Electrical machines miscellaneous Easy Questions and Answers

Electrical machines miscellaneous

1. field current required to produce rated voltage on full load and field current required to produce rated current on SC.
1. field current required to produce rated voltage on OC and field current required to produce rated armature current on SC.
1. field current required to produce rated voltage on SC and field current required to produce rated current on SC.
1. field current required to produce rated voltage on full-load and field current required to produce rated voltage on SC.

The flux per pole in a synchronous motor with the field circuit ON and the startor disconnected from the supply is found to be 25 mWb. When startor is connected to the rated supply with the field excitation unchanged, the flux per pole in the machine is found to be 20 mWb while motor is running on no load. Assuming no load losses to be zero, the no load current drawn by the motor from the supply

1. lags the supply voltage
1. leads the supply voltage
1. is in phase with the supply voltage
1. is zero

1. difference of armature leakage reactance and reactance equivalent of armature reaction.
1. same as armature leakage reactance.
1. reactance equivalent of armature reaction.
1. sum of armature leak age reactance and reactance equivalent of armature reaction.

In a synchronous machine, the voltage induced by armature reaction flux acts like the voltage drop in

1. inductive reactance
1. resistance
1. capacitive reactance
1. inductive impedance

As observed from the startor of a synchronous generator, the armature reaction mmf phasor

1. lags behind the armature current phasor by 90°.
1. is in phase with the armature current phasor.
1. leads the armature current phasor by 90°
1. in phase opposition to the armature current phasor.