MCQs on Electrical Machines

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01․ Number of tappings for each equalizer ring is equal to
number of poles.
number of pole pairs.
number of commutator segments.
number of parallel paths.

Under construction.
02․ The terminal voltage of a DC shunt generator drops on load because of all of the following reasons except
commutation.
armature reaction.
armature resistance drop.
field weakening due to armature reaction.

Under construction.
03․ In a DC generator sparking between brushes and commutator surface may be due to
under commutation.
over commutation.
too rapid reversal of current.
any of the above.

Under construction.
04․ The change in speed of a DC generator due to increased load is corrected by
increasing input power of the prime mover.
increasing armature cooling.
increasing armature resistance.
increasing terminal voltage.

Under construction.
05․ Under commutation results in
no sparking.
sparking the trailing edge of the brush.
sparking at the middle of the brush.
sparking at the leading edge of the brush.

Under construction.
06․ In a DC shunt generator working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will
improve and terminal voltage will rise .
improve but terminal voltage will fall.
worsen and terminal voltage will rise.
worsen and terminal voltage will fall

Under construction.
07․ Commutation in a DC machine may be explained as a process
how alternate flux affects the main field flux.
by virtue of which emf is induced in the armature conductors.
by which electric current in a coil is reversed.
in which magnetic field is set up.

Under construction.
08․ Current in a coil undergoing commutation is not able to get reversed completely by the end of commutation period. It is due to
coil resistance.
armature emf.
reactance voltage induced in the coil.
none of the above.

Under construction.
09․ The self induced emf in the coil undergoing commutation is called the
statically induced voltage.
reactance voltage.
dynamically induced voltage.
none of the above.

Under construction.
10․ Sparkless commutation can be achieved by employing
inter poles.
compensating winding.
high resistance carbon brushes.
any one or more of the above methods.

Under Construction
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