A 25 kW, three-phase 400 V (line), 50 Hz induction motor with a 2.5:1reducing gearbox is used to power an elevator in a high-rise building.The motor will have to pull a full load of 500 kg at a speed of 5 m/s usinga pulley of 0.5 m in diameter and a slip ratio of 4.5%. The motor has afull-load efficiency of 91% and a rated power factor of 0.8 lagging. Thestator series impedance is (0.08 + j0.90) Q and rotor series impedance(standstill impedance referred to stator) is (0.06 + j0.60) Q.Calculate:(i) the rotor rotational speed (in rpm) and torque (in N·m) of theinduction motor under the above conditions and ignoring thelosses.(ii)(!!!)the number of pole-pairs this induction motor must have toachieve this rotational speed.the full-load and start-up currents (in amps).

Given:Power (P) = 25 kW = 25,000WLine Voltage (V) = 400 VFrequency (f) = 50 HzLoad mass = 500…

Answered: A 25 kW, three-phase 400 V (line), 50…

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter32: Three-phase Motors

Section: Chapter Questions

Problem 6RQ: Name three factors that determine the torque produced by an induction motor.

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A freewheeling DC motor is driven with 1000 rpm and a nominal load torque of 80Nm. The field circuit resistance is 200 and the armature circuit resistance is 0.2 O. The field coils are fed with a zero degree transmission angle through a single-phase fully controlled converter connected to a single-phase 240V source. The armature circuit is fed from a single phase 400V source through another fully controlled converter. Magnetic saturation has been neglected, the motor constant is given as 0.8 V - s / A - rad. Assuming that there is no fluctuation in armature and field current, find the control angle of the converter feeding the armature at nominal load. If you want to leave the question blank, click again on the option you marked.
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