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DDWK 3711 Electrical Machine

Experiments 2 : Three-phase Synchronous Generator

Update : May 2018 NDM

JABATAN KEJURUTERAAN ELEKTRIK PUSAT PENGAJIAN DIPLOMA (PPD), SPACE

UNIVERSITI TEKNOLOGI MALAYSIA KUALA LUMPUR

DDWK 3711

(ELECTRICAL MACHINE)

EXPERIMENT 2

THREE-PHASE SYNCHRONOUS GENERATOR

Sekolah Pendidikan Profesional dan Pendidikan Berterusan (SPACE)




Part 1: Measurement of the windings resistance

Objective ;

To calculate the winding resistance of asynchronous motor and generator with the Volt-Ampere

method (Ohm’s Law).

Theory ;

The motor windings resistance cause internal voltage drops that reduce their efficiency. Therefore

it must be as low as possible. It is calculated by applying DC voltages and measuring the resulting

current flows.

Formula:

PARAMETER SYMBOL UNIT

Winding Voltage V Volts

Winding Current I Amperes

Winding resistance R

For a star phase connection: R = V / 2 * I

Figure 1: Diagram of Synchronous Machine

V

A

PS3




1. Execution

The components must be connected as shown in the circuit diagrams and must be grounded.

MANUAL DATA COLLECTION AND ANALYSIS

1. Set the DC windings voltage PS3 = 0 V.

2. Switch on the power supply. Increase PS3 gradually by operating on the front knob.

It must be increased in 2% steps up to 10% max.

Do not exceed 10% of nominal winding voltage to avoid excessive winding

temperature.

3. Measure the voltage and current for any step and enter them in the experiment

report table 1.

4. Repeat the above steps for all windings of all phases and calculate their resistance

with the formula given above.

5. Now calculate the average value of the resistance for each phase winding. They

should be similar.

Execution Diagram :




Part 2 : No Load Test

This experiment is performed on a SynchronousMachine.

Objective :

Plot the magnetization characteristics of a synchronous generator.

Theoretical review :

This experiment shows the characteristics of electromotive force Eo against the excitation/field

current Ie. The resulting graph shows that for the same value of excitation current there are two

different values of electromotive eforce, one for the ascendingand one for th descending curves.

Usually the medium value of Eo is considered.

The area enclosed in the magnetization loop represents the power losses for magnetic hysterisis

(residual magnetism)in the armature iron.

Formula :


Voltage E01 Volts

ExcitationCurrent Ie Amperes

Pair of Poles p

Speed n1 rpm

Frequency F1 Hz

Theoretical Frequency f Hz

Theoretical Speed n rpm

Theoretical Voltage Eo Volts

Eo/Eo1 = n/n1

Eo = Eo1 * (n/n1) = Eo * (f/F1)

n = (60 * f)/p




Components :

Three Phase SynchronousMachine Model A4223

Squirrel Cage Three Phase Drive Motor Model A4220

Power Supply Model A0240

Paralleling Board Model A481 0

Cables Model A4890

Cables support Model A4891

Coupling Base Model A4840

Tachometer Model A4725

Ammeter With adequate range for this test

Voltmeter With adequate range for this tes

Frequency meter (F) Optional

CIRCUIT DIAGRAMS :

Theoretical Diagram :




Execution Diagram :

2. Exercusion :

The components must be connected as shown in the circuit diagrams and must be grounded. The

Synchronous machine is mechanically coupled to the driving asynchronous motor.




Manual Data Collection And Analysis :

1. Set the excitation voltage PS4 and drive motor voltage PS1=O.

2. Switch on the power supply and adjust Psi to nominal motor voltage (400 V). When

the motor is up to speed gradually increase the excitation voltage from 20 V to 120 V

in 10 V steps (shown in Table2 in the report sheet).

3. At each step enter in the worksheet Table 2 the values of the excitation current Ie,

Voltage E01 and frequency F1.

4. Plot the graph of voltage Eo, versus excitation current Ie. Maximum Ie = 0.2 A.

Part 3 : Short Circuit Test

This experiment is performed on a Synchronous Machine.

Objective :

Plot the short circuit characteristics of a synchronous generator. The short circuit diagram shows

the output current versus the excitation current when the armature windings are short circuited.

Theory :

This test is performed by driving the generator to a speed close to nominal and by measuring the

Short circuit current while stepping up the excitation current. It is not necessary to measure the

output frequency as the short circuit current is largely independent from speed when the qenerator

is running close to nominal RPM.




