b) A 20kW, 4-pole induction motor is designed to operate from a 440V, 50Hz, three-phase supply, and when operating at full power on this supply it runs at 1470RPM. The motor efficiency is 90% under both conditions. (i) What supply frequency will be needed to make this motor run at 1270RPM while delivering a shaft power of 12.5kW? (ii) If the motor were supplied from a sinusoidal variable frequency source, what voltage and current will need to be supplied to it when running at 1365 RPM at 12.5kW if the power factor of the motor is 0.85?

b) A 20kW, 4-pole induction motor is designed to operate from a 440V, 50Hz, three-phase supply, and when operating at full power on this supply it runs at 1470RPM. The motor efficiency is 90% under both conditions. (i) What supply frequency will be needed to make this motor run at 1270RPM while delivering a shaft power of 12.5kW? (ii) If the motor were supplied from a sinusoidal variable frequency source, what voltage and current will need to be supplied to it when running at 1365 RPM at 12.5kW if the power factor of the motor is 0.85?

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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b) A 20kW, 4-pole induction motor is designed to operate from a 440V, 50Hz, three-phase supply, and when operating at full power on this supply it runs at 1470rpm. The motor efficiency is 90% under both conditions. What supply frequency will be needed to make this motor run at 1270rpm while delivering a shaft power of 12.5kW?
A 110 V, 60 Hz, 6 – pole single phase induction motor 1/3 hp has the following equivalent circuit impedances: RI = 1.52 ohm, R2 = 3.13 ohm and x1 =2.10 ohm, x2 =1.56 ohm. Xm=58.2 ohm, The Friction, windage and stry losses =16W, the core loss = 35 W, For a slip of 0.05, calculation (a) input current, (b) power factor, (c) developed power, (d) output power, (e) speed (f) in put power (g) air gab power (h) T ind (i) T load 6) efficiency.
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7- A 6-pole, 50-Hz, 3-0 induction motor is running at 950 rpm and has rotor Cu loss of 6 kW. Its rotor input is......kW (a) 120 (b) 60 (c) 6.3 (d) 66 8- The number of slip rings on a squirrel cage induction motor is usually (a)Two (b) Three (c) Four (d) None
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