Em-II Manual Final

ELECTRICAL MACHINES LAB - II

LABORATORY MANUAL

(III YEAR B.E. – EEE)

Prepared by

Mr. K. Balasubramaniam

Mr. M. Vijayakumar

Mr. K. Prakasam

Mr. A. Gowrishankar

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

K.S.R. COLLEGE OF ENGINEERING,

TIRUCHENGODE – 637 215

K.S.R. COLLEGE OF ENGINEERING

TIRUCHENGODE – 637 215

Reg. No.

Certified that this is the work done by Selvan / Selvi ………………….

…………………………………………... of the fifth semester Electrical & Electronics Engineering

branch during the year 2009 – 2010 in the Electrical Machines -II Laboratory.

Staff – in – charge HoD

OBSERVATION NOTE BOOK

INSTRUCTION TO THE STUDENTS

The students must read the instructions carefully and follow the same throughout

the semester.

1. Students have to go to respective lab classes according to the lab time table.

2. They have to wear the shoes and the prescribed uniform.

3. They have to know about the procedure of the experiment before start doing the

Experiment. It will be checked by the staff members.

4. After the Circuit correction in the observation note book and viva voce, they have

to get the indent slip from stores and get the required apparatus.

5. They have to give the circuit connections by involving themselves in their batch.

6. They have to take readings in proper manner without any error and get verified

from the staff.

7. They have to get signature in result within two days after completion of the

experiment.

8. They have to submit their completed previous experiment record at the time of

entering the laboratory and they should enter the mark in the log book with the

lab in-charge.

9. After completing the experiment, they have to return all the apparatus to the

stores and get back the indent slip.

10. Strict discipline is solicited inside the laboratory.

CONTENTS

S.No Date ExperimentPageNo.

MarksSign with

Date

SYLLABUS

ELECTRICAL MACHINES - II LABORATORY

LIST OF EXPERIMENTS

1. Regulation of three-phase alternator by EMF, MMF and ZPF methods.

2. Load test on three-phase alternator.

3. Regulation of three-phase salient pole alternator by slip test.

4. V and Inverted V curves of Three Phase Synchronous Motor.

5. Load test on three-phase squirrel cage induction motor.

6. Load test on three-phase slip ring induction motor.

7. No load and blocked rotor test on three-phase induction motor.

8. Separation of No-load losses of three-phase induction motor.

9. Loss summation method on three-phase induction motor.

10. Load test on single-phase induction motor

11. Determination of Equivalent circuit of single-phase induction motor

12. Speed control of three phase induction motor by V/f method

Exp. No: Date:

REGULATION OF THREE-PHASE ALTERNATOR BY EMF METHOD

AIM:

To predetermine the voltage regulation of a three phase non-salient pole alternator by EMF method.

APPARATUS REQUIRED:

S.No. Apparatus Name Range Type Quantity

1 Voltmeter(0-600)V MI 1

(0-30)V MC 1

2 Ammeter(0-2)A MC 1

(0-10)A MI 1

3 Rheostat 300Ω/1.2 A Variable 34 Tachometer - Digital 1

PRECAUTIONS:1. All the switches should be in open position while making the connection.2. Check the fuse and meters are in required specifications.3. Check all the load terminals are in off position at the time of starting.4. Keep the prime-mover filed rheostat at minimum resistance position and

alternator field rheostat at maximum resistance position at the time of starting.

PROCEDURE:

Open Circuit Test

1. Circuit connections are given as per the circuit diagram.2. Field rheostat of motor is kept at its minimum position at the time of starting.3. DPST Switch is closed. The motor is started by means of starter.4. The motor is set to run at rated speed of the alternator by varying the field

rheostat of the motor.5. The residual emf of the alternator is noted for the zero field current of the

alternator.6. Field rheostat of the alternator is gradually varied and the corresponding

induced emf and the field current is noted between 0 to 120 % of rated voltage.7. Then the field rheostat of the alternator is brought back to its original position.

i.e., the induced emf is brought back to almost zero voltage. 8. Open circuit characteristic is drawn for the above values i.e., between Eg per

phase and If .

Isc OCC

Vph rated

Field current (If) Amps

Arm

ature current , (Ia) Am

ps

SCC

Generated voltage V

ph , Volts

TABULATION

OPEN CIRCUIT CHARACTERISTICS

S.No.Field current(If) in Amps

Line voltage(Vl) in Volts

Phase voltage(Vph) in Volts

SHORT CIRCUIT CHARACTERISTICS


Short circuit current(Isc) in Amps

MODEL GRAPH

OPEN CIRCUIT AND SHORT CIRCUIT CHARACTERISTICS:

Short Circuit Test

1. In short circuit test alternator output terminals short circuited as per circuit diagram.

2. For Short circuit test TPST switch is closed.

3. Field rheostat of the alternator is varied slowly up to the rated current (short circuit current) of the alternator.

4. The corresponding field current is tabulated.

5. Short circuit characteristic is drawn for the noted values i.e., between Isc and If .

Synchronous impedance =

V ph rated

I sc for the same field current.

6. Various power factors are assumed and the phasor diagrams are drawn for both lagging and leading power factors. The voltage induced is obtained from the phasor diagrams and the voltage regulation corresponding to the power factors are calculated using the formulae.

7. Regulation characteristics i.e., power factor Vs voltage regulation are drawn for the various load currents.

FORMULAE USED

i. Synchronous impedance = Zs =

V ph rated

I sc for the same field current. Where, Voc = Rated Open circuit voltage for face, (V) Isc = Short circuit current, (A) at a Field current corresponding to the rated Voltage

ii. Synchronous reactance (Xs)

Xs = √ (Zs2−Rac2) Where, Rac = Ra (dc) X (1.6)

iii. % voltage regulation = (Eg -VT) / VT X 100

Ia

IaRaVT IaXs

Eg

φ

COMPUTATION OF ARMATURE RESISTANCE (Ra):

TABULATION TO FIND Ra

S.No.

