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A 25 kW, three-phase 400 V (line), 50 Hz induction motor with a 2.5:1 reducing 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 using a pulley of 0.5 m in diameter and a slip ratio of 4.5%. The motor has a full-load efficiency of 91% and a rated power factor of 0.8 lagging. The stator 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 the induction motor under the above conditions and ignoring the losses. (ii) (!!!) the number of pole-pairs this induction motor must have to achieve this rotational speed. the full-load and start-up currents (in amps).

A 25 kW, three-phase 400 V (line), 50 Hz induction motor with a 2.5:1 reducing 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 using a pulley of 0.5 m in diameter and a slip ratio of 4.5%. The motor has a full-load efficiency of 91% and a rated power factor of 0.8 lagging. The stator 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 the induction motor under the above conditions and ignoring the losses. (ii) (!!!) the number of pole-pairs this induction motor must have to achieve this rotational speed. the full-load and start-up currents (in amps).

Introductory Circuit Analysis (13th Edition)
Introductory Circuit Analysis (13th Edition)
13th Edition
ISBN:9780133923605
Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
Chapter1: Introduction
Section: Chapter Questions
Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...
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A 25 kW, three-phase 400 V (line), 50 Hz induction motor with a 2.5:1 reducing 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 using a pulley of 0.5 m in diameter and a slip ratio of 4.5%. The motor has a full-load efficiency of 91% and a rated power factor of 0.8 lagging. The stator 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 the induction motor under the above conditions and ignoring the losses. (ii) (!!!) the number of pole-pairs this induction motor must have to achieve this rotational speed. the full-load and start-up currents (in amps).
Transcribed Image Text:A 25 kW, three-phase 400 V (line), 50 Hz induction motor with a 2.5:1 reducing 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 using a pulley of 0.5 m in diameter and a slip ratio of 4.5%. The motor has a full-load efficiency of 91% and a rated power factor of 0.8 lagging. The stator 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 the induction motor under the above conditions and ignoring the losses. (ii) (!!!) the number of pole-pairs this induction motor must have to achieve this rotational speed. the full-load and start-up currents (in amps).
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