling diode during positive half cycle T1 and T11

are forward

biased. When T1 and T11

fired at wt=α, the load is connected to the input supply

through T1 and T11 during period α≤wt≤π. During the period from π≤wt≤(π+α),

the input voltage is negative and freewheeling diode DF is forward biased, DF

conducts to provide the continuity of current in the inductive load. The load

current is transferred from T1 and T11 to DFand thyristor are turned off at wt=π.

During negative half cycle of input voltage, thyristor T2 and T21

are forward

biased, and the firing of T2 and T21 at wt=π+α will reverse bias DF. The diode is

turned off and the load connected to the supply through T2 and T21.

This conversion has better power factor due to the freewheeling diode.

The average output voltage can be found from


163

Vdc (av) = (1/π) α∫πVmSinӨdӨ

= (Vm/π) [-cosӨ]απ

Vdc (av) = (Vm/π) [1+cosα]

FULLY CONTROLLED BRIDGE CONVERTER FOR R-L LOAD WITH

OUT FREEWHEELING DIODE:

When the single phase fully controlled bridge converter is connected with R-

L load, during the positive half cycle thyristor T1 and T11 are forward biased and

these two thyristors are fired simultaneously at wt=α, the load is connected to the

input supply through T1 and T11. Due to inductive load T1 and T1

1 will continue to

conduct till wt=π+α, even though the input voltage is already negative. During

negative half cycle of the input voltage, thyristor are forward biased, and firing of

thyristors T2 and T21 at wt= π+α will apply the supply voltage across thyristors T1

and T11 as reverse blocking voltage. T1 and T1

1 will be turned off due to line or

natural commutation and load current will be transferred from T1 and T11 to T2 and

T21.

During the period from α to π, the input voltage Vs and input current is positive,

and the power flows from the supply to the load. The converter is said to be

operated in rectification mode. During period from π to π+α, the input voltage Vs

is negative and the input current is positive, and there will be reverse from the load

to the supply. The converter is said to be operated in inversion mode.

The average output voltage can be found from

Vdc (av) = (1/π)α∫π+α

VmSinӨdӨ

= (Vm/π) [-cosӨ]απ+α

Vdc (av) = (2Vm/π) [1+cosα]

NOTE: In case of fully controlled bridge the triggering angle should not increase

beyond αmax (approx. 1500) to allow conducting SCR sufficient time to turn off.

The maximum value of firing angle is obtained from the relation.

E= Vm sin (π+α)

There fore α=π-sin-1

(E/Vm)

Where E is the counter e.m.f. generated in the inductor.


164

PROCEDURE:

Notes:

1. Do not attempt to observe load voltage and input voltage simultaneously, if

does so input voltage terminal directly connected to load terminals due to the

no isolation of both channels of the CRO.

2. It is recommended to use low AC voltage when students are doing

experiments to eliminate electric shock.

3. Do not apply high voltage to CRO. 10:1 probe may be used while doing

high voltage measurements or use power scope.

PROCEDURE FOR R LOADS:

1. The connections are made as shown in the circuit of fully controlled

rectifier with R load using isolation transformer.

2. The gate cathode terminals of the 4 SCR’s are connected to the respective

points on the firing module.

3. Check all the connections and confirm connections made are correct

before switching on the equipments.

4. Keep the firing angle knob at 180 degree (minimum position). Switch

ON the firing unit.

5. Now switch ON the power circuit (MCB).

6. The firing angle is varied output wave form is seen on a CRO.

7. The firing angle is varied and DC output voltage and current through the

load is noted.

8. The firing angle knob at 180 degree (minimum position), Switch OFF the

power circuit (MCB) & then firing unit. Remove the patch cards.

9. Do the experiment for R-L & motor loads.

SI.

NO.

Firing angle

α in degrees

Load voltage

In volts

Load current

In Amp

1

2

3


165

4

5

RESULT:


166


167


168


169


170

EXPERIMENT 8

SINGLE PHASE HALF CONTROLLED BRIDGE CONVERTER

INTRODUCTION

Single phase half controlled bridge converter consists of a power module and a

firing unit.

Power module is the combination of two thyristor and two diodes with a

freewheeling diode. In addition, short circuit protection is provided by a 16 A

miniature circuit breaker (MCB) and four fast fuses for thyristor protection. The

thyristors are mounted on individual heat sinks and protected by fast

semiconductor fuses. A well designed snubber circuit is provided for dv/dt

protection. a dc rectifier is also provided for field supply of the motor load.