Voltage drop across the armature

(Va) in voltsArmature Current

(Ia ) in Amps

Armature Resistance

(Ra = Va/ Ia) in ohm

Mean Ra

MODEL PHASOR DIAGRAM

(i) Lagging current

Ia

φ

VTIaRa

IaXsEg

(ii) Leading current:

VT = Rated voltage

S.No. Sin φ Cos φGenerated Voltage Eg

% Voltage Regulation

Lag Lead Lag Lead

REGULATION CHARACTERISTICS

VIVA QUESTIONS:

1. What is meant by voltage regulation?2. What is meant by Synchronous Impedance?3. What is OC test ?4. What is SC test?5. What is meant by mmf or field ampere turns?

RESULT:

Exp. No: Date:

REGULATION OF ALTERNATOR BY MMF METHOD

AIM:

To predetermine the voltage regulation of a three phase non-salient pole alternator by

MMF method.

APPARATUS REQUIRED:


1 Voltmeter (0-600)V MI 1

2 Voltmeter (0-30)V MC 1

3 Ammeter (0-2)A MC 1

4 Ammeter (0-10)A MI 1

5 Rheostat 220Ω/1.2 A Variable 3

6 Tachometer - Digital 1

PRECAUTIONS:1. All the switches should be in open position while making the connection.2. Check the fuse and meters are in required specifications.3. Check all the load terminals are in off position at the time of starting.4. Keep the prime-mover filed rheostat at minimum resistance position and alternator field

rheostat at maximum resistance position at the time of starting.

FORMULA:

% Voltage Regulation = (Eg -Vt ) / Vt X 100

PROCEDURE:1. Circuit connections are given as per the circuit diagram.

2. Field rheostat of motor is kept at its minimum position at the time of starting.

3. DPST Switch is closed. The motor is started by means of starter.

4. The motor is set to run at rated speed by varying the field rheostat of the motor.

5. The residual emf of the alternator is noted for the field current of zero value.

6. Field rheostat of the alternator is varied and the corresponding emf induced and the field currents are noted.

7. Step 6 is repeated till the emf reaches 25% more than rated voltage.

8. Open circuit characteristics are drawn for the above values i.e., between Eg per phase and If .

COMPUTATION OF ARMATURE RESISTANCE (RA):

TABULATION TO FIND Ra:

S.No.Voltage drop across

the Armature(Va) in volts

Armature Current(Ia) in Amps

Armature Resistance


Mean Ra

9. Then the field rheostat of the alternator is brought back to its original position. i.e., the induced emf is brought back to minimum voltage.

10. For Short circuit test TPST switch is closed.

11. Field rheostat of the alternator is varied and the rated current (short circuit current) is made to flow.

12. The corresponding field current is noted.

13. Short circuit characteristic is drawn for the noted values i.e., Between Isc and If . For various power factors the voltage regulations are calculated and voltage regulation characteristic is drawn.

SCC

OCC

Field current (If) Amps

TABULATION:(ii) Open Circuit Characteristics:


Generated line voltage

Vl (volts)

Generated per phase voltage

Vph (volts)

(iii) Short Circuit Characteristics:

S.No. Field Current (If) in Amps Short Circuit Current (Isc) in Amps

MODEL GRAPH :

OPEN CIRCUIT AND SHORT CIRCUIT CHARACTERISTICS

Ia

IaRaVt

Etφ

Eg

If2

If1

If

If1 – Field current corresponding to EtIf2 – Field current corresponding to IaIf – Resultant field current of If1 and If2Eg – Generated voltage per phase corresponding to field current If

O

Vt

IaRa

Et

Eg

If1

Ia

If

φ

MODEL PHASOR DIAGRAM:

1. Draw rated voltage (Vt) per phase as reference vector and then draw Ia with an angle of +

(+ for lagging power factor and – for leading power factor). φ

2. Draw a line IaRa, parallel to Ia, then join point ‘O’ and the end point of IaRa and it is known as

Et.

3. From OCC curve, find If1 for the corresponding value of Et and draw If1 normal to Et.

4. From SC curve find If2 for the value of Ia and draw If2 in phase opposition to Ia.

5. Add the current vectors If1 and If2, get the resultant field current vectors If.

6. From OCC curve find Eg for the value of If and draw Eg normal to If.

(i) Lagging power factor

(ii)

Leading power factor

Rated current = A Rated voltage per phase = V

S.No.Power Factor

Induced voltage per phase

Eg volts% Voltage Regulation

Lagging Leading Lagging Leading

REGULATION CHARACTERISTICS

MODEL CALCULATIONS

RESULT:

EXP.NO. DATE:

REGULATION OF 3-PHASE ALTERNATOR BY POTIER TRIANGULAR METHOD

AIM:To predetermine the regulation of three phase alternator by ZPF method and draw the

vector diagrams.

APPARATURS REQUIRED:

S.NO Name of the Apparatus Type Range Quantity

1 Ammeter MC 0 – 1/2 A 12 Ammeter MI 0 – 5/10 A 13 Voltmeter MC 0 – 10 V 14 Voltmeter MI 0 – 600 V 15 Rheostat Wire wound 250 Ω, 1.5 A 16 Rheostat Wire wound 1200Ω, 0.8 A 17 Tachometer Digital --- 18 TPST knife switch -- -- 1

FORMULAE USED:

Percentage Regulation=Eo−V Rated

V Rated

X 100

PRECAUTIONS:(i) All the switches should be in open position while making the connection.(ii) Check the fuse and meters are in required specifications.(iii) Check all the load terminals are in off position at the time of starting.(iv) Keep the prime-mover filed rheostat at minimum resistance position and alternator

field rheostat at maximum resistance position at the time of starting.

