ELECTRICIAN

ELECTRICIAN

A 3-phase synchronous motor connected to
AC mains is running at full load and unity
power factor. If its shaft load is reduced by half,
with field current held constant, its new
power factor will be.........
(a) Unity
(b) Leading
(c) Lagging
(d) Dependent upon motor parameters
Answer: (b) Leading
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The starting torque of slip-ring induction motor
can be increased by inserting a suitable ……..
in series with the rotor circuit of the motor,
(a) Capacitor
(b) Resistance
(c) Inductor
(d) Overload relay
Answer: (b) Resistance

The Growler instrument is made in ...............
type of iron core.
(a)  E & I
(b) Shell
(c) T&U
(d) H
Answer: (d) H

The voltage regulation of an alternator with power
factor of 0.8 lagging is ……. at unity power factor.
 (a) Greater than
(b) The same as
(c) Smaller than
(d) 100%
Answer: (a) Greater than
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A ceiling fan uses.......
(a) Capacitor start motor
(b) Universal motor
(c) Capacitor start and capacitor run motor   
(d) Split-phase motor
Answer: (a) Capacitor start motor

The voltage regulation of an alternator is larger
than that of a DC generator because of ..................
(a) Large armature resistance
(b) Large leakage reactance
(c) Complex effects of armature reaction
(d) Small armature resistance
Answer: (c) Complex effects of armature reaction

[f the excitation an alternator operating in
parallel with other alternators, is increased
above the normal value of excitation, its .........
(a) Output current decreases
(b) Power factor becomes more lagging
(c) Power factor becomes more leading
(d) Output KW decreases
Answer: (b) Power factor becomes more lagging