Measurement :


Excitation Current A1 Amperes

Current 1 A2 Amperes



Short Circuit Current Isc Amperes

Components :

Three Phase Synchronous Machine Model A4223

Squirrel Cage Three Phase Drive Motor Model A4220

Power Supply Model A0240

Cables Model A4890

Cables support Model A4891

Coupling Base Model A4840

Ammeter (A1, A2, A3, A4) With adequate range for this test

Circuit Diagram :

Theoretical Diagram :




Exercution Diagram:

3. Exercusion :

The components must be connected as shown in the circuit diagrams and must be grounded. The

Synchronous machine is mechanically coupled to the driving asynchronous motor.




Manual Data Collection and Analysis :

1. Set the excitation voltage PS4 and motor supply voltage PS1=O.

2. Switch on the power supply. Start the driving motor.

3. When the motor reaches nominal speed, step up the excitation current Ie until

nominal current is reached.

4. At each step enter in Table 3 in the report sheet the values of the excitation and

generator currents.

5. Calculate the short circuit current as the average of the generator currents.

6. Plot the graph lsc versus Ie.

Maximum lsc = 1.3 A

Maximum Ie,= 0.2 A

Notes: Since the short circuit test is linear, it can be drawn by measuring only two points.


Report Sheet 1 Three Phase Transformer

Update: May 2018 NDM Page 1

JABATAN KEJURUTERAAN ELEKTRIK PUSAT PENGAJIAN DIPLOMA (PPD), SPACE

UNIVERSITI TEKNOLOGI MALAYSIA KUALA LUMPUR

DDWK 3711 (ELECTRICAL MACHINE)

REPORT SHEET

EXPERIMENT 2: THREE PHASE SYNCHRONOUS GENERATOR

Group members 1.

2.

3.

4.

5.

Lecturer :

Date :

No. PLO CLO Student Marks Marks

1 PLO1 CLO6 40

2 PLO2 CLO6 50

3 PLO8 CLO6 10

Total Marks /100

UTM

UNIVERSITI

TEKNOLOGI MALAYSIA

Sekolah Pendidikan Profesional dan Pendidikan Berterusan (SPACE)




Part 1 : Measurement of the windings resistance

Phase Parameter Parameter

Value

Rdc = Vdc/Idc (Ω) Ra = ⅟ 2 Rdc (Ω)

UW Vdc RdcUW = RaUW =

Idc

WV Vdc RdcWV = RaWV =

Idc

VU Vdc RdcVU = RaVU =

Idc

Table 1

Average winding resistance, Ra = (RaUW + RaWV + RaVU)/3 = ______________ Ω

Machine model : _____________________________

Rotor/stator : _______________________________

PLO1 CLO6 ………

/10m




Part 2 : No Load Test

Parameter Symbol Unit Value

Excitation current Ie A

Voltage Eo1 V

Frequency F1 Hz



Voltage Eo1 V

Frequency F1 Hz

Table 2

Machine model : ___________________

PLO1 CLO6 ………

/10m

Part 3 : Short Circuit Test



Short Circuit

Current Isc A



Short Circuit

Current Isc A

Table 3

PLO1 CLO6 ………

/10m




Answer the following Questions

Q1. List the ratings of power, voltage and current of the synchronous generator and the induction

motor from the name plate mounted on each machine.

…………………………………………………………………………………………………

…………………………………………………………………………………………………

…………………………………………………………………………………………………

…………………………………………………………………………………………………

PLO1 CLO6 ………

/5m

Q2. State the purpose of coupling induction motor to the synchronous generator.

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

PLO1 CLO6 ………

/2m

Q3. Discuss the significance of performing the,open circuit and short circuit tests on the

synchronous generator.

…………………………………………………………………………………………………

…………………………………………………………………………………………………

…………………………………………………………………………………………………

…………………………………………………………………………………………………




…………………………………………………………………………………………………

…………………………………………………………………………………………………

…………………………………………………………………………………………………

PLO1 CLO6 ………

/6m

Q4. From the experiment data, plot the graphs of Voc vs Ie, and Isc vs le on the same axis, showing

the open circuit and short circuit characteristics. Give comments on the graphs obtained.

…………………………………………………………………………………………………

….………………………………………………………………………………………………

…………………………………………………………………………………………………

…………………………………………………………………………………………………

PLO1 CLO6 ………

/12m

Q5. From the two graphs, plot a graph of synchronous impedance, Zs and determine the value of

Zs at rated voltage of the synchronous generator. Then, calculate the synchronous reactance

Xs, at this voltage.

PLO1 CLO6 ………

/15m




Q6. Write the conclusion of the experiment.

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

PLO1 CLO6 ………

/10m

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