VPET-106A

IGBT POWER MODULE FOR

INVERTER/CHOPPER

(Model No : VPET - 106A)

User Manual

Version 1.0

Technical Clarification /Suggestion :N / FTechnical Support Division,

Vi Microsystems Pvt. Ltd.,Plot No :75,Electronics Estate,Perungudi,Chennai - 600 096,INDIA.Ph: 91- 44-2496 3142, 91-44-2496 1852,Mail : [email protected],Web : www.vimicrosystems.com

mailto:[email protected],

CONTENTS

1. INTRODUCTION 1

2. FUNCTIONAL DESCRIPTION 2

3. THEORETICAL DESCRIPTION 14

4. STUDY OF CONTROLLER 20

5. INSTALLATION AND OPERATION 23

6. EXPERIMENTAL SECTION 26

i. STUDY OF THE PROCESS 26

ii. STUDY OF OPEN LOOP RESPONSE 28

iii. STUDY OF CLOSED LOOP RESPONSE 30

iv. TIME RESPONSE OF SECOND ORDER SYSTEM WITH P CONTROL 33

v. TIME RESPONSE OF SECOND ORDER SYSTEM WITH P+I CONTROL 37

vi. TIME RESPONSE OF SECOND ORDER SYSTEM WITH P+I+D CONTROL 41

vii. EFFECT OF DISTURBANCES ON A PROCESS 44

7. CIRCUIT DIAGRAM 46

IGBT Power Module for Inverter / Chopper VPET-106A

Vi Microsystems Pvt. Ltd., [ 1 ]

Chapter-1

Introduction



Aim

This manual is intended to give you a description of IGBT Power Module for Inverter/chopper(VPET-106A) trainer module followed by the working procedure involved with our trainermodule.

Objectives

On successful completion of this manual you should be able to :

* Understand about the IGBT Power Module for Inverter/chopper .

* Describe the Sinusoidal Pulse Width Modulation.

* Can be able to work with our module by yourself.

Features of VPET-106A

* PWM signals can be generated from any one of the various PWM controllers likeMicroprocessors, Microcontrollers, DSP, dsPIC, FPGA, etc.,

* The module can be used to study the operation of both the inverter and chopper circuit.

* Test points are provided on the front panel to view the signals at the various stages ofoperation.

* Study of various modulation techniques and study of inverter/chopper circuits can be doneby this module.

* The PWM isolation, gate driver section and signal conditioning circuits are provided in themodule.

* DC rail voltage can be directly read from the voltmeter provided in the module.



1.1 Introduction

“Power Electronics is a subject that concerns with the application of electronic principles intosituations that are rated at power level rather than signal level. For example, semiconductorpower switches such as thyristors, GTOs, MOSFETs, IGBTs work on the principle of electronics(movement of holes and electrons), but have the name power attached to them only as adescription of their power ratings”.

Power Electronics are employed in various fields that include rocket propulsion systems, motorcontrol, Electric vehicles, air-conditioners, High Voltage Direct Current (HVDC)transmission systems.

Power Electronics System

A power electronic system consists of one or more power electronic converters. A powerelectronic converter is made up of some power semiconductor devices controlled by integratedcircuits. The switching characteristics of power semiconductor devices permit a power electronicconverter to shape the input power of one form to output power of some other form.

Types of Power Electronics system

Diode Rectifiers : A diode rectifier circuit converts ac input voltage into a fixedDC voltage.

AC to DC converters : These convert constant AC voltage to variable DC outputvoltage.

DC to DC converters : A DC chopper converts fixed DC input voltage to acontrollable DC output voltage.

DC to AC converters : An inverter converts fixed DC voltage to a variable ACvoltage.

AC to AC converters : These convert fixed AC input voltage into variable AC outputvoltage.

This manual describes the IGBT POWER MODULE FOR INVERTER/CHOPPER operation



Chapter-2

About Our Trainer



2.1 Front Panel View

1. VPET-106A



2.2 Front Panel Description

Power ON/OFF switch - To switch ON/OFF power to the module.

MCB - To control input AC voltage to the power circuit.

