Single Phase Motors
In a universal motor, the most common cause of brush sparking is

high commutator mica
shorted field winding?
open armature winding
all of these

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Single Phase Motors
Which of the following statements regarding a reluctance motor is incorrect ?

It cannot be reversed, ordinarily
Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluc-tance path between stator and rotor
It is nothing else but a single-phase, salient pole synchronous-induction motor
It requires no D.C. field excitation for its operation

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Single Phase Motors
Hysteresis motor is particularly useful for high-quality record players and tape-recorders because

it revolves synchronously
it is not subject to any magnetic or mechanical vibrations
it can be easily manufactured in extremely small sizes of up to 1 W output
it develops hysteresis torque which is extremely steady both in amplitude and phase

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