Electrical Machines-II TE Electrical

EXPERIMENT NO. 1 O. C. And S. C. Test on

AIM: Determination of regulation of cylindrical alternator by o.c. and s.c. test APPRATUS:

 Ammeter (0-5A) A.C,(0 – 2)A D. C.

 Voltmeter (0 – 600V) A. C.

 Alternator 3.5 KVA, 415V, 4.5A, 1500 rpm, 50Hz

 D.C. Motor 5 BHP, 220 V, 1500 rpm, 19A

 Rheostat - 2 750 ohm, 1.4A

 Tachometer 0 – 3000 rpm

 Multimeter

PROCEDURE:

 Connect the circuit as shown in the circuit diagram.  Make sure the rheostat in d c motor field is at minimum position and rheostat in alternator field is at maximum position.  Start D. C. Motor  Set the speed of d. C. Shunt motor to 1500 rpm by field rheostat of d. C. Motor.

For O.C. test

 Note down the voltmeter reading when switch in field of alternator is open. This is due to residual magnetism when field current is zero.

 Close the switch in field circuit (single pole), take down readings of D. C. Ammeter (If) and

A. C. Voltmeter (VOC) by gradually reducing resistance in the field circuit of alternator.

 Take down readings upto VOC = 440 V. Field current of alternator should not exceed its rating.  Increase resistance gradually, then directly switch off d. c. Supply.

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For S. C. Test

 Connect Ammeter in R and Y terminal of alternator, Short Y and B terminals  Make sure rheostat positions of both machine fields a.Motor field rheostat - minimum, b. Alternator field rheostat – maximum position.  Switch on D.C. supply, start d. C. Motor by 3 point .  Adjust speed of d.c. motor at 1500 rpm by field rheostat.  Close the single pole switch, d.c. ammeter will be at minimum reading.

 Take down d. C. Ammeter reading (If) and a.c. ammeter (ISC)reading by gradually reducing field resistance of alternator.  Short circuit current of alternator must be below 4.2A that is rated current of alternator.  Increase resistance to max of alternator field and switch off d.c. supply.  Remove connections.

OBSERVATION TABLE:

1. D. C. Resistance test Measure resistance across R and N of alternator

RDC = ...... ohm RAC = 1.2 * RDC = ...... ohm

2. O. C. Test

Sr. No. If amps VOC Volts

1 0

2

3

4

5

6

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3. S. C. Test

Sr. No. If amps ISC Volts

1

2

3

4

5

 CALCULATIONS:

Synchronous Impedance (EMF) method

1. Plot graph of OCC and SCC

2. From the graph of OCC, find If for rated voltage 400V.

3. For the same If, find SC current = ISC1 /√ 4. Calculate Synchronous Impedance = ohm 5. winding is star connected. 6. = − ohm. 7. = = √×

8. / = cos∅ + + sin∅ +

= Volts/ph.

Since we have to calculate regulation at full load, so, Vph is rated voltage / √3 and rated current is calculated from step 7.

9. Calculate % = / × 100

10. for leading p.f., IaXS is negative in above formula.

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Mmf method.

1. Draw mmf triangle as per procedure in theory.

2. Find Eg corresponding to IFR from graph of OCC. 3. Calculate % = × 100

 RESULT TABLE:

Power Regulation by Emf method Regulation by mmf method factor

0.8 lagg

0.8 lead

Unity

 CONCLUSION:

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EXPERIMENT NO. 2

Regulation of cylindrical rotor alternator by Potier triangle method

AIM: To study the regulation of Alternator by Potier Method.

APPRATUS:

 Ammeter (0-5 A) AC,( 0-2 A) DC

 Voltmeter (0-600V) AC.

 Alternator 3.5kVA, 415 V , 4.5A,1500rpm, 50 Hz.

 DC Motor 5HP, 220 V , 20A , 1500 rpm.

 Inductive load bank 3 ɸ star connected.