For output monitoring, a digital dc voltmeter of 200V range and a digital dc

ammeter or 2A or 20A is provided.Fr convenience of experimentation isolation of

mains must be provided. Power input is to be given through an autotransformer

and isolation transformer of suitable rating for the power circuit. All the terminals

of the power module are brought out to front panel through BTI-15 terminals for

connection purposes.

Firing unit generates two/four line synchronised firing pulses to trigger

two SCR’s of single phase half controlled bridge power circuit. Firing circuit is

based on ramp generator, comparator.pulse generator, pulse amplification & pulse

triggering method. Gate pulses are taken out through isolation pulse transformer.

Firing circuit testing points are taken out to front panels. All the terminals are

brought out to front panel with BTI-15 terminals.

Individual devices of the power module must be interconnected

externally to form single phase fully controlled bridge converter power circuit.

Gate pulses must be given ti gate and cathode of respective SCR’s from firing unit

& firing angle must be varied to get variable load voltage.

AC inputs must be given externally through autotransformer and

isolation transformer while conducting experiment. External load must be

connected while doing experiment.

This unit can be used with resistance, resistance and inductance & motor loads.


171

SPECIFICATIONS

POWER CIRCUIT:

1. Thyristors (marked as A, C & G):2 nos


1 VRRM 1200V

2 VDRM 1200V

3 ITRMS 25 Amps

4 ITAV(180 Conduction) 16 Amps

2. Diodes (marked as A&C): 3nos


1 VRRM 1200V

2 ITRMS 25 Amps

3 ITAV(180 conduction) 16 Amps

3. Fuses:

5A replacable fuses are provided on MF-20 sockets at the backside

of the instrument.

4. Sort circuit protection:

16A MCB is provided on the front panel.

5. Field supply:

INPUT: Rectifier unit is directly connected to the output of the MCB

OUTPUT: Rectified dc output is connected to the terminals on the front

panel.

6. Maximum allowable input viltage: -230v AC

FIRING UNIT:


172


1 Input power supply 230V from the mains for

synchronization and power supply

2 Output Two isolated gate signals for thyristors

3 Gate drive current 200mA

4 Firing angle: 0 to 180 firing angle is controlled by

potentiometer

5 Test points 8 test points are provided for the study

of different waveforms

6 Dimensions(w Xh

Xl):

190 mm X 110 mm X 200mm


POWER MODULE:

1. MCB 16A is provided for the input power protection on the front panel.

2. Field supply is provided and output is connected to terminals on the front

panel and marked as

‘+’ & ‘-‘.

3. Two thyristor T1, T2 are placed inside and the terminals are brought to front

panel and marked as A for anode, C for cathode & G for gate along with

their symbols.

4. The terminals of two diodes D1,D2 and a freewheeling diode Df are

connected to front panel & their symbols are marked

5. A 0-20 A dc digital ammeter is provided.

6. A 0-200V dc digital voltmeter is provided.

FIRING UNIT:

1. Power on/off switch with LED indicator.

2. 5 to 8 test points are provided by RS-2 terminals to study the different

waveforms at the different points of firing circuit.

3. 0 to 180 firing control is provided by potentiometer.

4. Two isolated gate pulses are connected to the BTI-15 terminals on the front

panel and marked as gate & cathode.


173

EXPERIMENTAL

EXPERIMENTAL BLOCK DIAGRAM

1.Auto

transformer

To suit single phase 230v/50Hz,supply input and to get 0 to

230V variable supply output.

(Used for control of input power supply so that to start with

work at low voltage and then increased to maximum rated

voltage).

2.Transformer To suit single phase 230V/50Hz with suitable supply ratio to

suit the load ratings. Isolation of main phase and neutral

with measurement circuit serves the purpose of di/dt

protection of thyristors for safe measurement of waveforms

by using an oscilloscope. Isolation of electronic noise with

mains

3.power

module

Circuits connections are possible using single phase fully

controlled bridge converter power module

4.Firing unit The thyristors of power circuit to be triggered using

independently isolated outputs Gate and cathode pulses

5.Load Load connections shall include The type of load is given

below.

1. Resistance or Rheostat

2. Resistance and Inductance,R & L.

3. D.C. Motor.


Name of the equipment Specifications Quantity

1.INPUT(SOURCE)

Auto transformer

Input:0-230V

-1 no


174

Isolation transformer

Output :0-230V/10A

Input:0-230V

Output: 0-15-30-60-120

V/5A.

-1 no

2.CONTROL

MODULES:

1.Single phase half

controlled bridge

converter power module

2. Single phase converter

firing unit.

