032/2020

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A two winding transformer operates at maximum efficiency when its
A) Hysteresis loss equal eddy current loss

B) Voltage regulation is minimum

C) Copper loss equals iron loss

D) Primary resistance equals secondary resistance

The transformer that does not provide electric isolation is
A) Power transformer B) Potential transformer
C) Current transformer D) Auto transformer

The synchronous speed of a three phase induction motor having 20 poles and
connected to a 50 Hz source is

A) 300 r.p.m. B) 600 r.p.m. C) 1000 r.p.m. D) 1200 r.p.m.

In a squirrel cage induction motor, the maximum torque developed under running
condition is

A) Equal to starting torque B) Full-load torque

C) Much higher than full load torque D) Less than starting torque

The purpose of starting winding in a single phase induction motor is to
A) Produce rotating flux in conjunction with main winding

B) Reduce losses

C) Limit temperature rise of the machine

D) None of the above

The stator of an alternator is identical to that of a

A) d.c. generator B) three phase induction motor
C) single phase induction motor D) none of the above
An under excited alternator supplies
A) Lagging VAR B) No reactive power
C) Leading VAR D) None of the above
Damper windings are used in alternators to
A) Prevent hunting B) Reduce winding losses
C) Achieve synchronism D) None of the above
A resistance split phase induction motor is used for
A) High inertial loads B) Low inertial loads
C) Very high inertial loads D) None of the above
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