PROCEDURE TO DRAW THE POTIER TRIANGLE (ZPF METHOD): (All the quantities are in per phase value)

1. Draw the Open Circuit Characteristics (Generated Voltage per phase VS Field Current)2. Mark the point A at X-axis, which is obtained from short circuit test with full load armature

current.3. From the ZPF test, mark the point B for the field current to the corresponding rated

armature current and the rated voltage.4. Draw the ZPF curve which passing through the point A and B in such a way parallel to the

open circuit characteristics curve.5. Draw the tangent for the OCC curve from the origin (i.e.) air gap line.6. Draw the line BC from B towards Y-axis, which is parallel and equal to OA.7. Draw the parallel line for the tangent from C to the OCC curve.

OPEN CIRCUIT TEST:

S.No.Field

Current(If)in amps

Open circuit lineVoltage (vol)

in volts

Open circuit phase voltage (voph)in volts

8. Join the points B and D also drop the perpendicular line DE to BC, where the line DE represents armature leakage reactance drop (IXL) BE represents armature reaction excitation (Ifa).

PROCEDURE TO DRAW THE VECTOR DIAGRAM (ZPF METHOD)

1. Select the suitable voltage and current scale.2. For the corresponding power angle ( Lag, Lead, Unity) draw the voltage vector and current

vector OB.3. Draw the vector AC with the magnitude of IRa drop, which should be parallel to the vector

OB.4. Draw the perpendicular CD to AC from the point C with the magnitude of IXL drop.5. Join the points O and D, which will be equal to the air gap voltage (Eair). 6. Find out the field current (Ifc) for the corresponding air gap voltage (Eair) from the OCC

curve.7. Draw the vector OF with the magnitude of Ifc which should be perpendicular to the vector

OD.8. Draw the vector FG from F with the magnitude Ifa in such a way it is parallel to the current

vector OB.9. Join the points O and G, which will be equal to the field excitation current (If).10. Draw the perpendicular line to the vector OG from the point O and extend CD in such a

manner to intersect the perpendicular line at the point H.11. Find out the open circuit voltage (Eo) for the corresponding field excitation current (If)

from the OCC curve.12. Find out the regulation from the suitable formula.

SHORT CIRCUIT AND ZPF TEST:

S.No

Short Circuit Test ZPF Test

Field current(If)

in Amps

Rated Armature

Current (Ia) in Amps

Field current (If)

in Amps

Rated Armature

Current (Ia) Amps

Rated Armature

Voltage (Va) in Volts

W1 in Watts W2 in WattsTotal Power in Watts

Act. = (Obs. X MF)

Act. = (Obs. X MF)

(W1+W2)

MF

VIVA QUESTIONS:

1. What is meant by ZPF Test?

2. What is Poitier reactance? How is it determined by Poitier triangle?

3. What is meant by armature reaction reactance?

4. What is the significance of the ASA modification of MMF method?

5. What is air gap line in Poitier method?

RESULT:

Exp. No: Date:

LOAD TEST ON THREE-PHASE ALTERNATORAIM:

To conduct a load test on three phase alternator and to draw the following

characteristics

a) voltage regulation curve b) output Vs efficiency curve

APPARATUS REQUIRED:

Serial No.

Name of the apparatus

Range Type Quantity

1.

2.

3.

4.

5.

Voltmeter

Ammeter

Rheostat

Tachometer

Three phase Loading Unit

(0-600V)

(0-250V)

(0-50A)

(0-2A)

(0-10A)

220 /1.2AΩ

-

5KW

MI

MC

MC

MC

MI

Variable

Digital

Resistive

1

1

1

1

1

3

1

1

PRECAUTIONS:1. All the switches should be in open position while making the connection.2. Check the fuse and meters are in required specifications.3. Check all the load terminals are in off position at the time of starting.4. Keep the prime-mover filed rheostat at minimum resistance position and alternator field

rheostat at maximum resistance position at the time of starting.PROCEDURE:

1. The connections are made as per the circuit diagram and the DPST is closed.2. Start the motor with the help of three point starter.3. By adjusting the field rheostat of motor, run the alternator at synchronous speed.4. The alternator field rheostat resistance is adjusted and set the voltmeter reading to rated

voltage of the alternator.5. At no load take the readings of voltmeter, ammeter.6. Now, close the TPST switch and apply the load. Look for any change in the speed and

voltage if so brings back to the previous values. Now take the corresponding reading of ammeter.

7. Now open TPST switch and note down the alternator side voltage reading as Eg and immediately the TPST is closed.

8. Repeat the above procedure until the machine is loaded up to 120% of rated current.

TABULATION:

S.No

MOTOR ALTERNATOR

Input voltage (Vm) in Volts

InputCurrent(Im) inAmps

Input power(Wmi)

in Watts

Output power (Wmo)

inWatts

Load voltage (VA) in Volts

Load current

IA in Amps

Output power

=√3VLIL

Cosφ in

watts

Field winding voltage (Vf) inVolts

Field winding current

(If) in Amps

Field winding

input(VLIL)

In Watts

Input to the

alternator in watts

% Efficiency

η

% Voltage regulation(Eg-Vr)/Vr

*100

FORMULA USED:

Motor Input Power = Vm Im

Motor Output Power = ηmVmIm [Assume motor efficiency]

Input to the Field Winding = Vf If

Alternator Input Power = Motor Output Power + Input to the Field Winding

Alternator Output Power = √3VLILCos [Where Cos = 1]φ φ

% of Alternator Efficiency (ηA) = (Output Power/ Input Power)X100

% Voltage Regulation = [(Eg1-Vr) / Vr]X100 %

MODEL CALCULATION:

VIVA QUESTIONS:

1. What is meant by direct axis reactance?

2. What is meant by quadrature axis reactance?

3. How the regulation of alternator is predetermined?

4. What is the difference between salient pole alternator and cylindrical rotor type alternator?

5. What is the purpose of damper winding?

RESULT:

Exp. No: Date:

REGULATION OF THREE-PHASE SALIENT POLE ALTERNATOR BY SLIP TEST

AIM:To predetermine the voltage regulation of the given three-phase alternator by slip

test.