PROCEDURE:

 Connect the circuit as per the circuit diagram.  Make sure positions of field rheostat of motor and alternator.  Make sure load is at zero position.  Start d.c. shunt motor adjust its speed to 1500 rpm.  Increase voltage of alternator by field rheostat to slightly more than rated value i.e. 440 V.  Switch on load bank.  Adjust the load current to rated value nearly equal to 4 Amps.  Voltage will drop, for rated current, take down field current and terminal voltage of alternator.  increase field excitation, (keeping an eye on field current) also maintain full load current of alternator and take down correspondong load voltage readings.  Increase field current upto rated value and take voltage readings by maintaing load current constant. Reduce load to zero vale, simulaneously reduce voltage of alternator. 12. Switch off d.c. supply.

OBSERVATION TABLE:

Sr.No.

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Graph:-

1. Plot OCC from OC test

2. Plot ZPF curve i.e. If on X axis and VL on Y axis

3. Draw potier triangle as per theory and calculate regulation.

RESULT :- % regulation at zero p.f. lagging =

CONCLUSION:

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EXPERIMENT NO. 3 Direct loading test on alternator

AIM: To determine regulation of alternator by direct loading

APPRATUS:

 Voltmeter (0 – 600V) A. C.

 D. C. Motor coupled to Motor : 5 BHP, 220 V, 1500 alternator set rpm, 19A, with three point starter Alternator 3.5 KVA, 415V, 4.2A

 Rheostat – 2 750 ohm, 1.4A

 Tachometer 0 – 3000 rpm

 Ammeter (0-2)A d.c.

 Frequency meter Digital frequency meter.

 Ammeter - three (0 – 5A) A.C.

 Three phase lamp 415V, 10A, star connected bank

PROCEDURE:

 Connect the circuit as per the circuit diagram.  Keep the field rheostat of d.c. motor at minimum position and field rheostat of alternator at maximum position.  Switch on d.c. supply and start d.c. shunt motor.  Adjust the speed of d.c. motor to 1500 r.p.m. Adjust rheostat in field circuit of alternator such that it gives rated voltage i.e. 400V. Take down voltmeter reading. This is no load voltage of alternator.  Switch ON load suct that ammeter of each phase indicate same reading.  Check speed of motor, if it is reduced, adjust the speed to 1500 r.p.m. at this loading condition.  Take down readings of ammeter and voltmeter by gradually increasing load. At each loading condition, speed should be adjusted to 1500 rpm.  Switch off load bank.

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 Adjust rheostat of alternator field to maximum position and switch off d.c. supply.

OBSERVATION TABLE:

Sr. Ia amps VL (volts) N rpm No.

 CALCULATIONS:

√

% Regulation = × 100 =

VNL = Eg

Plot graph of V Vs IL.

 RESULT TABLE:

Sr. Ia % R No

CONCLUSION:

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EXPERIMENT NO. 4 Slip Test on alternator

AIM: Determination of regulation of salient pole alternator by slip test. APPRATUS:

 Ammeter (0-5A) A.C

 Voltmeter (0 – 600V) A. C. (0 – 100)A.C.

 Alternator 3.5 KVA, 415V, 4.5A, 1500 rpm, 50Hz

 D.C. Motor 5 BHP, 220 V, 1500 rpm, 19A

 Rheostat 750 ohm, 1.4A

 Tachometer 0 – 3000 rpm

 Ammeter (0-5A) A.C

PROCEDURE:

 Connect the circuit as per the circuit diagram.  Make sure rheostat in d c motor field circuit is at minimum position.  Switch On d. C. Supply and start d. C. Shunt motor.  Adjust speed of d.c. motor less than synchronous speed nearly equal to 1485 rpm.  Apply low three phase voltage through auro transformer to stator of alternator.  As rotor speed is near synchronous speed, stator voltmeter and ammeter indicate minimum and maximum values.  Note down these stator voltage and current minimum and maximum values.  Reduce a. c. Voltage to zero, switch off a.c. supply, switch off d.c. supply.  Remove connections.

