A 3 phase 50 hz source feeds the stator of both a 3 phase slip ring induction motor having 8 poles and a synchronous motor having 2 poles.The no. Of synchronous motor pole required for obtaining a frequency of 150 hz from the rotor srim
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In case of IM the torque is
inversely proportional to √slip.
directly proportional to slip.
directly proportional to slip2.
inversely proportional to slip.
The torque developed in IM is nearly proportional to
1 / V.
V2.
V.
1 / V2.
In case of 3 - Φ IM, plugging means
pulling the motor directly on line without a rotor.
locking of rotor due to harmonics.
interchanging two supply phases for quick stopping.
starting the motor on load which is more than the rated load.
When R2 is rotor resistance, X2the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running condition will be
sR2 = X2.
R2 = s2X2.
R2 = s2X2.
R2 = sX2.
The rotor electromotive force of the IM is observed to make 100 complete alterations per minute, calculated slip
3.33 %.
3 %.
0 .001 %.
none of the above.
Nichrome is an alloy of
nickel, chromium and iron.
silver, copper and nickel.
aluminium, tin and copper.
chromium, manganese and copper.
In a star - delta starting of an IM
reduced voltage is applied to the stator.
applied voltage per stator phase is 57.7 % of a line voltage.
line voltage is 57.7 % of stator voltage.
resistance is inserted in the rotor.
A 3 - Φ induction motor can also be referred to as a
asynchronous motor.
transformer.
repulsion motor.
shunt motor.
Which of the following methods of speed control is not affected through stator side?
Change of rotor resistance.
Change of number of pole.
Change of supply voltage.
Change of supply frequency.
The wound rotor type IM is used for____________speed operation.
constant.
maximum.
minimum.
variable.
The rotor speed of an induction motor is given by
Ns = 120f / p × ( 1 - s ).
Nr = 120f / p × (1-s).
Ns = 120f /p × ( 1 - r).
none of the above.
Pole changing methods are suitable only for ___________ type induction motor.
wound.
cage.
linear.
none of these.
In a 3 - Φ IM in order to eliminate cogging the number of stator slots must be
unequal to number of rotor slots and skewed in shape.
equal to number of rotor slots.
an integral multiple of number of rotor slots.
either (B) or (C).
A slip ring Induction motor runs at 290 rpm at full load, when connected to 50 Hz supply. Determine the number of poles and slip.
p = 20, s = 3.33 %.
p = 40, s = 5.79 %.
p = 60, s = 0.96 %.
p = 50, s = 4.43 %.
_____________ types of induction motor are widely used.
Slip ring IM.
Squirrel cage IM.
Single phase IM.
Three phase IM.
The rotor of a three phase induction motor has an impedance of 0.4 + j4 ohm per phase at standstill the maximum torque occurs at a slip of _____________.
10 %.
15 %.
25 %.
50 %.
The speed of a 50 Hz three phase induction motor under full load condition is 725 rpm the number of poles of the motor are ______________.
2.
4.
6.
8.
What will be the maximum power factor of an induction motor for dispersion coefficient of 0.05?
0.05.
0.905.
1.1.
20.
Value of specific electric loading of Induction motor is in the range of
400 - 4000 ampere conductor / mt.
5000 - 45000 ampere conductor / mt.
30,000 - 1,00,000 ampere conductor / mt.
40 - 400 ampere conductor / mt.
Larger values of air flux density is taken while designing IM for
larger output.
larger bore diameter.
both.
none.
0102030405
0607080910
11
0607080910
11
In case of IM the torque is
inversely proportional to √slip.
directly proportional to slip.
directly proportional to slip2.
inversely proportional to slip.
The torque developed in IM is nearly proportional to
1 / V.
V2.
V.
1 / V2.
In case of 3 - Φ IM, plugging means
pulling the motor directly on line without a rotor.
locking of rotor due to harmonics.
interchanging two supply phases for quick stopping.
starting the motor on load which is more than the rated load.
When R2 is rotor resistance, X2the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running condition will be
sR2 = X2.
R2 = s2X2.
R2 = s2X2.
R2 = sX2.
The rotor electromotive force of the IM is observed to make 100 complete alterations per minute, calculated slip
3.33 %.
3 %.
0 .001 %.
none of the above.
Nichrome is an alloy of
nickel, chromium and iron.
silver, copper and nickel.
aluminium, tin and copper.
chromium, manganese and copper.
In a star - delta starting of an IM
reduced voltage is applied to the stator.
applied voltage per stator phase is 57.7 % of a line voltage.
line voltage is 57.7 % of stator voltage.
resistance is inserted in the rotor.
A 3 - Φ induction motor can also be referred to as a
asynchronous motor.
transformer.
repulsion motor.
shunt motor.
Which of the following methods of speed control is not affected through stator side?
Change of rotor resistance.
Change of number of pole.
Change of supply voltage.
Change of supply frequency.
The wound rotor type IM is used for____________speed operation.
constant.
maximum.
minimum.
variable.
The rotor speed of an induction motor is given by
Ns = 120f / p × ( 1 - s ).
Nr = 120f / p × (1-s).
Ns = 120f /p × ( 1 - r).
none of the above.
Pole changing methods are suitable only for ___________ type induction motor.
wound.
cage.
linear.
none of these.
In a 3 - Φ IM in order to eliminate cogging the number of stator slots must be
unequal to number of rotor slots and skewed in shape.
equal to number of rotor slots.
an integral multiple of number of rotor slots.
either (B) or (C).
A slip ring Induction motor runs at 290 rpm at full load, when connected to 50 Hz supply. Determine the number of poles and slip.
p = 20, s = 3.33 %.
p = 40, s = 5.79 %.
p = 60, s = 0.96 %.
p = 50, s = 4.43 %.
_____________ types of induction motor are widely used.
Slip ring IM.
Squirrel cage IM.
Single phase IM.
Three phase IM.
The rotor of a three phase induction motor has an impedance of 0.4 + j4 ohm per phase at standstill the maximum torque occurs at a slip of _____________.
10 %.
15 %.
25 %.
50 %.
The speed of a 50 Hz three phase induction motor under full load condition is 725 rpm the number of poles of the motor are ______________.
2.
4.
6.
8.
What will be the maximum power factor of an induction motor for dispersion coefficient of 0.05?
0.05.
0.905.
1.1.
20.
Value of specific electric loading of Induction motor is in the range of
400 - 4000 ampere conductor / mt.
5000 - 45000 ampere conductor / mt.
30,000 - 1,00,000 ampere conductor / mt.
40 - 400 ampere conductor / mt.
Larger values of air flux density is taken while designing IM for
larger output.
larger bore diameter.
both.
none.
0102030405
0607080910
11
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