UNIT 1 (Test 2)

What is the angle between stator direct axis and quadrature axis

• 90°

• 0°

• 45°

• 60°

Synchronous motor can operate at

• Lagging power factor only

• Leading power factor only

• Unity power factor only

• Lagging, leading and unity power factor only

The variation of reluctance Rl with space angle θr depends on the shape of

• stator poles

• rotor poles

• stator or rotor poles

• both stator and rotor poles

The maximum power developed in the synchronous motor will depend on

• rotor excitation only

• maximum value of coupling angle

• supply voltage only

• rotor excitation supply voltage and maximum value of coupling angle.

The single phase reluctance machine acts as a generator when angle δ is

• positive

• negative

• zero

• any of the mentioned

A synchronous motor is switched on to supply with its field windings shorted on themselves. It will

• not start

• start and continue to run as an induction motor

• start as an induction motor and then run as synchronous motor

• bum immediately

The damping winding in a synchronous motor is generally used

• to provide starting torque only

• to reduce noise level

• to reduce eddy currents

• to prevent hunting and provide the starting torque.

The back emf set up in the stator of a synchronous motor will depend on

• rotor speed only

• rotor excitation only

• rotor excitation and rotor speed

• coupling angle, rotor speed and excitation.

Which of the following is an unexcited single phase synchronous motor

• A.C. series motor

• Universal motor

• Reluctance motor

• Repulsion motor.

If the field of a synchronous motor is under excited, the power factor will be

• lagging

• leading

• unity.