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OBSERVATION TABLE:

Sr. Stator voltage Stator current Field Voltage No.

Vmax Vmin Imax Imin Vf min Vmax (Volts) (Volts) (Amps) (Amps) (volts) (volts)

1

 CALCULATIONS:

D. c. resistance of stator winding = RDC = 4 ohms, RAC = 1.2 * RAC = ...... ohms.

1. = ℎ 2. = ℎ 3. = = ...... Volts √ 4. = = ...... √× 5. cos∅ = 0.8 6. sin∅ = 0.6 7. tan = ∅ = ∅ 8. ∴ = 9. = −∅ =

10. = sin = 11. = cos =

12. = cos + + = 13. % Regulation = × 100 =

 RESULT TABLE:

Sr. No Xd Xq Egph % Regulation

 CONCLUSION:

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EXPERIMENT NO. 5 V and inverted V curve of

AIM: To plot variation of power factor and input current of a synchronous motor with respect to field current at constant load.

APPRATUS:

 Ammeter (0-5A) A.C , (0-2)A D.C.

 Voltmeter (0 – 600V) A. C.

 Alternator 3.5 KVA, 415V, 4.5A, 1500 rpm, 50Hz

 Synchronous Motor 5 BHP, 415 V, 50Hz, 1500 rpm, 4.5A

 Rheostat 750 ohm, 1.4A

 Tachometer 0 – 3000 rpm

 3 phase 0 – 450V, 3 phase. autotransformer

 Wattmeter (0 – 10)A, (0 – 600)V

 Single pole switch

PROCEDURE:

 Connect the circuit as per the circuit diagram.  Make sure rheostat in field circuit of synchronous motor is at mid position and switch is open.  Autotransformer variable pot should be at minimum position. Switch on 3 ph a.c. supply, increase input voltage gradually, check direction of rotation, motor is now started as .  Increase voltage upto 290V, check speed of motor.  If speed is beyond 1350 rpm, switch on d.c. supply, close the single pole switch.  Motor is now pulled into synchronism, increase input voltage by auto transformer upto 415V.

 Bring the rheostat to max. Position, take down readings of If, W1, W2, IL, VL by gradually increasing field current in steps.

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 When p. f. is low, motor acts at poor lagging power factor, so one of the wattmeter will give negative reading. In order to measure its readings current coil connections should be revered, i.e. M and L terminals connections should be interchanged.  When field current is increased, motor power factor will be unity and both wattmeters will give positive readings.  When field current is further increased, motor acts as leading power factor load. Again one of the wattmeter will give negative readings, so again M and L terminals of corresponding wattmeter has to be reversed.  For switching off of motor, first increase field resistance, switch off d.c. supply, reduce 3 phase a. c. Voltage to zero and then switch off a.c. supply, open the field circuit single pole switch.  Always follow correct procedure for switch on and switch off the motor.

OBSERVATION TABLE:

Sr. No. d.c. Field W1 W2 IL VL

current If Watts watts Amps Volts amps

1

2

3

4

5

6

 CALCULATIONS:

= ± = √3 cos∅ ∴ cos∅= √3

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 RESULT TABLE:

Sr. d.c. Field IL ∅

No current If Amps Lag, lead, amps unity

1

2

3

4

5

6

 CONCLUSION:

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EXPERIMENT NO. 6 Speed control of Induction motor by V/F method

AIM: To study speed control of 3 phase Induciton motor by varying frequency and maintaining V/F ratio constant.

APPRATUS:

 Voltmeter (0 – 600V) A. C.

 D. C. Motor coupled to Motor : 5 BHP, 220 V, 1500 alternator set rpm, 19A, Alternator 3.5 KVA, 415V, 4.2A

 Rheostat – 2 750 ohm, 1.4A

 Tachometer 0 – 3000 rpm

 3 phase Induction Motor 415V, 3 phase, delta connected.

 Frequency meter Digital frequency meter.

