Related Questions

While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by
A induction motor torque in field winding
B induction motor torque in damper winding
C eddy current and hysteresis torque in pole faces
D reHetance motor torque due to saliency of the rotor
E all of the above methods
For starting a D.C. motor a starter is required because
A It limits the speed of the motor
B It limits the starting current to a safe value
C It starts the motor
D None of the above
In a star-delta starter of an induction motor
A Resistance is inserted in the stator
B Reduced voltage is applied to the stator
C Resistance is inserted in the rotor
D Applied voltage per stator phase is 57.7% of the line voltage
A wound rotor induction motor is preferred, as compared to squirrel cage induction motor, when major consideration is
A Slop speed operation
B High starting torque
C Low windage losses
D All of the above
While starting a synchronous motor by induction motor action, field winding is usually
A connected to D.C. supply
B short-circuited by low resistance
C kept open-circuited
D none of the above
A direct on line starter is used: for starting motors
A Up to 5 H.P.
B Up to 10 H.P.
C Up to 15 H.P.
D Up to 20 H.P.
A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because
A synchronous motor has no slip
B stator supply is not required to produce magnetic field
C mechanical load on the rotor remains constant
D synchronous motor has large airgap
The power factor of a synchronous motor is better than that of induction motor because
A stator supply is relieved of responsibility of producing magnetic field
B mechanical load on the motor can be adjusted
C synchronous motor runs at synchronous speed
D synchronous motor has large air gap
In a pre-stressed member it is advisable to use
A Low strength concrete only
B High strength concrete only
C Low strength concrete but high tensile steel
D High strength concrete and high tensile steel
The starting torque of a three phase induction motor can be increased by
A Increasing slip
B Increasing current
C Both (A) and (B)
D None of the above

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