MCQs on Electrical Machines

Page 99 of 114. Go to page
01․ Stable operation of an induction motor
between zero slip and unity slip.
between 0.5 slip and 0.95 slip.
between zero slip and slip corresponding to maximum torque.
between slip corresponding to maximum torque and unity slip.

Under construction.
02․ In a 3 - Φ induction motor, the maximum torque is
varies as rotor resistance.
varies as the square of rotor resistance.
varies inversely as rotor resistance.
independent rotor resistance.

Under construction.
03․ A 3 - Φ induction motor usually operates on
unity power factor.
0.8 leading power factor.
0.8 lagging power factor.
0.6 lagging power factor.

Under construction.
04․ A three phase induction motor takes A amperes on full load at a power factor cosφ. The component responsible for producing magnetism is
Asinφ.
Atanφ.
Acosφ.
A / cosφ

Under construction.
05․ A 3 - Φ induction motor connected to 2 - Φ supply
will run at lower rpm.
will run at higher rpm.
may burn.
may run with fluctuation in speed and torque.

Under construction.
06․ A 3 - Φ induction motor while running on 25 % of rated load, has one of its fuses removed. The line current
will not change.
in two phase will reduce to zero.
in two phases will increase to compensate for the dead phase.
none of the above.

Under construction.
07․ In an induction motor 5 % change in supply voltage, will cause rotor torque variation of
2.5 %.
5 %.
10 %.
50 %.

Under construction.
08․ If single phase occurs in delta connected 3 - Φ induction motor
there will be no electric current in one phase.
there will be no electric current in two phase.
one phase is highly overloaded and others are slightly overloaded.
two phases are highly overloaded and no electric current in 3rd
Under construction.
09․ When a three phase induction motor is loaded
induced emf in the rotor as well as frequency increases.
induced emf in the rotor as well as frequency falls.
induced emf on the rotor decreases and its frequency increases.
indeced emf in the rotor increases and its frequency falls.

Under construction.
10․ In a core type transformer
HV winding is placed nearer to the core limb.
LV winding is placed nearer to the core limb.
any of the LV or HV can be placed nearer to the core limb.
HV and LV windings are placed in different core limbs.

LV winding is wound on the limb first. Then HV winding is placed on it and there is an insulation between LV and HV winding. In thin manner less amount of insulation needed. Also insulation between the core and the inner winding is stressed to low voltage.
<<<979899100101>>>