ONLINE Multiple Choice Questions EE-Synchronous Motors PART 1


1. Synchronous
motor can operate at
(A) Lagging power factor only
(B) Leading power factor only
(C) Unity power factor only
(D) Lagging, leading and unity power factor
only.

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2. An
unexcited single phase synchronous motor is
(A) reluctance motor
(B) repulsion motor
(C) universal motor
(D) AC series motor.

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3. The
maximum power developed in the synchronous motor will depend on
(A) rotor excitation only
(B) maximum value of coupling angle
(C) supply voltage only
(D) rotor excitation supply voltage and maximum value of coupling angle.

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4. In
case the field of a synchronous motor is under excited, the power factor will
be
(A) leading
(B)
lagging
(C) zero
(D)
unity.

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5. A
synchronous motor is switched on to supply with its field windings shorted on
themselves. It will
(A) not start
(B) start and continue to run as an induction motor
(C) start as an induction motor and then run
as synchronous motor
(D)
bum immediately.

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6. When
the excitation of an unloaded salient pole synchronous motor gets disconnected
(A)
the
motor will bum
(B) the motor will stop
(C) the motor will ran as a reluctance motor
at the same speed
(D) the motor will run as a reluctance motor
at a lower speed.

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7. The
damping winding in a synchronous motor is generally used
(A) to provide starting torque only
(B)
to
reduce noise level
(C)
to
reduce eddy currents
(D)
to
prevent hunting and provide the starting torque.

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8. The
back emf set up in the stator of a synchronous motor will depend on
(A)
rotor
speed only
(B)
rotor
excitation only
(C)
rotor
excitation and rotor speed
(D)
coupling
angle, rotor speed and excitation.

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9. A
synchronous motor is a useful industrial machine on account of which of the
following reasons ?
I.
It
improves the power factor of the complete installation
II.
Its
speed is constant at all loads, provided mains frequency remains constant
III.
It
can always be adjusted to operate at unity power factor for optimum efficiency
and economy.
(A) I
only
(B) II only
(C)
III only
(D) I, II and
III.

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10. Which
of the following is an unexcited single phase synchronous motor ?
(A)
A.C.
series motor
(B) Universal motor
(C) Reluctance motor
(D) Repulsion motor.

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11. An
over excited synchronous motor draws current at
(A)
lagging
power factor
(B) leading power factor
(C) unity power factor
(D) depends on the nature of load.

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12. With
the increase in the excitation current of synchronous motor the power factor of the motor will
(A) improve
(B) decrease
(C) remain constant
(D) depend on other
factors.

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13. The armature current of a
synchronous motor has large values for
(A) low excitation
only
(B) high excitation only
(C) both low and high excitation
(D) depends on other factors.

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14. A synchronous motor is
switched on to supply with its field windings shorted on themselves. It will
(A) not start
(B) start and continue to run as an induction motor
(C) start as induction motor and then run as a synchronous motor.

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15. If the field of a
synchronous motor is under excited, the power factor will be
(A)
lagging
(B) leading
(C) unity.

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ONLINE Multiple Choice Questions EE-Synchronous Motors PART 2
ONLINE Multiple Choice Questions - Electric Machine Design PART 15

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