ECE 420 Experiment No. 1

Spring 2011 – on-campus Synchronous Generator Parameters

Experiment No. 1

Synchronous Generator Parameters

Objectives

The objectives of this experiment are to find the direct-axis reactance (Xd)and quadrature-axis reactance (Xq) and mutual reactance including saturation from open circuit characteristic and loading of a 3-  synchronous generator.

Apparatus

  1. 2 test tables
  2. DC motor-synchronous generator set
  3. 1  field rheostat
  4. 1 5 A Kenwood DC power supply
  5. 1 0-5 A DC ammeter
  6. 1 0-10 A DC ammeter
  7. 1 0-150 VDC voltmeter
  8. 1 current transformer
  9. 1 0-5 A AC ammeter
  10. 2 Wattmeters
  11. 1 0-300/150 V AC voltmeter
  12. Tachometer for synchronous generator
  13. Strobe

Procedure

Part 1: Open Circuit Characteristic (OCC)

a)Set up the circuit shown in Fig.1. The synchronous generator should be connected for 220 V 3- wye operation.

b)Start the DC motor.

c)Adjust IFmotor until the speed of the dc motor-synchronous generator set, n, is at synchronous speed; i.e., n= ns.

d)Holding the speed constant, adjust IFgen until VOC equals 140% of rated voltage. Measure and record IFgen, VOC and n.

e)Turn off the motor-generator set.

Part 2: Reactive Loading of Synchronous Generator

a)Set up the circuit shown in Fig.2. The synchronous generator should be connected for 220 V 3-  wye operation.

b)Keep the switches of test table 2 open. Start the DC motor.

c)Adjust IFmotor until the speed of the dc motor-synchronous generator set, n, is at synchronous speed; i.e., n= ns.

d)Adjust IFgen until the voltage across the terminals of synchronous generator is brought to rated value. Measure IFgen.

e)Make sure that the capacitive bank is connected to the rated voltage. Initially, set the capacitive bank to infinity.

f)Close the switches of test table 2 and adjust the load to 20A approximately. Measure the currents (I1, I2, and I3) and voltages (V12, V23, and V31) at the terminals of the source.

g)Repeat part f for different load conditions. Make sure the load is balanced.

h)Turn off the motor-generator set.

Part 3: Real Loading of Synchronous Generator

a)Set-up and synchronize the synchronous generator to Avista per Experiment 2 instructions. The synchronous generator should be connected for 220 V 3-  wye operation.

b)Decrease IFmotor until the synchronous generator armature current is approximately 10 amperes. This operating condition result in Iad equal to approximately zero.

c)Measure IFgen, the currents (I1, I2, and I3) and voltages (V12, V23, and V31) at the terminals of the synchronous generator.

i)Turn off the motor-generator set.

Report

  1. Plot the open circuit characteristic voltage, VLN, versus If using the data from Part 1.Determine the average slope of the initial open circuit voltage versus field currentline using the equation given below which will yield theunsaturated value of the stator fieldmutual inductance Xsfu.

Where VOC0 is the voltage due to the residual flux andIf = IFgen/(sqrt(2))

  1. Plot the airgap line on the same graph. The air-gap line is a plot of Easu versus field current, If.
  1. Calculate XI and KI using the last two data points from Part 1; i.e. the data points for which the field current yields Easu equal to 1 pu and 1.2 pu.
  1. Using the data from Part 2 of the experiment, calculate Xd (average the two values you calculate) using the following equation

Where Eas is the induced emf

Vatsis the measured terminal voltage of the synchronous machine

Xd is the direct axis reactance

Xq is the quadrature axis reactance

Ias is the stator line current in phase A.

Iad is the direct axis stator current

Iaq is the quadrature axis stator current.

Note that Iaq = zero for Part 2.

  1. Using the data from Part 3 of the experiment, calculate Xq (average the two values you calculate) using the following equation

Assume that Iad = zero for Part 3.

Part 1: Tabular Form for Open Circuit Characteristic (OCC):

S.No / IFgen
A / V12
V / V23
V / V31

V

/
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.

Part 2: Tabular Form for Reactive Loading:

S.No / I1

A

/ I2
A / I3
A / IL

A

/ V12
V / V23
V / V31
V / VT
V / IFgen
A / VFgen
V / IFmotor
A / NS
RPM
1.
2.
3.
4.

Part3: Tabular Form for Reactive Loading:

S.No / I1

A

/ I2
A / I3
A / IL

A

/ V12
V / V23
V / V31
V / VT
V / IFgen
A / VFgen
V / IFmotor
A / NS
RPM
1.
2.
3.
4.
5.
6.

Where

NS = Synchronous speed

Fig. 1: Circuit diagram of the laboratory setup for determining the open circuit characteristics

Fig. 2: Circuit diagram of the laboratory setup for reactive loading.

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