-1 no

-1 no

3.OUTPUT(LOAD): 1.Resistance-50 ohms/5A

2.Inductance -100 or 250

mH/3A

3. D.C. motor.

-1 no

-1 no

-1 no

4.MEASURING

INSTRUMENTS:

Oscilloscope dual race -1 no

5.CONNECTING

WIRES:

Patch cords for

connecting.

HOW TO CONDUCT EXPERIMENT

AIM: To construct a single phase half controlled bridge rectifier and to observe the

output wave forms with

1. R load

2. Motor load

APPARATUS: Isolation transformer, controlled rectifier module, firing unit,

rheostat 100ohm/2A, inductance 100mH or 250 mH/3A, patch cards etc.

THEORY: The bridge rectifier with two thyristors and two diodes connected in a

control switch this is called as half controlled bridge.


175

The two thyristors are t1,t2;the two diodes are d1,d2;the third diode

connected across the freewheeling diode FD. after θ=0, T1 is forward biased only

when source voltage is Vm sinθ exceeds E. Thus, T1 is triggered at a firing angle

delay α such that Vm sinα>E.

HALF CONTROLLED BRIDGE WITH R LOAD.

During positive half cycle SCR T1 and diode D1conducts. T1 conducts from α

to π. During negative half cycle T1 is off T2 and D2conducts from π+α to 2π. Thus

there is output across the load for both the half cycles.

For R load the average out voltage can be found from

V0=1/π∫απ Vm sinθdθ

= Vm/π (1+cosα)

SINGLE PHASE HALF CONTROLLED BRIDGE WITH MOTOR LOADS.

When the single phase semi converter is connected with R-L motor load a

freewheeling diode must be connected across the load. During positive half cycle

T1 is forward biased and T1 is fired at ωt=0 .The load is connected to the input

supply through T1 and D1 during period α≤ωt≤π. During the period from

π≤ωt≤(π+α).The input voltage in negative and freewheeling diode D1 is forward

biased, DE conducts to provide the continuity of current in the inductive load. The

load current is transferred from T1 and D1 to Df and thyristor T2 is forward

biased, and the firing of T2 at ωt will reverse bias D1.The diode D1 is turned

off and the load connected to the supply through T2 and D2.

When the load is inductive and T1 is triggered. First it will conduct with D1 to pass

current through load. When supply voltage is negative, load EMF will drive

current through T1D2.This is an exponentially decreasing current. When the new

negative half cycle begins T1 is in conduction and it keep on conducting with D1

as if triggered at ωt=0.In this case load may not receive the DC power. To ensure

proper operation at the beginning of positive half cycle T2 has to be turned off and

similarly T1 should be turned off when negative half cycle begins. This is achieved

by the freewheeling diode.

` This conversion has better power factor due to freewheeling diode.

For RL load with freewheeling diode the average output voltage can be

found from


176

=1/π

= /π) [- ]

= /π) [1+ ]

PROCEDURE:

Notes

Do not attempt to observe load voltage and input voltage simultaneously. If

does so input voltage terminal directly connected to load terminals due to the

no isolation of both channels of the CRO. While using dual channels on the

CRO ensure that both the ground terminals must be connected to the same

point.

it is recommended to use low AC voltage when students are doing

experiments to eliminate electric shock

Do not apply high voltage to CRO.10:1 probe may be used while doing high

voltage measurement or use power scope

Procedure for R loads

1. The connections are made as shown in the circuit of fully controlled rectifier

with R load using isolation transformer



3. Check all the connections and conform connections made are correct before


4. Keep the firing angle knob at degree (minimum position).switch ON the

firing unit.

5. Now switch ON the power circuit switch.

6. The firing angle is varied output waveform is seen on a CRO.

7. The firing angle is varied and DC output voltage and current through the

load is noted.

8. Tabulate the practical values. (Refer given table).

9. Keep the firing angle knob at 180 degree (minimum position).Switch OFF

the power circuit& then firing unit. Remove the patch cards.

Procedure for motor loads

1. The connections are made as shown in the circuit of half controlled rectifier

with motor load.


177



3. Check all the connections and conform connections made are correct before


4. Keep the firing angle knob at degree (minimum position).switch ON the

firing unit.

5. Now switch ON the power circuit switch.

6. The firing angle is varied and the variation of the motor speed is observed.

7. Tabulate the speed in rpm for different firing angles. (refer given table).

8. Keep the firing angle knob at degree (minimum position).Switch OFF

the power circuit (MCB) &then firing unit. Remove the patch cards.