APPARATUS REQUIRED:

S.No.Apparatus

NameRange Type Quantity

1 Voltmeter

(0-600) V MI 1

(0-100) V MI 1

(0-30) V MC 1

2 Ammeter (0-10) A MC 1

(0-10) A MI 1

3 Rheostat 220 / 2.2 AΩ Variable 1

PRECAUTIONS:1. All the switches should be in open position while making the connection.2. Check the fuse and meters are in required specifications.3. Check all the load terminals are in off position at the time of starting.

PROCEDURE:

1. Circuit connections are given as per the circuit diagram.

2. After closing the DPST switch, the motor is started by using three point starters.

3. Now the alternator is made to run at a speed slightly less than synchronous speed using field rheostat of the motor.

4. By using the three phase auto transformer, a low voltage is applied across the stator of the alternator. Suppose, if the voltmeter across the field winding, reads some value, then change the direction of rotation of the alternator or if the same voltmeter reads zero, then the speed of the alternator and voltage applied are slightly adjusted in such a manner that the pointer in the voltmeter and ammeter of the alternator oscillates with maximum and minimum amplitude.

5. The maximum and minimum values of the readings of both the meters are noted.

TABULATION

Minimum Voltage in

Volts

Maximum voltage in

Volts

Minimum current in

Amps

Maximum current in

Amps

Xsd inΩ

Xsq in Ω Xsd/Xsq

Ia = Amps

Sl.No. Power factorEo in Volts % Regulation


Ia = Amps

Sl.No. Power factorEo in Volts % Regulation


MODEL CALCULATION

Maximum voltage/ph. = Vmax /√3

Minimum voltage/ph. = Vmin /√3

Synchronous reactance of direct axis Xsd = (Max. voltage/Ph.) / (Min.current/ph.)

Synchronous reactance of quatrature axis Xsq = (min. voltage/ph) / (max.current/ph.)

% Regulation = (E0 – Vph.) / Vph. X 100

COMPUTATION OF ARMATURE RESISTANCE (RA):

TABULATION TO FIND Ra:

S.No.

Voltage drop across the Armature(Va) in Volts

Armature Current

(Ia) in Amps

Armature Resistance


Mean Ra

Average value of Ra = --------- Ω Ra.c = Rd.c * 1.1 = ------- Ω

REGULATION CHARACTERISTICS:

PROCEDURE TO DRAW THE VECTOR

DIAGRAM

Assume rated voltage ‘V’ per phase as the reference vector and mark the endpoint as ‘a’.

Draw a line ‘la’ lags the voltage ‘V’ by an angle ‘’.

From point ‘a’ draw a drop ‘laRa’ in parallel with ‘la’ and mark it as point ‘b’.

From point ‘b’ draw a drop ‘laXq’ in quadrature with ‘la’ and mark it as point ‘c’

Join the points ‘o’ & ‘c’.

The angle between oc & ‘V’ is ‘’ and the angle between oc & ‘la’ is’ ’.

Draw the currents ‘Iq’ & ‘Id’ where ‘Iq‘ & ‘Id’ are quadrature & direct components of Ia

where Iq =la cos, Id = la sin

From point ‘b’ draw a line IdXd in quadrature with ‘Id’ and mark it as point‘d’. From point‘d’ draw a line IqXq in quadrature with ‘Iq’ and mark it as point ‘e’.

Join the points ‘o’ and ‘e’ it will give the value of the generated voltage ‘Eo’ per phase

Ф

Ia Xq

IdXd

e

d

cEo

bIaRa

aVPhδ

Iq

IaId

o

VECTOR DIAGRAM FOR 0.8 PF LAGGING

VIVA QUESTIONS:

1. What is the purpose of slip test on 3 phase alternator?

2. Define Slip

3. How is the regulation of alternator predetermined by slip test?

4. What is the purpose of damper winding?

RESULT

Exp. No: Date:

V AND INVERTED V CURVES OF THREE PHASE SYNCHRONOUS MOTOR

AIM:

To draw ‘V’ and inverted ‘V’ curves of a given three phase synchronous machine.

APPARATUS REQUIRED:


1. Voltmeter (0 – 300 V) MC 1

(0 – 600 V) MI 1

2. Ammeter

(0 – 2A) MC 1

(0 – 20A) MC 1

(0 – 10A) MI 1

3.Rheostat 50Ω/4.9A Variable 1

360 Ω / 1.1A Variable 3

4. Watt meter 300V/10A UPF 1

5. Power Factor meter 600V/10A Analog 1

6. Synchronizing switch - Manual 1


PROCEDURE

1. Connections are made as per the circuit diagram.

2. DPST switch is closed and DPDT switch is thrown to position – 1.

3. Now the armature rheostat of the motor is brought to its minimum resistance position. At this instant the SPST switch is closed.

