Electrical Machines Objective Questions
0%
Blocked rotor test is used to find which of the following losses ?
Correct!
Wrong!

In an induction motor, air gap power is 10 Kw and mechanically developed power is 8 Kw. What are the rotor ohmic losses?
Correct!
Wrong!

An induction motor is started using auto transformer and it has a full load slip(S_{f}) of 0.02. Its starting current(Ist) is 3 times its full load current(If). What is the ratio of starting torque(T_{st}) to full load torque(T_{f})?
Correct!
Wrong!

The crawling in the induction motor is caused by
Correct!
Wrong!

A starting torque of 40 Nm is developed in an induction motor by an auto transformer starter with a tapping of 30%. If the tapping of auto transformer is 60%, then what is the starting torque?
Correct!
Wrong!

Which of the following is the best way of starting for slip ring induction motor?
Correct!
Wrong!

A 440 V, 3phase, 10 pole and 50 HZ synchronous motor delivering a torque of 50 Nm, delivers a power of
Correct!
Wrong!

An induction motor having 8 poles runs at 727.5 rpm. If the supply frequency is 50Hz, the emf in the rotor will have a frequency of
Correct!
Wrong!

Which of the following are the starting methods for squirrel cage induction motor?
Correct!
Wrong!

When applied rated voltage per phase is reduce to one half, the starting torque of three phase squirrel cage induction motor becomes
Correct!
Wrong!

A 4 pole 50 Hz 1phase induction motor is running at 1470 rpm. Find the forward and backward slips?
Correct!
Wrong!

In induction generator the slip is always
Correct!
Wrong!

The rotor power output of 3phase induction motor is 15 KW. The rotor copper losses at a slip of 4% will be
Correct!
Wrong!

A smaller air gap in a induction motor helps to
Correct!
Wrong!

No load test on induction motor is conducted to find which of the following losses?
Correct!
Wrong!

Which of the following statements is/are correct?
Correct!
Wrong!

If we increase the rotor reactance value, the maximum torque will
Correct!
Wrong!

A 3phase, 50 Hz, 4 pole induction motor is running at 1440 rpm and rotor input power is 2KW. Find the rotor copper loss?
Correct!
Wrong!

In an induction motor, what is the ratio of rotor input to rotor copper loss?
Correct!
Wrong!

Torque developed in the rotor is
Correct!
Wrong!

The supply voltage to an induction motor is reduced by 10%. By what percentage, approximately, will the maximum torque decrease?
Correct!
Wrong!

A 3phase, 50Hz, 4 pole induction motor is running at 1440 rpm and rotor input power is 2KW. Find the rotor output power?
Correct!
Wrong!

The advantage of the double squirrel cage induction motor over single cage rotor is that its
Correct!
Wrong!

A 3phase, 50 Hz, 4 pole induction motor is running at 1440 rpm. Find the rotor efficiency?
Correct!
Wrong!

From no load to full load the slip will
Correct!
Wrong!

An induction motor has a full load slip of 0.04. Its starting current is 5 times its full load current. what is the ratio of starting torque to the full load torque?
Correct!
Wrong!

Which one of the following statement is correct ? In an induction motor if the air gap is increased then
Correct!
Wrong!

An induction motor when started on no load does not accelerate up to full speed but runs at 1/7th of the rated speed. The motor is said to be
Correct!
Wrong!

When slip is greater than 1, then the motor is in which of the following region?
Correct!
Wrong!

The speed of stator rotating magnetic field with respect to rotor rotating magnetic field?
Correct!
Wrong!
