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Induction Motor 2

This document contains four problems related to calculating values for induction motors operating at different loads and voltages based on given motor specifications and operating parameters: 1. It asks to calculate the rotor current, power input, copper loss, power developed, and torque for a 4-pole, 2 HP, 220 V, 60 Hz, 3-phase induction motor operating at 2.5% slip. 2. It asks to calculate the starting torque and current for a 4-pole, 20 HP, 220 V, 3-phase induction motor if the voltage applied is reduced to 130 V. 3. It asks to calculate the efficiency of a 400 V, 60 Hz, 6-pole, wye-connected, 3

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528 views2 pages

Induction Motor 2

This document contains four problems related to calculating values for induction motors operating at different loads and voltages based on given motor specifications and operating parameters: 1. It asks to calculate the rotor current, power input, copper loss, power developed, and torque for a 4-pole, 2 HP, 220 V, 60 Hz, 3-phase induction motor operating at 2.5% slip. 2. It asks to calculate the starting torque and current for a 4-pole, 20 HP, 220 V, 3-phase induction motor if the voltage applied is reduced to 130 V. 3. It asks to calculate the efficiency of a 400 V, 60 Hz, 6-pole, wye-connected, 3

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Perfectly Amazing Vdeos
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© © All Rights Reserved
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Problems

1. A four pole, 2 HP, 220 V, 60 Hz, 3-phase induction motor has a delta connected stator and a wye-connected rotor. The
ratio is 4:1. At full-load, the slip is 2.5%. If the rotor resistance per phase and the blocked-rotor reactance per phase are
0.3 ohm and 1 ohm respectively, calculate;

a. the rotor current per phase

b. the rotor power input at full-load

c. the rotor copper loss at full load

d. the rotor power developed at full load

e. the rotor torque developed

2. A four pole, 20 hp, 220 V, 3-phase induction motor has a starting torque of 350 lb-ft and an instantaneous starting line
current of 750 A when started at rated voltage. If a reduced voltage of 130 V is applied to its terminals, calculate;

a. the starting torque

b. the starting current

3. A 400 V, 60 Hz, 6-poles wye-connected, 3-phase induction motor draws 75 kW with a line current of 100 A. The core
loss is 2 kW; Friction and windage loss is 1.2 kW. The stator’s resistance between two terminals is 0.35 ohms. What is
the efficiency if the motor runs at a slip of 2.5%?

4. A 10 hp, 60 Hz, 4-pole, wye-connected, 3-phase induction motor at normal operation draws power from the 220 V
source of 7.5 kW at 22 A, when the slip is 2.5%. At no load-test, the power drawn is 600 W and the line current is 7 A.
When the blocked-rotor test was performed the power and the current drawn were 550 W and 15 A respectively.
Calculate the efficiency and the torque in lb-ft at the normal operation.

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