TABULATION

1. at no load condition

S.No.Vdc in Volts

Field current

(If) in Amps

Vac in Volts

Iac in Amps

Wattmeter reading W1

in Watts

Power W1 x MF

in Watts

Power Factor

* MF is the watt meter multiplication factor

2. at any load condition

S.No.Vdc in Volts

IL in Amps

Field current

If in Amps

Vac in Volts

Iac in Amps

Wattmeter reading W2

in Watts

PowerW2 x MF

in Watts

Power Factor

* Where MF is the watt meter constant

4. The field rheostat resistance of the motor is adjusted so that the motor runs at nearly to its synchronous speed.

5. The supply voltage on the alternator side is measured.

6. By varying the filed rheostat resistance of the alternator the generated voltage is made equal to the supply voltage of the three phase side.

7. Now the TPST switch is closed and the lamp flickers. By adjusting the filed rheostat of the motor, bring the frequency of the flickering to very minimum. During the dark period, the synchronous switch is closed. Now the synchronous machine is synchronized with the main supply.

8. Now the DPDT switch is opened.

9. By varying the field rheostat resistance of the alternator, find the point where the field current is low and armature current in approximately 110% of the full load current. Note down all the meter readings.

10. Gradually move the rheostat resistance position such that, the field current increases and the alternator armature current decreases. Note down the readings for various armature currents. At one stage, the field current will still increase and the armature current will also increase. Take the readings up to the 110% of rated current of the armature.

11. Now DPDT switch is thrown to position – 2. Apply some load on the DC generator.

12. Repeat the previous procedure.

13. Draw the curves between field current Vs power factor and field current Vs armature current.

MODEL GRAPH:

VIVA QUESTIONS:

1. Why Synchronous motor is not self starting?

2. What are the starting methods used for synchronous motor?

3. List the application of Synchronous motor?

4. What are the readings considered for inverted V curve?

5. What is synchronous condenser?

RESULT:

Exp. No: Date:

LOAD TEST ON THREE-PHASE SQUIRREL CAGE INDUCTION MOTOR

AIM:

To conduct the load test on the given three phase squirrel cage induction motor and

to draw its performance characteristics.

APPARATUS REQUIRED:

S.No. Apparatus Range Type Quantity

1. Voltmeter (0-600)V Ml 1

2. Ammeter (0-10) A Ml 1

3. Wattmeter 600 V, 10A UPF 2

4. Tachometer -- Digital 1


PROCEDURE


2. After closing the TPST switch, motor is started by using star-delta starter.

3. Note down the no load readings of V1, I1, W1, W2, S1, S2 and N.

4. By applying the load, take different readings till the current reaches 120% of the rated current.

5. Using the formula, efficiency, torque, power factor and slip are calculated and the curves are plotted.

TABULATION

S. No

.

Line Voltage (VL) inVolts

Load current (IL) inAmps

Spring balance Readings (Kg)

Speed (N) in

RPM

Wattmeter readings

Input power (Pt) in

Watts

Torque (T) in

N-m

Output power (Po) in

Watts

Power factor

% Slip (S)

% Efficiency

()S1 S2 S1~ S2 W1xMF W2xMF

FORMULAE USED

1. Input Power (Pi) = (MF x W1 + MF x W2) watts

2. Torque (T) = 9.81 * (S1 ~ S2) * Reff N-m

3. Output Power (Po) = 2 N T / 60 wattsπ

4. Efficiency () = (Output Power / Input Power)* 100

5. % of Slip (S) = (Ns – N / Ns) X 100

6. Power Factor = Input Power / (√3

* VL *IL)

Where,

S1, S2 Spring balance readings in Kg.

Reff Effective radius of the brake drum in meters.

Reff = (Brake drum radius in cm + ½ of thickness of belt in cm)

T Torque in N-m

N Speed in RPM

Ns Synchronous speed in RPM

MF Multiplication factors of wattmeter

MODEL GRAPH

MODEL CALCULATION

VIVA QUESTIONS:

1. What is meant by RMF?2. Why an induction motor is called rotating transformer?3. Why an induction motor will never run at its synchronous speed?4. What are slip rings?5. What are the advantages of cage motor?6. What is meant by magnetic logging?

RESULT

Exp. No: Date:

LOAD TEST ON THREE-PHASE SLIP RING INDUCTION MOTOR

AIMTo conduct a load test on slip ring induction motor and draw its performance characteristics.

APPARATUS REQUIRED

S.No.Name of the apparatus

Range Type Quantity

1. Voltmeter (0 -600)V MI 1

2. Ammeter (0-10A) MI 1

3. Wattmeter 600V/10A UPF 2

4. Tachometer ---- Digital 1

PROCEDURE

The connections are made as per the circuit diagram.

The rotor resistance starter should be at the maximum resistance position.

The TPST switch is closed.

The rotor resistance starter is adjusted by means of step by step and bring it in to

minimum resistance position.

At no load take the readings of voltmeter, ammeter and wattmeter and also the speed in

RPM

Load the machine up to 120% of full load and note down all the meter readings.

TABULATION:

S.No

Line voltage (VL) in Volts

Line current (IL) in Amps

Speed (N) in rpm

Wattmeter readings in Watts

Spring balance readingin kgs. Torque

(T) in N-m

% slip(S)

Power factor

Output power

inWatts

% Efficiency

( )ηW1 x MF

W2 x MF

W1+W2 S1 S2 S1~S2

Without External

Resistance

With External

Resistance

Release the load fully and bring the machine to off position.

Repeat the above procedure when external resistance is included in the rotor circuit.

