Multiple Choice Questions on Electrical Machines - 2
Important Multiple
Choice Questions in Electrical Machines
1.
In a shaded pole induction motor, the rotor runs
from the
A)
Shaded portion to the unshaded portion of the
pole while the flux in the former leads that of the latter
B)
Shaded portion to the unshaded portion of the
pole while the flux in the former lags that in the latter
C)
Unshaded portion to the
shaded portion while the flux in the former leads that it in the latter
D)
Unshaded portion to the shaded portion while the flux in the former lags that in the
latter
2.
The torque of a reluctance motor can be
effectively increased by
A)
Increasing reluctance of the magnetic circuit
along the direct axis
B)
Decreasing the reluctance of the magnetic
circuit along the quadrature axis
C)
Increasing the ratio of
the quadrature axis reluctance to direct axis reluctance
D)
Decreasing the ratio of quadrature axis
reluctance to direct axis reluctance
3.
The starting current of a three phase induction
motor is 5 times the rated current, while the rated slip is 4%. The ratio of
starting torque to full-load torque is
A)
0.6
B)
0.8
C)
1.0
D)
1.2
4.
A single-phase transformer when supplied from
220V, 50Hz has eddy current loss of 50W. if the transformer is connected to a
voltage of 330V, 50Hz, the eddy current loss will be
A)
168.75W
B)
112.5W
C)
75W
D)
50W
5.
In case of auto transformer, which of the
following statements are correct?
I.
An auto-transformer requires less copper as
compared to a conventional 2-winding transformer of the same capacity
II.
An auto-transformer provides isolation between
the primary and secondary windings
III.
An auto-transformer has less leakage reactance
as compared to the conventional 2-winding transformer of same capacity
Select the correct answer using the codes given below
A)
1,2 and 3
B)
1 and 2
C)
1 and 3
D)
2 and 3
6.
Switched reluctance motor means
A)
Salient pole synchronous motor without
excitation winding
B)
A stepper motor with salient poles
C)
Synchronous motors with salient poles on stator
and rotor
D)
A stepper motor with
closed loop control and with rotor position sensor
7.
A DC series motor is accidentally connected to a
single phase AC supply. The torque produced will be
A)
Of zero average value
B)
Oscillating
C)
Steady and unidirectional
D)
Pulsating and
unidirectional
8.
The synchronous impedance method of finding the
voltage regulation by a cylindrical rotor alternator is generally considered as
A)
A pessimistic method
because saturation is not considered
B)
An optimistic method because saturation is not
considered
C)
A fairly accurate method even if power factor is
not taken into account while determining synchronous impedance
D)
A fairly accurate method when power factor is
taken into account while determining synchronous impedance
9.
Generally the no-load losses of an electrical
machine is represented in its equivalent circuit by
A)
Parallel resistance with
a low value
B)
Series resistance with a low value
C)
Parallel resistance with a high value
D)
Series resistance with a high value
10.
The power factor of a synchronous motor
A)
Improves with increase
in excitation and may even become leading at high excitations
B)
Decreases with increase in excitation
C)
Is independent of its excitation
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