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The frequency (fr) of the rotor current in an induction motor is given by the expression (s = slip, f = supply frequency)

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The frequency (fr) of the rotor current in an induction motor is given by the expression fr = (s. f ) (s = slip, f = supply frequency)

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asked May 17, 2018 in Induction Machine by Shimroz123
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A 6-pole, 50Hz, 3-φ induction motor is running at 950 r.p.m. and has Cu loss of 5kW. The rotor input is (a) 10 kW (b) 95 kW (c) 100 kW (d) 9.5 kW 

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The effect of increasing the length of air gap in an induction motor is to increase the (a) power factor (b) speed (c) magnetising current (d) air gap flux  

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At low values of slip, the torque of an induction motor is   (a) directly proportional to the square of the slip. (b) inversely proportional to the square of the slip. (c) directly proportional to the slip. (d) inversely proportional to the slip. 

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
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Slip test is performed to determine :  (A) Slip in an induction motor  (B) Xd and Xq in a salient pole alternator  (C) Synchronous impedance in an alternator  (D) Positive and negative sequence impedances of an alternator

asked Apr 29, 2018 in Electrical Machine by Shimroz123
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The torque developed by any 3-phase induction motor at 0.8 p.u. slip is (A) Full-load torque (B) unstable torque (C) starting torque (D) break down

asked Apr 28, 2018 in Electrical Machine by Shimroz123
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asked Apr 14, 2018 in Electrical Engineering by Shimroz123
2 answers 14 views

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asked May 14, 2018 in Induction Machine by Shimroz123
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asked Apr 5, 2018 in Electrical Engineering by Shimroz123
1 answer 15 views

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asked May 17, 2018 in Induction Machine by Shimroz123
1 answer 32 views

A 3-phase, 4-pole, 50Hz induction motor runs at a speed of 1440 rpm. The rotating field produced by the rotor rotates at a speed of ________ rpm with respect to stator field. (A) 1500 (B) 0 (C) 1440 (D) 60

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1 answer 14 views

Whether a given point in the S-plane lies on the Root Locus of a system can be determined by (A) Magnitude criterion (B) Angle Criterion (C) Both Magnitude and Angle Criteria (D) Break-in and Break-away Criteria

asked Apr 25, 2018 in Control System by Shimroz123
1 answer 15 views

A three-phase cage induction motor is started by direct-on-line (DOL) switching at the rated voltage. If the starting current drawn is 6 times the full load current, and the full load slip is 4%, then ratio of the starting developed torque to the full load torque is approximately equal to (A) 0.24 (B) 1.44 (C) 2.40 (D) 6.00

asked May 17, 2018 in Induction Machine by Shimroz123
1 answer 17 views

A 3-phase induction motor is driving a constant torque load at rated voltage and frequency. If both voltage and frequency are halved, following statements relate to the new condition if stator resistance, leakage reactance and core loss are ignored  1. The difference between synchronous speed and actual speed remains same 2. The airgap flux remains same 3. The ... . slip remains same Among the above, current statements are  (A) All (B) 1, 2 and 3 (C) 2, 3 and 4 (D) 1 and 4

asked May 18, 2018 in Induction Machine by Shimroz123
1 answer 38 views

The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

asked May 1, 2018 in Electrical Machine by Shimroz123
1 answer 29 views

An 8-pole, 50Hz, three-phase induction motor is running at 705rpm and has a rotor copper loss of 5kW. Its rotor input is (A) 5.06 kW (B) 0.3 kW (C) 100 kW (D) 83.33 kW

asked Apr 28, 2018 in Electrical Machine by Shimroz123
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Deep bar rotor construction is used in three phase induction motors to mainly: (1) Control speed (2) Control power factor (3) Increase starting torque (4) None of these

asked May 22, 2018 in Induction Machine by Shimroz123
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In the Squirrel cage induction motors, the rotor slots are usually a slight skew to reduce (A) Windage losses (B) Eddy currents (C) Accumulation of dirt and dust (D) Magnetic hum

asked May 12, 2018 in Induction Machine by Shimroz123
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For the circuit shown in figure, the Boolean expression for the output y in terms of inputs P, Q, R and S is

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