AC Machines — Summer 2022

Explain torque-slip characteristic of three-phase induction motor.

Derive EMF equation of alternator. Define coil span factor and distribution factor.

Why single-phase motor is not self-starting? explain the double field revolving theory in relation to single phase AC motors.

Explain production of rotating magnetic field in poly-phase induction motor.

Explain the phenomena of crawling in case of three-phase induction motor with its remedies.

State and explain any two method of speed control of Induction motor.

Explain the procedure to construct the circle diagram of induction motor. Also describe the method to determine losses, efficiency and slip at full load condition using circle diagram.

How does a synchronous motor differ from a three-phase induction motor?

Derive the relation between torque and voltage in case of three-phase induction motor.

Mention different starters for three phase induction motor and explain Star-Delta starter in details.

What conditions should be met while connecting an alternator in parallel with running paralleled alternators?

Describe the effect of armature reaction in case of an alternator.

Draw power stage diagram of three-phase induction motor. Show that in an induction motor the rotor input: power developed: rotor copper losses = 1: (1 - S): S, where S = fractional slip.

Draw the schematic diagram and explain the principle of induction generator.

How direct axis and quadrature axis reactance can be measured for salient pole machine?

List the methods of determination of voltage regulation of an alternator. Describe any one of them in detail.

What could be the reasons if a 3-phase synchronous motor fails to start?

Briefly explain V-curves of synchronous motor.1

Briefly explain that in case of double cage induction motor, torque and efficiency are higher as compared to normal squirrel cage induction motor during starting and running period respectively.

What is Hunting of Synchronous machine and how it prevents?

What is short circuit ratio of synchronous machine and how it’s effect to machine performance.

Draw the schematic diagram and explain the construction and working of shaded pole single phase motor.

What do you mean by Synchronous Condenser and how it’s different than Synchronous motor?

What is synchronization? Explain two bright one dark lamp method of Synchronization.

Explain the construction and working principle of Schrage motor.