ISRO Scientist or Engineer Electrical 2015

Synchronous motor

Induction motor

Synchronous generator

Induction generator

Ratio of turns between primary and secondary windings

Frequency

Flux density in core

Angle between magnetic axis of the primary and secondary windings

The field winding must be excited by double the rated DC voltage

The armature connection must be reversed

The field winding connection must be reversed

Field winding must be excited by low voltage DC supply

Their speeds are identical

Their speeds and excitation are identical

Their speeds are equal and back emfs are half of the supply voltage

Their excitations are equal and back emfs are half of the supply voltage

Generator and operating at lagging pf

Generator and operating at leading pf

Motor and operating at a leading pf

Motor and operating at a lagging pf

Both $$\delta$$ and $$\phi$$ decreases

$$\delta$$ and $$\phi$$ both increases

$$\delta$$ increases but $$\phi$$ decreases

$$\delta$$ decreases but $$\phi$$ increases

$$3^{rd}$$ Harmonics

$$7^{th}$$ Harmonics

$$2^{nd}$$ Harmonics

$$5^{th}$$ Harmonics

The no-load pf of Motor A will be better than that of Motor B

The no-load pf of Motor A will be poorer than that of Motor B

The core losses of Motor A will be more than those of Motor B

The operating flux of Motor A will be smaller than that of Motor B

Positive and negative

Positive and positive

Negative and negative

Negative and positive

Mostly active

Mostly reactive

Active only

Active and reactive both