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8. Three-phase Induction Motors > 8.18 - Solved Numerical Problems

8.18 Solved Numerical Problems

Example 8.3 A 3 hp, three-phase, four-pole, 400 V, 50 Hz induction motor runs at 1440 rpm. What will be the frequency of the rotor-induced EMF?

Solution:

 

images

 

Rotor speed,   Nr = 1440 rpm

 

images

 

Stator supply frequency, f = 50 Hz

Rotor induced EMF frequency, fr = Sf

= 0.04 × 50

 

= 2 Hz

Example 8.4 The frequency of the rotor-induced EMF of 400 V, three-phase, 50 Hz, six-pole induction motor is 2 Hz. Calculate the speed of the motor.

Solution:

 

images

 

Rotor frequency,   fr = Sf

or,   2 = S × 50

or,   S = 0.04

Again,   images

Substituting values images

or,   Nr = 960 rpm

Example 8.5 A slip-ring-type three-phase induction motor rotates at a speed of 1440 rpm when a 400 V, 50 Hz is applied across the stator terminals. What will be the frequency of the rotor-induced EMF?


  

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