OBSERVATIONS

For R loads

SI.No Firing angle α in

degrees

Load voltage in

volts

Load current in Amp

1

2

3

4

5

For motor loads

SI.No Firing angle α in

degrees

Speed in rpm

1

2

3

4

5


178

RESULT:

MATERIALS USED:

POWER MODULE:

SI.No Components Quantity

1. Thyristor,16A/1200V, 2 nos.

2. Diode,16A/1200V, 3 nos.

3. Miniature circuit breaker

(MCB),16A

1 no.

4. IN5408 4 nos.

5. 0-20A digital ammeter 1 no.

6. 0-200V digital Voltmeter 1 no.

7. BT115 terminals 22 nos.

8. MF20 fuse holder 2 nos.

9. SCR heat sink 2 nos.

10. Diode heat sink 3 nos.

11. Capacitor,0.01uF/1000Vdc 5 nos.

12. Resistor,25E/5 watt,WWR 5 nos

13. 1 sq.mm

1200V/16A,connecting

wires

FIRING UNIT:


1. Toggle switch,3A/240V 1 no.

2. 3MM Pitch LED 1 no.


179

3. RS 2 terminals 5 nos.

4. 1 watt potentiometer 1 no.

5. BTI 15 terminals 4 nos.

6. FM 14 power

adopter/fuse holder

1 no.

7. Transformer:0-

230V/15V-0-15v

1no.

8. PCB with all components

assembled

9. 2/3 pin power mains cord 1 no.

COMPONENTS REQUIRED FOR PCB ASSEMBLING:


1. IN4007 10 nos.

2. IN4148 12 nos.

3. 5V Zener 2 nos.

4. 10K 12 nos.

5. 15K 8 nos.

6. 1K 3 nos.

7. 8.2K 1 no.

8. 4.7K 2 nos.

9. 33K 2 nos.

10. 100K 5 nos.

11. 1 M Ohm 1 no.

12. IC Base-14 pin 3 nos.

13. 330E 6 no.


180

14. 4.7K 2 nos.

15. IN4007 4 nos.

16. IN4148 2 nos.

17. 8 V Zener 4 nos.

18. 100E/0.5W 2 nos

19. 10nK63 box capacitor 4 nos.

20. 0.1K63 box capacitor 1 no.

21. 0.22UF box capacitor 1 no.

22. SL 100 1 no.

23. 470UF/25V 1 no.

24. 10UF/25V 3 nos.

25. 1000UF/25V 2 nos.

26. Regulator,7912 1 no.

27. Regulator,7812 1 no.

28. IC TL084 2 nos.

29. IC556 1 no.

30. Berg strips 2 rows.

31. SL 100 2 nos.

32. 2N2222A 2 nos.

33. 100E/5W WWR 2 nos.

34. 1:1:1 pulse transformer 2 nos.

35 Berg strips 1 row.


181


182


183

EXPERIMENT 9 V/F CONTROL OF AC DRIVE CONNECTED TO AC

MOTOR SYSTEM ON LABVIEW

AIM: To obtain V/F control of AC drive connected to AC motor system on

LabView.

APPARATUS:

i. NI LabView Software, DAQ

ii. V/F AC drive

iii. Induction motor

iv. Proximity Sensor

SPECIFICATIONS :

AC Drive Induction motor

Three phase Inverter: 0-415V AC

Armature

voltage: 415V AC

Current: 0.9Amps

Speed: 1500 RPM

Power: 0.5 HP


184

THEORY:

The Principle of Constant V/Hz for AC Induction Motor is explained as

follows:

Applied voltage to armature is proportional to frequency and air gap flux of

induction motor. i.e. V/F=Constant

If we maintain voltage to frequency ratio constant than flux in machine is constant.

And torque is independent of supply frequency. The ratio between the magnitude

and frequency of the stator voltage is usually based on the rated values of these

variables, or motor ratings. However, when the frequency and hence also the

voltage are low, the voltage drop across the stator resistance cannot be neglected

and must be compensated. At frequencies higher than the rated value, the constant

V/Hz principle also have to be violated because, to avoid insulation break down,

the stator voltage must not exceed its rated value.

The figure 9.1 shows an AC drive with V/F control concept inbuilt in the drive. By

varying controlled voltage to the drive from 0-10V speed of induction motor

connected to AC drive varies from 0 to 1500 rpm.

