Electrical Machines Objective Questions
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Torque developed in the rotor is
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A 3phase, 50Hz, 4 pole induction motor is running at 1440 rpm and rotor input power is 2KW. Find the rotor output power?
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A smaller air gap in a induction motor helps to
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When slip is greater than 1, then the motor is in which of the following region?
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If we increase the rotor reactance value, the maximum torque will
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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?
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A 3phase, 50 Hz, 4 pole induction motor is running at 1440 rpm and rotor input power is 2KW. Find the rotor copper loss?
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Which one of the following statement is correct ? In an induction motor if the air gap is increased then
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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?
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The advantage of the double squirrel cage induction motor over single cage rotor is that its
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The rotor power output of 3phase induction motor is 15 KW. The rotor copper losses at a slip of 4% will be
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A 4 pole 50 Hz 1phase induction motor is running at 1470 rpm. Find the forward and backward slips?
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The supply voltage to an induction motor is reduced by 10%. By what percentage, approximately, will the maximum torque decrease?
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Which of the following is the best way of starting for slip ring induction motor?
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In an induction motor, air gap power is 10 Kw and mechanically developed power is 8 Kw. What are the rotor ohmic losses?
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Which of the following statements is/are correct?
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No load test on induction motor is conducted to find which of the following losses?
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A 3phase, 50 Hz, 4 pole induction motor is running at 1440 rpm. Find the rotor efficiency?
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Which of the following are the starting methods for squirrel cage induction motor?
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Blocked rotor test is used to find which of the following losses ?
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A 440 V, 3phase, 10 pole and 50 HZ synchronous motor delivering a torque of 50 Nm, delivers a power of
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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})?
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The crawling in the induction motor is caused by
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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
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In induction generator the slip is always
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In an induction motor, what is the ratio of rotor input to rotor copper loss?
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From no load to full load the slip will
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The speed of stator rotating magnetic field with respect to rotor rotating magnetic field?
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When applied rated voltage per phase is reduce to one half, the starting torque of three phase squirrel cage induction motor becomes
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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
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