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Maximum speed of 2 pole induction motor cannot be
750 rpm
1000 rpm
1500 rpm
3000 rpm
3000 rpm
Given: Number of poles P = 2, Frequency f = 50 Hz (assumed standard Indian supply frequency)
Number of poles P = 2, Frequency f = 50 Hz (assumed standard Indian supply frequency)
NsтАЛ=P120├ЧfтАЛ
Identify Synchronous Speed Formula
The synchronous speed NsтАЛ of an induction motor depends on the supply frequency f and the number of poles P.
NsтАЛ=P120fтАЛ
Calculate Synchronous Speed
Substitute f=50 Hz and P=2 into the formula to find the maximum possible speed.
NsтАЛ=2120├Ч50тАЛ=3000┬аrpm
Analyze Motor Speed vs Synchronous Speed
An induction motor always runs at a speed N less than the synchronous speed NsтАЛ due to slip. Therefore, it can never achieve the synchronous speed.
N<NsтАЛ=3000┬аrpm
D is correct because the synchronous speed of a 2-pole, 50 Hz motor is 3000 rpm, and an induction motor cannot reach or exceed this speed while operating as a motor.
This concept is fundamental to understanding the slip-speed relationship in all AC machines; remember that s=NsтАЛNsтАЛтИТNтАЛ, where s must be positive for motor action.