FORMULA:

i). Input power Pin = W1 + W2 in watts

Where,

W1, W2 - wattmeter readings in watts

ii). Torque T = 9.81x (S1~S2) x Reff. N-m

Where, S1, S2 - Spring balance readings in Kgs

Reff - Effective radius of brake drum in m

iii). Output power Po= (2 NT) / 60 in wattsπ

Where, N - Speed of rotor in rpm T - Torque in N-m

iv). % Slip = ((NS-N) / NS) x100

Where,

Ns - Synchronous speed in rpm

v). % efficiency ( ) = (Output power / Input power) x 100η

vi). Power factor (cos ) = Input power / (√3Vφ L IL)

Where,

VL - Supply voltage in volts IL - Line current in amps

VIVA QUESTIONS:

1. Mention different types of speed control of slip ring induction motor?2. What is meant by crawling of induction motor?3. What are the advantages of 3-phase induction motor?4. What is the difference between slip ring and split ring?5. What is reason for inserting additional resistance in rotor circuit of a slip ring induction

Motor?

RESULT:

Exp. No: Date:

NO LOAD AND BLOCKED ROTOR TEST ON THREE-PHASE INDUCTION MOTOR

AIM

To predetermine the performance characteristics of a three phase squirrel cage

induction motor from equivalent circuit and circle diagram approach.

APPARATUS REQUIRED

S.No.Apparatus

NameRange Type Quantity

1. Ammeter

0-5A MI 1

0-15A MI 1

0-15A MC 1

2. Voltmeter

0-600V MI 1

0-150V MI 1

0-30V MC 1

3. Wattmeter600V/5A LPF 2

150V/20A UPF 2

PRECAUTIONS

TPST should be opened before verifying the circuit connections

Autotransformer should be in the minimum voltage position

TABULATIONS

NO LOAD TEST

Line Voltage

(VL)in Volts

Line Current

(Ia)in Amps

Wattmeter reading in Watts No load input

Power in Watts= W1 +W2

Speed (N)in rpm

W1 x MF W2 x MF

BLOCKED ROTOR TEST

Line Voltage(VL) in Volts

Line Current

(Ia)in Amps

Wattmeter reading in Watts Copper loss in

Watts= (W1 + W2)W1 X M.F W2 X M.F

TO FIND STATOR RESISTANCE

S.No.

Voltage drop in the stator

(V)in Volts

Stator current (Is)

in Amps

Stator resistance(Rs = V / Is)

in Ω

Mean (Rac)

Stator resistance R1 = Rac x 1.6 in Ω

PROCEDURE

NO LOAD TEST

The connection are made as shown in the circuit diagram

After observing all precautions the TPST switch is closed

By adjusting autotransformer bring the voltmeter reading to rated voltage of the motor

then note down voltmeter, the ammeter and the wattmeter readings.

BLOCKED ROTOR TEST

Block the rotor by applying a load

After observing all the precautions the TPST switch is closed

By gradually adjusting the auto transformer bring the ammeter reading to the rated current of the motor then note down ammeter, voltmeter and wattmeter readings

TO FIND THE STATOR RÉSISTANCE

The connection are made as shown in the circuit diagram

Apply different voltage to stator winding up to the full load current note down the ammeter and the voltmeter readings

FORMULAE

NO LOAD TEST

No load line voltage = V0 in Volts

No load line current = I0 in Amps

No load power = W0 in Watts

BLOCKED ROTOR TEST

Blocked rotor line voltage = Vsc in Volts

Blocked rotor line current = Isc in Amps

Blocked rotor power = Wsc in Watts

No load voltage per phase V0 = VL0 in V

No load current per phase I0 = IL0 / √3 in A

No load power per phase W0 = WL0 / 3 in W

Blocked rotor voltage per phase Vsc= VLsc in V

Blocked rotor current per phase Isc = ILsc / √3 in A

Blocked rotor power per phase Wsc = WLsc / 3 in W

Cos ф0 = Wo / V0 I0

ф0 = Cos -1(Wo / V0 I0)

Find Sin ф0

Magnetizing branch resistance R0 = V0 / (I0 Cos ф0) in Ω

Magnetizing branch reactance X0 = V0 / (I0 Sin ф0) in Ω

Total resistance Rsc = Wsc / Isc2 in Ω

Total impedance Zsc = Vsc / Isc in Ω

Total reactance Xsc = √ Zsc2- Rsc

2 in Ω

X1 = X21 = Xsc / 2 in Ω

R21 = Rsc – R1 in Ω

Where

X1 - Stator reactance in Ω

X21 - Rotor reactance referred to stator in Ω

R1 - Stator resistance in Ω

R21 - Rotor resistance referred to stator in Ω

For any slip ‘S’, RL = R21 (1 - s) / s in Ω

Z = (R1+ R21 / s) + j(X1 + X2

1 /s) in Ω

I11∟ф1 = (V∠0 ° / Z) in A

No load current per phase = I0∟ф in A

TABULATION FOR EQUIVALENT CIRCUIT METHOD

MODEL GRAPH (EQUIVALENT CIRCUIT)

S. No.

Line Voltage (VL) in Volts

% Slip(assume)

Speed(N) in RPM

Phase current(IPh) in Amps

Line current(IL) in Amps

Input power(Pt) in Watts

Output power(Po) in Watts

Torque (T) inN-m

Power Factor

% Efficiency

( )η

I1 = I0∟ф+ I11∟ф1

= I ∟ in Aф

Line current IL = √3 I in A

Power factor = Cos ф

Speed = NS (1 - s) in rpm

Input power = 3 x Vph x Iph x Cos in Wф

Output power = 3 x (I’1)2 x RL in W

%Efficiency=Output PowerInput Power

X 100

Torque=(I ¿¿11 x R21/s )/(2 x π xns)∈Nm¿

Where ns – synchronous speed in rps

Repeat the above calculation for various slips.

