It is advisable to avoid line starting of induction motor and use starter because____________?
(A) it will run in reverse direction
(B) it will pick up very high speed and may go out of step
(C) motor takes five to seven times its full load current
(D) starting torque is very high
What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?
(A) The slip of the motor will be 5%
(B) The rotor will not run
(C) The rotor will run at very high speed
(D) The torque produced will be very large
The stating torque of the slip ring induction motor can be increased by adding__________?
(A) external inductance to the rotor
(B) external resistance to the rotor
(C) external capacitance to the rotor
(D) both resistance and inductance to rotor
A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on full load. The machine has 6 poles. The slip of the machine will be__________?
(A) 0.01
(B) 0.02
(C) 0.03
(D) 0.04
The power scale of circle diagram of an induction motor can be found from__________?
(A) stator resistance test
(B) no-load test only
(C) short-circuit test only
(D) noue of the above
A change of 4% of supply voltage to an induction motor will produce a change of approximately ________?
(A) 4% in the rotor torque
(B) 8% in the rotor torque
(C) 12% in the rotor torque
(D) 16% in the rotor torque
The shape of the torque/slip curve of induction motor is__________?
(A) parabola
(B) hyperbola
(C) rectangular parabola
(D) straigth line
The vafcie of transformation ratio of an induction motor can be found by__________?
(A) open-circuit test only
(B) short-circuit test only
(C) stator resistance test
(D) none of the above
In three-phase induction motors sometimes copper bars are placed deep in the rotor to___________?
(A) improve starting torque
(B) reduce copper losses
(C) improve efficiency
(D) improve power factor
Which is of the following data is required to draw the circle diagram for an induction motor ?
(A) Block rotor test only
(B) No load test only
(C) Block rotor test and no-load test
(D) Block rotor test, no-load test and stator resistance test