 Ammeter (0 – 2A) D.C.

 Voltmeter (0 – 600V) A. C.

 D. C. Motor coupled to Motor : 5 BHP, 220 V, 1500 alternator set rpm, 19A, Alternator 3.5 KVA, 415V, 4.2A

PROCEDURE:

 Connect the circuit as per the circuit diagram.  Keep the field rheostat of d.c. motor at minimum position and field rheostat of alternator at maximum position.  Switch on d.c. supply and start d.c. shunt motor  Adjust Field rheostat of alternator and field rheostat of motor such that v/f ratio is 8.  Take down readings of V, F, and speed of Induction Motor by increasing frequency in steps. Take 4 to 5 readings.  Reduce d.c. current of alternator i.e. increase rheostat of alternator, switch off d.c. supply.

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OBSERVATION TABLE:

Sr. No. V (Volts) F (Hz) N rpm

1

2

3

4

5

Graph:- Plot the graph of Frequency of alternator i.e. input frequency of Induction motor Vs. Speed of Induction Motor.

CONCLUSION:

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EXPERIMENT NO. 7

Load test on AC series motor

AIM: To perform Load test on AC series motor.

APPRATUS:

 Voltmeter (0 – 300V) A. C.

 A C series motor 1 HP, 230 V,1500 rpm, 6.8A

 Auto Transformer 0 – 260V, Single phase

 Tachometer 0 – 3000 rpm

 Wattmeter 0 – 10A, 300V

 Ammeter (0 – 10A) D.C.

 Voltmeter (0 – 300V) A. C.

 A C series motor 1 HP, 230 V,1500 rpm, 6.8A

 Auto Transformer 0 – 260V, Single phase

PROCEDURE:

 Connect the circuit as per the circuit diagram.  Make sure that there is some load on motor and auto transformer is at zero position.  Switch on a.c. supply and apply voltage gradually to motor.  Take down readings of weights M1, M2, W, V and I and speed N by applying full load to motor.  Gradually reduce load on the motor in steps and take down readings at each step.  Take precaution that speed of motor should not be too high.  Reduce voltage and switch off the motor.

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OBSERVATION TABLE:

Sr. No V volts I amps W watts N rpm M1 Kg M2 Kg

1

2

3

4

5

 CALCULATIONS:  Radius of the pulley = R = ……….m

 = − × 9.81 × = Nm.

 = = W /

 % = = %

 cos∅ = = ×

 RESULT TABLE:

Sr. No Output P I (amps) T (Nm) % ∅ (Watts)

1

2

3

4

5

CONCLUSION:

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EXPERIMENT NO. 8 Load test on single phase CSCR Induction motor

AIM: To perform Load test on single phase CSCR Induction motor

APPRATUS:

 Voltmeter (0 – 300V) A. C.

 Single phase CSCR 1 HP, 230 V,1500 rpm, 6.8A Induction Motor

 Auto Transformer 0 – 260V, Single phase

 Tachometer 0 – 3000 rpm

 Wattmeter 0 – 10A, 300V

 Ammeter (0 – 10A) D.C.

 Voltmeter (0 – 300V) A. C.

 Single phase CSCR 1 HP, 230 V,1500 rpm, 6.8A Induction Motor

 Auto Transformer 0 – 260V, Single phase

PROCEDURE:

 Connect the circuit as per the circuit diagram.  Make sure that there is no load on motor and auto transformer is at zero position.  Switch on a.c. supply and apply voltage gradually to Induction motor.  Take down no load readings of weights M1, M2, W, V and I and speed N.  Increase load on the motor in steps and take down readings at each step.  Reduce load and switch off the motor.

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OBSERVATION TABLE:

Sr. No V volts I amps W watts N rpm M1 Kg M2 Kg

1

2

3

4

5

 CALCULATIONS:  Radius of the pulley = R = ……….m

 = − × 9.81 × = Nm.

 = = W /

 % = = %

 cos∅ = = ×

Plot graph :- on x axis : output P and on y axis: N, T,cos∅, slip,% efficiency.

