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A 4 pole, 50 HzIM operates at 7% slip. The frequency of EMF induced in the rotor will be ________.
2.5 Hz
1.5 Hz
0.5 Hz
3.5 Hz
5 Hz
The frequency of the rotor EMF in an induction motor is directly proportional to the slip of the motor. It is calculated by multiplying the supply frequency by the slip.
IS 325:1996
The frequency of the rotor EMF in an induction motor is directly proportional to the slip of the motor. It is calculated by multiplying the supply frequency by the slip.
frтАЛ=s├Чf тАФ where frтАЛ is rotor frequency, s is slip, and f is supply frequency.
s=NsтАЛNsтАЛтИТNrтАЛтАЛ тАФ definition of slip in an induction motor.
As the rotor rotates at a speed NrтАЛ relative to the synchronous speed NsтАЛ of the rotating magnetic field, the relative speed is (NsтАЛтИТNrтАЛ). The rotor frequency frтАЛ is determined by the rate at which the magnetic flux cuts the rotor conductors, represented as frтАЛ=s├Чf.
At standstill (slip = 1), rotor frequency equals supply frequency.
At synchronous speed (slip = 0), rotor frequency is zero.
The 4-pole count is irrelevant for calculating frequency once the slip and supply frequency are known.
Simple linear relationship between slip and frequency
Independent of the number of poles
Rotor frequency decreases as speed increases
Cannot be measured directly without rotor sensors
Vector control in induction motor drives
Slip ring induction motor performance testing
Calculation: frтАЛ=0.07├Ч50=3.5┬аHz.
The provided option D (3.5 Hz) is the correct calculation. Options A, B, and C are mathematically incorrect for the given parameters.
D is correct тАФ The rotor frequency is calculated as 0.07├Ч50=3.5┬аHz.
Remember that the rotor frequency frтАЛ is also known as slip frequency; if you encounter a problem asking for slip speed in RPM, use NslipтАЛ=s├ЧNsтАЛ.
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