MODEL GRAPH (CIRCLE DIAGRAM)

VIVA QUESTIONS:

1. What is purpose of Equivalent circuit?2. What is meant by crawling of induction motor?3. How will you calculate Cu loss of 3-phase induction motor?4. How will you calculate core loss of 3-phase induction motor?5. List out the starting methods for 3 phase induction motor.

RESULT:

Exp. No: Date:

SEPARATION OF NO-LOAD LOSSES OF THREE-PHASE INDUCTION MOTOR

AIM

To separate the no load losses of a three-phase induction motor to its components

a) Iron loss

b) Mechanical loss

APPARATUS REQUIRED

S.No Apparatus Range Type Quantity

1. Voltmeter0-600 V MI 1

0-30 V MC 1

2. Ammeter 0-5 A MI 1

0-10 A MC 1

3. Watt meter 600 V/5 A LPF 2


PROCEDURE

The connections are made as per the circuit diagram.

By adjusting the autotransformer, the rated voltage is applied.

The readings of Voltmeter, Ammeter and Watt meters (W1W2) are noted.

By adjusting the autotransformer, apply slightly less than the previous voltage and the meter readings are noted.

Repeat the above procedure until the voltmeter reads the minimum voltage.

A graph connecting Vph2 Vs No Load Loss is drawn. From the curve mechanical loss and iron loss at rated voltage are calculated.

S.No

Line voltage (VL) in Volts

Line current (IL) in Amps

Phase current (Iph) in Amps

Vph2

Watt meter reading in

Watts No load input Power in Watts

( W1+ W2)

Copper loss in Watts

No load loss in Watts

Mechanical loss (Wm) in

Watts

Iron loss (Wi )

in WattsW

1xMF W

2xMF

TABULATION – SEPARATION OF NO LOAD LOSSES

FORMULA

No load losses = No load input – No load Cu loss

NoLoad Losses=K1W 1+K2W 2−3 I o2 x Ra

VIVA QUESTIONS:

1. What are losses in 3-Phase induction motor?2. How will you separate losses of induction motor?3. What is meant by Hysteresis loss?4. What is meant by Eddy Current loss?5. How to minimize the eddy current and hysteresis losses?

RESULT:

Exp. No: Date:

LOSS SUMMATION METHOD ON THREE-PHASE INDUCTION MOTOR

AIM

To predetermine the performance characteristics of a given 3 phase induction

motor by loss summation method.

APPRATUS REQUIRED


1. Voltmeter

0 – 600 V MI 1

0 – 150 V MI 1

0 – 30 V MC 1

2. Ammeter 0 – 10 A MI 1

0 – 10 A MC 1

3.Wattmeter 600 V / 10 A UPF 2

150 V / 10 A UPF 2


PROCEDURE

NO LOAD & LOAD TEST

Connections are made as per the circuit diagram.

By adjusting the autotransformer the rated voltage is applied.

The NO LOAD readings of Voltmeter, Ammeter and Watt meters (W1, W2) are noted.

Now the motor is gradually loaded and the corresponding readings are noted.

This procedure is repeated till 125% of rated current is obtained.

Note: The brake drum spring balance readings are ignored.

BLOCKED ROTOR TEST

Connections are made as per the circuit diagram.

The rotor is blocked.

The autotransformer is adjusted such that the ammeter reads the same value of current as in the load test (i.e. rated current) and the corresponding readings of Voltmeter and Watt meters (W3, W4) are noted.

TABULATION – LOSS SUMMATION METHOD

S. No

Line voltage (VL)

in Volts

Line Current

(IL) in Amps

Speed (N) in rpm

Wattmeter readings in watts

Input power (W)

(W1+ W2) in Watts

Cu loss (W)

(W3+ W4) in Watts

Output power in

Watts

Torque (T) in N-

m

Power factor

% Slip

% Efficienc

yMF x W1

MF x W2

MF x W3

MF x W4

FORMULAE

Constant losses (Wo) = No load input – No load Cu loss

No load input – 3 I02 * Ra

Input power = W1 + W2

Cu loss = W3 + W4

Output power = Input power – Cu loss – Constant loss

= (W1 + W2) – (W3 + W4) – W0

Torque (T) = (Output / 2N) * 60 N – m

Slip (%) = (Ns – N) / Ns * 100

Power Factor = Input / (3 VL *IL)

Efficiency (%) = (Output / Input) * 100

VIVA QUESTIONS:

1. Why the three phase induction motor is called as rotating transformer?2. How will you separate losses of induction motor?3. What is the relationship between load current and loss?4. Why the induction motors are generally called as asynchronous motor?5. Name the applications of 3 phase squ. Cage induction motor?

RESULT

Exp. No: Date:

LOAD TEST ON SINGLE-PHASE INDUCTION MOTOR

AIM

To conduct the load test on single phase capacitor start induction motor and to

draw the performance characteristics curve.

APPARATUS REQUIRED


1. Voltmeter 0-300V MI 1

2. Ammeter 0-20A MI 1

3. Wattmeter 300V/20A UPF 1

4. Single Phase Auto Transformer230V/(0-270)V,

20AVariable 1

5. Tachometer - Digital 1


PROCEDURE

The connections are made as shown in the circuit diagram.

The supply is given and the DPST switch is closed.

By adjusting autotransformer, bring the voltmeter reading to rated voltage of the motor.

Under no load condition note down all the meters reading.

Now apply the load in step by step up to the 125% of rated current, note down all the readings of the meters.

TABULATION

S.No.

