Electromechanical Energy Conversion Experiment Report: Synchronous Motor V-Curves

THE HONG KONG POLYTECHNIC UNIVERSITY

DEPARTMENT OF ELECTRICLA ENGINEERING

2007-2008 SEMESTER 1

EE3021 Electromechanical Energy Conversion

Experiment Report: Synchronous Motor V-curves

Wang Kai

05945414D

2007-11-25

Objectives:

To draw the V-curves for a synchronous motor relating

(i) Excitation and stator current; (ii) Excitation and power factor.

Equipments:

2 kVA Motor-generator set from ASEA

Synchronous board

Power factor meter (5A, single-phase)

2:1 ratio current transformer

m.i. ammeter, 0/10A

m.c. ammeter, 0/2A

Theory:

The experiment adopted the rotary lamp method to perform synchronizing, as illustrated in Figure 1. The synchronizing switch can be closed when lamp L3 is dark and lamps L1 and L2 are equally bright.

With the switch open, the synchronous machine is started up and the speed is adjusted to a value close to synchronous speed. Field excitation is applied so that the machine voltage is approximately equal to the bus bar voltage.

The switch S should be closed when the bus bar voltage phasors and the machine voltage phasor coincide. Under this condition voltage across lamp L3 would be zero and voltages for lamp L1 and L2 are the same. This is the ideal instant for closing the switch.

Procedures:

1. Apply the rotary method to synchronize the motor.

2. Vary the excitation of the synchronous motor to change the power factor and the stator current. Take the readings of the stator current, excitation, power factor and torque over the stator current range of 6A to a minimum and then to 6A.

3. Restart the drive motor as generator with armature resistance at maximum and field current at minimum.

4. Adjust the D.C. generator field to load the synchronous motor. Choose the load to make the minimum of stator current be approximately 3A and repeat step 2.

5. Choose another load to let the minimum of stator...