MCQs on Electrical Machines

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01․ The frame of an induction motor is made of
closed grained cast iron.
silicon steel.
stainless steel.
aluminium.

Under construction.
02․ Use of fractional pitch winding
make it stiffer.
results in reduced leakage reactance.
results in reduced axial length of the machine.
all of the above.

Under construction.
03․ The stator core of a 3 - Φ induction motor is laminated in order to reduce the
hysteresis loss.
eddy current loss.
both of the above.
weight of the stator.

Under construction.
04․ In a three phase slip-ring induction motor, brushes are connected to
DC supply.
3 - Φ AC supply.
external star-connected resistors.
equalizing coils.

Under construction.
05․ The rotor winding for a 3-phase slip-ring induction motor having delta-connected stator must be connected in
delta.
star.
delta or star according to need.
none of the above.

Under construction.
06․ The squirrel cage induction motors are provided with blades in order to
eliminate noise.
balance the rotor dynamically.
facilitate cooling of rotor.
none of these.

Under construction.
07․ Induction motors normally use cast aluminium rotor because aluminium is
cheaper in cost.
lighter in weight.
of low resistivity.
easy to cast owing to its low melting point and is easily available.

Under construction.
08․ The shaft of induction motor should be
stiff.
hollow.
flexible.
any of these.

Under construction.
09․ The rotor of a 3 - Φ wound induction motor is provided with
heavy short-circuited end rings.
heavy copper or aluminium bars placed in rotor slots.
three phase winding.
single phase winding.

Under construction.
10․ In a 3 - Φ wound rotor induction motor the short circuit gear is used to short circuit the
rotor at slip rings.
stator phases of the motor.
starting resistance in the starter.
none of the above.

Under construction.
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