Supply voltage (Vs) in

Volts

Line current (IL) in

Amps

Input power

(W1xMF)

(Watts)

Speed

(N) in rpm

Spring balance reading in kg

Torque

(T) in N-m

Output power

(Po) in Watts

% Slip

Power Factor

% Efficiency

S1 S2 S1~ S2

FORMULAE

1. Torque = 9.81 (S1 ~ S2) * Reff in N-m

Where S1, S2 - Spring balance reading in Kg

Reff - Effective radius of the brake drum in metre.

2. Output power = 2 NT / 60 in wattsπ

3. % Slip = (Ns – N) / Ns * 100

Where Ns - Synchronous speed of the machine.

N - Rotor sped of the machine.

4. Power Factor = Input power / VLIL

5. % Efficiency = (Output power / Input power) * 100

VIVA QUESTIONS:

1. What are the various methods available for making a single-phase motor self-starting?

2. What is the function of capacitor in a single-phase induction motor?

3. State any four use of single-phase induction motor.

4. State the advantages of capacitor start- run motor over capacitor start motor.

RESULT

Exp. No: Date:

DETERMINATION OF EQUIVALENT CIRCUIT OF SINGLE-PHASE INDUCTION MOTOR

AIM:To draw the performance characteristics of a single phase induction motor by

conducting the no-load and blocked rotor test.

APPARATUS REQUIRED:

S.NoName of

ApparatusRange Type Quantity

1 Voltmeter(0-300)V

MI1

(0-150)V 1

2 Ammeter(0-10)A 1(0-2)A 1

3 Wattmeter(330V,10A) UPF 1(300V,5A) LPF 1

THEORY:

A 1- induction motor consists of stator, rotor and other associated parts. In theФ

rotor of a single phase winding is provided. The windings of a 1- winding(provided) areФ

displaced in space by 120º.A single phase current is fed to the windings so that a resultant

rotating magnetic flux is generated. The rotor starts rotating due to the induction effect

produced due to the relative velocity between the rotor winding and the rotating flux.

PRECAUTIONS:NO LOAD TEST:

Initially DPST Switch is kept open. Autotransformer is kept at minimum potential position. The machines must be started on no load.

BLOCKED ROTOR TEST:

Initially the DPST Switch is kept open. Autotransformer is kept at minimum potential position. The machine must be started at full load(blocked rotor).

PROCEDURE:

NO LOAD TEST:

1. Connections are given as per the circuit diagram.2. Precautions are observed and the motor is started at no load.3. Autotransformer is varied to have a rated voltage applied.

BLOCKED ROTOR TEST:

1. Connections are given as per the circuit diagram.2. Precautions are observed and motor is started on full load or blocked rotor

position. 3. Autotransformer is varied to have rated current flowing in motor.4. Meter readings are the noted.

Reff = 1.5*Rdc

FORMULAE-

NO LOAD TEST- cos = Wo/VoIo Ф Iw = Io cosФ Im = Io sin Ф Ro = Vo/Iw Xo = Vo/Im

BLOCKED ROTOR TEST-

Zsc = Vsc/Isc ΩRsc = Wsc/Isc2 ΩXsc = √(Zsc2 – Rsc2) Ω

TABULATION

NO LOAD TEST

S.No.No Load

Voltage (Vo) in volts

No Load Current

(Io) in amps

No Load Power (Wo) in watts

Actual = Observed x MF

BLOCKED ROTOR TEST

S.No.Short Circuit

Voltage (Vsc) in volts

Short Circuit

Current (Isc) in amps

Short Circuit Power (Wsc) in watts

Actual = Observed x MF

VIVA QUESTIONS:

1. What are losses in Single Phase induction motor?2. Name the types of single phase induction motor?3. What is the purpose of centrifugal switch?

4. State any four use of single-phase induction motor.

RESULT-

Exp. No: Date:

SPEED CONTROL OF THREE PHASE INDUCTION MOTOR BY V/F METHOD

AIM

To control the speed of a given Three-Phase Induction motor by V/f method and to

draw the characteristics curves.

APPARATUS REQUIRED

S. NO Name of the Apparatus Type Range Quantity

1 Voltmeter MI 0-600V 1

2 Three-Phase Autotransformer Variable 415V / (0-600)V 1

3 Tachometer Digital - 1

PROCEDURE

VOLTAGE CONTROL METHOD

1. Connections are given as per the circuit diagram.

2. Using the three-phase autotransformer motor is started to run.

3. The three-phase autotransformer is varied gradually and the corresponding voltage

and speed are noted up to 120% of the rated speed.

4. The motor is switched off using the TPST switch after bringing autotransformer is

their initial position.

TABULATION FOR VOLTAGE CONTROL METHOD

Speed (N) in r.p.m

S.NOAPPLIED VOLTAGE

in VoltsSPEED IN RPM

(N)

MODEL GRAPH:

Vin in volts

VOLTAGE CONTROL METHOD:


2. Field rheostat of motor is kept at its minimum position at the time of starting.

3. DPST Switch is closed. The motor is started by means of starter.

4. The motor is set to run at rated speed of the alternator by varying the field rheostat of the motor.

5. Field rheostat of the alternator is gradually varied and set the rated voltage.

6. Then the field rheostat position of the motor is varied. i.e., the frequency of the induced emf also changed.

7. This induced voltage given to the induction motor.

8. For different frequency speed of the induction motor reading is noted.

TABULATION FOR VOLTAGE CONTROL METHOD

Speed

(N) in

r.p.m

S.NOFrequency in Hz

f=PN/120SPEED IN RPM

(N)

MODEL GRAPH:

Frequency in Hz

Viva Questions:

1.What are the speed control methods of induction motor?2.Write the speed equation for induction motor?3.What are the speed control methods for Slip-ring Induction motor.4.Define Synchronous speed.

RESULT:

Em-II Manual Final

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