PWM INPUT - To connect the PWM input / feedback signal from / to thecontroller unit.

R, Y, B - To connect 3? output to the load.

Voltmeter - To display DC link voltage.

P, N - To connect AC input to the module.

A+, A-, F+, (+) - To connect the DC output to the load.

RST - To reset the module.

PWM1, PWM 2...PWM 6 - Test points to view the PWM signal to the switches withrespect to ground point.

Idc, Ir, Iy, Ib - Test points to view the sensed input DC current & outputR, Y and B phase currents.

PWM Isolation - To isolate the gate signals.



2.3 Hardware Description

2.3.1 Block Diagram

The block diagram for IGBT power module consists of the following.

1. Rectifier & Filter2. Power circuit3. Controller4. Optoisolator5. Gate Driver6. Current Sensor7. Signal conditioner8. Protection Circuit.

P

N

RECTIFIER

I 3 LEG MOSFET/

DRIVER

OPTO-ISOLATIOR

PWMSIGNAL

ICURRENT

I

I

I

AC/DC

SENSOR SIGNALS

POWER CIRCUITCONDITIONER CONTROLLER

DEVICEMODULE

dc+

CO/P

I

I

I

FROM

r

y

b

dc

r

y

b

? ? ? C

VPET-105A/106A

MODULE

IGBT-



2.3.2 Block Diagram Description

1. Rectifier & Filter

The input AC voltage is rectified by the Diode Bridge Rectifier circuit. The rectified DC voltageis fed to the power circuit through a filter capacitor. The filter capacitor eliminates theunwanted ripple in the Dc input.

2. Power Circuit

The Power circuit consists of three leg IGBT circuit. IGBT switch is used as a switching devicein the power circuit. The PWM signal from the driver IC is fed to the gate of the switch. Theoutput from the power circuit is given to the load. The output may be either AC/DC dependingon the inverter/chopper mode of operation.

3. Controller

The PWM signal to the IGBT switches are generated by the controller unit. The controller maybe any processor. The PWM signal from the controller is fed to the module through the connectorprovided on the front panel. In this implementation, controller is used PWM generation.

4. Optoisolator (6N137)

The function of Optoisolator is to isolate the control circuit from power circuit. PWM signalfrom the controller is not directly fed to the power circuit in order to protect the PWM signal itis essential to provide isolation circuit between power circuit and control circuit or else the highpower components may damage the low power PWM circuit components.

5. Gate Driver (IR2110)

A IGBT drive circuit is designed to connect the gate directly to a voltage bus with nointervening resistance other than the impedance of the drive circuit switch. Gate driver acts asa high-power buffer stage between the PWM output of the control device and gates of theprimary power switching IGBT.



6. Current Sensor

IGBT power module output current is not directly fed to control (Protection) circuits. The sensorused for sensing current works on the principle of hall effect. Hence these sensors are called halleffect transducer. Hall effect transducer output current depends upon transducer primary andsecondary winding ratio. The turns ratio represents the ratio of the number of primary turns tothe number of secondary turns. A Hall effect current transducer senses the current IDC, Ir(R), Iy(Y)Ib(B).

Current Transducer

7. Signal Conditioner

The signal from the current sensor is fed back to the controller unit. The gain of the currentsignals has to be improved to achieve controller requirements. So the signal needs to beconditioned in the signal conditioner circuits.

Hall-Effect Current

Transducer TransducerCurrent

Hall-Effect Hall-Effect Current

Transducer TransducerCurrent

Hall-Effect

Idc rI Iy bI

DCI R Y B

From F1Diode Bridge Rectifier

FROM OUTPUT

(CT1) (CT2) (CT3) (CT4)



Signal Conditioner

8. Protection Circuit

In the protection circuit the DC current I dc is sensed. If the I dc value increases than the limit,the protection circuit activates and cuts the PWM to the switches in the module. The LED glowsto indicate the system shut down condition. The system can be reset by the RST press buttonprovided on the front panel. Now the LED switches OFF. Again the PWM signal should beapplied to the system.

Note: The sensing and conditioning of the output current is an optional future of thsmodule and it is of additional cost to the module.