Fig.9.1 circuit diagram of V/F control of AC motor


185

Fig.9.2 front panel diagram of V/F control of AC motor

Fig.9.3 block diagram of V/F control of induction motor


186

Procedure:

1. Connect circuit as per circuit diagram

a.Connect supply to AC drive

b.Connect output of AC drive to armature and field supplies of

Induction motor

c.Connect speed sensor & AC drive variable point to DAQ

assistant

2.Develop LabView diagram in back panel consists of V/F nobe and

speed feedback.

3.Obtain the speed response by adjusting V/F nobe and plot the speed

response

.

.

Fig 9.4speed response of V/F control of induction motor

Result:


187

EXPERIMENT 10

CLOSED LOOP SPEED CONTROL OF DC MOTOR

USING PI, PD AND PID CONTROLLERS

Aim: To design and tune proper PI, PD & PID controllers for speed control of

DC motor drive

Apparatus:

i NI LabView Software, DAQ

ii Control design and simulation tool kit

iii Thyristorised DC drive

iv DC motor

v Proximity Sensor

Specifications:

DC Drive DC motor

Thyristorized Bridge

Rectifier: 0-220V DC Armature voltage: 220V DC

Diode Bridge Rectifier : 220V DC Current: 2Amps

Speed: 1500 RPM

Power: 0.5 HP


188

Theory:

Motion control is required in large number of industrial and domestic applications

like transportation systems, rolling mills, fans, pumps & robots etc. systems

employed for motion control are called drives. Drives employing electric motors

are called electrical drives.

Fig.10.1 Block diagram of electric drive

Fig.10.2 Circuit diagram for closed loop speed control of DC motor


189

Fig10.3 LabView front panel diagram of closed loop speed control of DC motor

Load is usually machinery designed to accomplish a given task. Usually load

requirements can be specified in terms of speed control and torque demands. A

motor having speed-torque characteristics and capabilities compatible with load

demands. Power modulator modulates flow of power from the source to the motor

in such a manner that motor is imparted speed-torque characteristics required by

load. Controls for power modulator built in control unit which usually operates at

much lower voltage and power levels.

Closed loop speed control of DC motor it consists of same elements control unit is

a computer in which control concept is implemented using LabView where auto

tuning of PID control is done to get the motor speed to reference speed or set

speed. Thyristor drive gives the required DC voltage to drive motor at desired

speed according to output voltage variable from PID controller. PID controller

adjusts the output voltage variable till the motor speed reaches desired speed.

Procedure:

1.Connect circuit as per circuit diagram

i.Connect supply to DC drive

ii.Connect output of DC drive to armature and field supplies of

DC motor.

iii.Connect speed sensor & DC drive variable point to DAQ


190

assistant.

2.Develop LabView diagram in back panel consists of reference speed,

PID controller design and speed feedback.

3.Set the reference speed to some value say 1000 RPM

4.Tune the PID controller using auto-tune block till we get desired P, I , D values.

5.Ensure that motor speed follows the set speed or reference speed.

6.Take the data to excel file from LabView, draw the set speed and actual speed on

a single plot

7.Observe the response of speed control loop using plot

8.Vary the P, I, D gains around the tune values and see the response.

9.Design the PI, PD controllers and repeat the step 3 to 8.

Fig.10.4 LabView Back panel diagram of closed loop speed control of DC

motor


191

Fig.10.5 Model graph of closed loop speed control of DC motor

Table:

Reference Speed PI gains PD gains

Table 1: Different set speeds & P, I, D gains

Result:


192

EXPERIMENT 11

CLOSEDLOOP SPEED CONTROL OF AC MOTOR-

GENERATOR SET WITH LOAD USING PI, PID

CONTROLLERS

Aim:To design and tune proper PI, PID controllers for speed control of

DC motor-generator set with load.

Apparatus:

i. NI LabView Software, DAQ

ii. Control design and simulation tool kit

iii. V/F AC drive

iv. Induction motor

v. Proximity Sensor

Specifications:



Armature

voltage: 415V AC

Current: 0.9Amps

Speed: 1500 RPM

Power: 0.5 HP


193

Theory:

Closed loop speed control of AC motor –DC generator system.It consists

of same elements present in block diagram 8.1, power modulator control

power flow from source to motor. Power modulator is a AC drive

consists of inverter where output voltage is varied based on controlled

voltage given as input to gating circuit, as input voltage varies from 0 to

10VDC drive output varies from 0-440V. Controlled voltage is

generated from closed loop with PID control implemented in LabView

based on reference speed set value. Actual speed is sensed using

proximity speed sensor and compared with reference speed an speed

error is generated, if error is positive PID controller increases controlled

voltage and if error is negative it decreases the controlled voltage till the

motor speed attains set reference speed. Saturation limiter is limits the

output voltage always in between 0 -5V even though PID controller

output varies -100 to +100. PID controller is tuned using auto tune

blocks available in control design & simulation tool boxDC generator is

connected to AC motor, which generates DC voltage according field

supply voltage to generator and motor actual speed. Loading of DC

generator is done by using lamp load, as load on generator increases

which indirectly loads the motor there by motor speed reduces.