 RESULT TABLE:

Sr. Output P I (amps) T (Nm) % ∅ Slip No (Watts)

1

2

3

4

5

CONCLUSION:

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EXPERIMENT NO. 9 No load and blocked rotor test on CSCR Induction motor

AIM: To perform no load and blocked rotor test on capacitor start, capacitor run Induction motor.

APPRATUS:

 Voltmeter (0 – 300V) A. C.

 Single phase CSCR 1 HP, 230 V,1500 rpm, 6.8A motor

 Auto Transformer 0 – 260V, Single phase

 Tachometer 0 – 3000 rpm

 Wattmeter 0 – 10A, 300V

 Ammeter (0 – 10A) D.C.

PROCEDURE:

a. No load test  Connect the circuit as per circuit diagram.  Single pole switch between A2 and M2 should be closed.  Apply voltage gradually by autotransformer.  Once the voltage is applied to rated value 230V, open the switch.  Take down no load readings of voltage, current and power and speed.  Reduce voltage to zero by auto transformer.  Switch off supply.

b. Blocked rotor test  Keep single pole switch open and apply voltage gradually.  Voltage must be applied very carefully such that ammeter must show rated current i.e. 6.8A.  Take down wattmeter, voltmeter and ammeter readings.  Reduce voltage to zero and switch off the supply.

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OBSERVATION TABLE:

No load test

Sr. No V0 volts I0 amps W0 watts N rpm

Blocked rotor test

Sr. No VBR volts IBR amps WBR watts

 CALCULATIONS:

From blocked rotor test,

 = +

 ∴ + = =

 R1AC = 1.2 × R1DC. =

 R2’ = (R1 + R2’) – R1 =

 = + = − + =

 Assume X1 = X2’ hence X1 = X2’ = X/2

From no load test,

 cos∅0 = =

 = =

 = 1− cos∅0

 = + +

 Calculate X0 from above formula.

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 RESULT TABLE:

Sr. No R1 ohm X1 ohm R2’ ohm X2’ ohm X0 ohm

CONCLUSION:

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EXPERIMENT NO. 10 Synchronisation of Alternator (one dark and two equally bright lamp method)

AIM: To study synchronisation of incoming three phase alternator with bus bar using one dark and two bright lamp method.

APPRATUS:

 Voltmeter – 2 (0 – 600V) A. C.

 D. C. Motor coupled to Motor : 5 BHP, 220 V, 1500 alternator set rpm, 19A, with three point starter Alternator 3.5 KVA, 415V, 4.2A

 Rheostat – 2 750 ohm, 1.4A

 Tachometer 0 – 3000 rpm

 Frequency meter Digital frequency meter.

 Bus bar terminals 3 phase, 4 wire connections

 Phase sequence meter 3 phase

 Lamp bank panel with DPDT switch and terminals

CIRCUIT DIAGRAM:

PROCEDURE:

 Connect the alternator and d.c. motor circuit as shown in the circuit diagram  Take down readings of MSEB supply voltage, phase sequence and frequency.  Start d.c. shunt motor and adjust its frequency and supply voltage and phase sequence equal to MSEB values. Switch off d.c. motor.  Connect one side of lamp bank panel to MSEB supply and another side to alternator terminals. Connect voltmeter between R and Y of alternator and MSEB.  Now start d.c. shunt motor and adjust frequency and voltage of alternator equal to MSEB values.  Start MSEB supply.

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 You can see lights getting dark and bright simultaneously.  Adjust frequency and voltage such that one lamp becomes dark and other two equally bright for longer time. When Lamp in R phase is dark and lamps in Y and B phase are equally bright, this is the time of synchronisation. Do not close DPDT switch in any case.  Switch off MSEB and reduce voltage of alternator and switch off d.c. motor.

OBSERVATION TABLE:

Bus bar parameters

Incoming alternator parameters:-

Phasor diagram

CONCLUSION:

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