Non-inverting Amplifier Amplifier

Inverting Comparator

IDC OffsetVoltage Gain

(TR1)

GainDCI(TR1)

ReferenceVoltage

ActiveFilter

dsPIC.CT.IN

5V

AF OUT

Idc

Gain (TR2)R-Phase

R-PhaseOffset Voltage

rIIr

yIIy

Offset VoltageY-Phase

Y-PhaseGain (TR3)

(TR3)

(TR5)

(TR7)

Gain (TR4)B-Phase

Non-Inverting Amplifier

Offset Voltage

bIIb

To dsPIC

From

Cur

rent

Sen

sor

AmplifierNon-Inverting

Non-Inverting Amplifier Amplifier

Non-Inverting

Non-Inverting Amplifier

AmplifierNon-Inverting

B-Phase



2.4 Datasheets

1. IGBT SWITCH



2. 6N137



3. IR2110



2.5 Protection and Precaution

Protection

1. Fuse is provided to protect the module from over current fault.

2. RC Snubber circuit is provided in each device to protect IGBTs.

3. MCB is provided to protect the power circuit in case of single phase AC input over voltagefault.

4. Protection circuit is provided to shut down the PWM signal to the switches at fault conditionwith LED indication.

Precaution

1. Before doing connection make all switches in OFF position.

2. Do not switch OFF IGBT power module when unit is working.

3. Do not view the input waveform and pulse waveform with CRO in dual mode.

4. Dont short output R, Y, B terminals.

5. Dont remove the PWM pulse cable when unit is in operation.



Chapter-3

Theoretical Concept(This section is solely to explain the theoretical details of IGBT Power Module for Inverter/ Chopper (VPET-106A) by considering the ideal conditions which may vary for practicalconditions. So some difference may be seen between the ideal responses to the practicalresponses of our trainer.)



The following section discusses about the three phase inverter and four quadrant chopper circuitoperation.

3.1 Inverter

Inverter is a static power converter whose objective is to produce an AC output waveform froma DC power supply. These are required in adjustable speed drives, uninterruptible power supplies,FACTS (Flexible AC transmission systems), voltage compensators etc. For sinusoidal AC output,the magnitude, phase and frequency should be controllable. A 3? Inverter is explained.

3.1.1 Three Phase Inverter Operation

In application such as uninterruptible AC power supplies and ac motor drives, three phaseinverters are commonly used to supply three-phase loads. The most frequently used three-phaseinverter circuit consists of three-legs, one for each phase. Each leg consists of 2 IGBTs so totallythis circuit uses six IGBTs. For one cycle of 360°, each step would be of 60° interval for a six-step inverter. This means that IGBTs would be gated at regular intervals of 60° in propersequence so that a three-phase AC voltage is synthesized at the output terminal of a six-stepinverter.

Basically, there are two possible modes of gating the IGBT . They are,

* 180° mode - Each IGBT conducts for 180°* 120° mode - Each IGBT conducts for 120°

But in both these schemes, gating signals are applied and removed at 60° intervals of the outputvoltage waveform. Therefore, both these modes require a six-step bridge inverter.

T6T4

T3T1

3?

-

+CV +

-s

T5

T2

D1

D2

D3

D6

D5

D2

Load

Vca

bcVVabab

c



3.1.2 Three - Phase 180° Conduction Mode

In this scheme, called the 180° mode of operation, a maximum of three IGBTs conduct at anyinstant and each IGBT conducts for ? radians in every cycle of the output. Switch pair in eachleg, i.e. T1- T4, T3- T6 and T2- T5 are turned-ON with a time interval of 180°. Same is true forlower group of IGBT. On the basis of this firing scheme, table is prepared. It is observed fromtable that in every step of 60° duration, only three IGBTs are conducting - two from upper groupand one from the lower group and vice versa.

INTERVAL IGBTs CONDUCTING

IIIIIIIVVVI

T1, T6, T5

T1, T6, T2

T1, T3, T2

T2, T3, T4

T3, T5,T4

T4, T5, T6



Gate current signals and output voltage waveforms for three phase inverter is shown below.

The switching sequence is controlled by the PWM technique. The PWM technique implementedin this module is sinusoidal pulse width modulation.