194

Fig 11.1 Circuit diagram of closed loop speed control of AC

motor–DC generator set with load

PID control always sees the motor speed following set speed or not. As

motor speed reduces due to loading speed error becomes positive then

PID controller increases the controller voltage till motor reaches set

speed. A graph is plotted between set speed and actual speed of motor

by getting data from LabView using LVM file and drawn in Excel sheet,

we can observe variation in speed from the plot very easily. This

experimental setup can be used as constant speed drive system in

industry even load varies on the system


195

Fig 11.2. LabVIEW front panel diagram of closed loop speed control of

AC motor – DC generator set with load


196

Fig 11.3 LabVIEW block diagram of closed loop speed control of AC

motor-DC gen.set with load

Procedure:


i.Connect supply to AC drive

ii.Connect output of AC drive to armature and field supplies of

Inuction

motor.

iii.Connect field supply to DC generator

iv.Connect speed sensor & AC drive variable point to DAQ assistant

2.Develop LabView diagram in back panel consists of reference speed,

PID controller design and speed feedback.

3.Set the reference speed to some value say 1000 RPM

4.Tune the PID controller using auto-tune block till we get desired P, I ,

D values.

5.Ensure that motor speed follows the set speed or reference speed.

6.Add load on DC generator in steps

7.Take the data to excel file from LabView, draw the set speed and

actual speed on a single plot

8.Observe the response of speed control loop using plot.


10.Design the PI controller and repeat the step 3 to 9.


197

Graph:

Fig 11.4 . speed response of closed loop AC motor –DC gen. set with load

Table:

Reference Speed PI gains PD gains

P= I= P= D=

P= I= P= D=

Table 1: Different set speeds & P, I, D gain

Result:


198

EXPERIMENT 12

INDIRECT SPEED CONTROL OF AC MOTOR USING

ARMATURE VOLTAGE CONTROL WITH PI,PID

CONTROLLERS

Aim: To design and tune proper PI, PID controllers for indirect speed

control of AC motor Drive using armature V/F control method.

Apparatus:

i.NI LabView Software, DAQ

ii.Control design and simulation tool kit

iii.V/F AC drive

iv.Induction motor

v.Voltage sensor

vi.Proximity Sensor

Specifications:



Armature

voltage: 415V AC

Current: 0.9Amps

Speed: 1500 RPM

Power: 0.5 HP


199

Theory:

Speed of AC motor can be controlled by armature voltage control

method. The speed of AC motor is directly proportional to armature

voltage and inversely proportional to flux. In armature controlled AC

motor the desired speed is obtained by varying the armature voltage.

This speed control system is an electromechanical control system. The

electrical system consists of the armature. Armature circuit is taken for

analysis and the mechanical system consists of the rotating part of the

motor and load connected to theshaft of the motor.

Fig 12.1. circuit diagram of indirect speed control of AC motor with

voltage control


200

Fig.12.2 LabVIEW front panel diagram of indirect speed control with

armature voltage control

Fig1

2.3. LabVIEW block diagram of indirect speed control of AC motor

with armature voltage control


201

Procedure:


i.Connect supply to AC drive

ii.Connect output of AC drive to armature and field supplies of

Induction motor.

iii.Connect voltage sensor & AC drive variable point to DAQ

assistant 2.Develop LabView diagram in back panel consists of

reference voltage, PID controller design and voltage feedback.

3.Set the reference voltage to some value say 2 volts.

4.Run the LabView diagram Tune the PID controller using auto-tune

block till we get desired P, I , D values.

5.Ensure that motor voltage follows the set voltage or reference voltage.

6.Take the data to excel file, draw the set voltage and actual voltage on a

single plot

7.Observe the response of voltage control loop using plot


Graph:

Fig 12.4. voltage response of indirect speed control of AC motor


202

Table:

Reference Speed PI gains PID gains

P= I= P= I= D=

P= I= P= I= D=

Table 1: Different set speeds & P, I, D gains

Result:

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