Ig

Ig

Ig

Ig

Ig

Ig

Vbn

V

t

23

4? ?

??

dcV

V

V

cnV

anV

3dcV

AB

BC

CA

0

0

0

0

0

0

0

0

0

0

0

0

I

2Vdc3

? ?

? ? ? ?432Intervals

2

6

1

2

3

4

5

II III IV V VI

3dc2V

-2Vdc3

2Vdc3

3dc-2V

Vdc

dc-V

-Vdc

t

t

t

t

t

t

t

t

t

t

t

?3 3

2? ? ?3 3

? ?



Sinusoidal Pulse Width Modulation

The switching sequence for the inverter switches in this case, is obtained by comparing asinusoidal control signal, of adjustable amplitude and frequency with a fixed frequency triangularcarrier. The frequency of the triangular carrier wave determines the switching frequency (fs) ofthe inverter switches. The frequency (f1) of the sinusoidal control signal decides the fundamentalfrequency of the inverter output voltage, and is also called the modulating frequency. Theinverter output voltage will contain voltage components at harmonic frequencies of f1. Theamplitude modulation ratio ma also called the modulation index is defined as

Where Vcontrol is the amplitude of the control signal and Vtri is amplitude of the triangular carrier,which is generally kept constant. The sinusoidal pulse width modulated wave is shown below.

Sinusoidal Pulse-Width Modulation

The output voltage of the inverter is given by,

V m VO a in? ?

where, V o = output voltage , volts.ma = modulation index. V in = input DC voltage , volts.



3.2 Chopper

In AC application, the transformer serves to convert electric power efficiently from one voltagelevel to another. Static DC to DC converters called as choppers achieve a similar function in DC.The operation of AC transformer is based on an alternating magnetic field. But in chopper thevoltage conversion is achieved by power semiconductors, which function as static switches,switching at high repetitive frequency. Choppers are widely used for traction motor control, inelectric automobiles, trolley cars, marine hoists, fork lift trucks, and mine haulers. They providesmooth acceleration control. high efficiency, and fast dynamic response.

This module uses four quadrant chopper with R-L Load for DC-DC conversion. The fourquadrant chopper is explained below.

Four Quadrant Chopper

In four quadrant operation the output current as well as output voltage can take positive ornegative values. The circuit diagram for IGBT based chopper is shown below.

Four quadrant chopper circuit.

In the first quadrant the power flows from the source to the load and is assumed to be (+)ve. Inthe second quadrant the voltage is still positive but the current is negative. The power is thereforenegative. In this case power flows from the load to the source and this can happen if the load isinductive or back emf source such as a dc motor. In the third quadrant both the voltage andcurrent are negative, but the power is positive, and the power flows from the source to the load.In the fourth quadrant voltage is negative but the current is positive. The power is thereforenegative.

The four quadrant chopper is widely used in reversible dc motor drives. The reversible dc motordrive system requires, power flow in either direction, in order to achieve fast dynamic response.By employing four quadrant chopper it is possible to implement regeneration and dynamic brakingby means of which fast dynamic response is achieved.

T4

T1

V +

-s

T3

T2

D1

D4

D3

D2

RL E+ -



Circuit Operation

Quadrant Conducting Switches Mode Description

I T1 & T4 Forward Motoring/Rectifying

Load consumespower from thesource io & Vo bothare positive.

II T4 & D2 Forward Motoring/Free wheelingoperation

Load current flow ismaintained byinductor and freewheeling diode .io &Vo both are positive.

IV D3 & D2 Inverting Load energy is fed tothe supply. io - positive.Vo - negative

III T3 & T2 Rectifying, currentflow is in oppositedirection

io & Vo both arepositive.

III T2 & D4 Free wheelingoperation

io & Vo both arepositive.

I D1 & D4 Inverting Operation Energy is fed to thesupply.io - negativeVo - positive.

Four Quadrant Chopper Operation

RegenerationIV Quadrant III Quadrant

Power Positive

II Quadrant Regeneration Power Positive

I Quadrant

o-i io

-Vo

oV

VPET-106A

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