What is skewing of an induction motor:
The rotor or stator slot of the induction motor skewed through some angle so that the bars lie under alternate harmonic poles of the same polarity or other words, bars must be skewed through two pitches.
Generally motor manufacture do not skew stator slot. here see the picture as shown below. Actual rotor slots are in red colored, the skewed rotor slots are in red colored. The yellow color has some angle which is called skewing rotor.
Let us consider n in a machine with p poles. The number of nth order harmonic poles is np
The angle between two adjacent hormanic poles = 360/np
For elimination of nth harmonic by skewing, angle of skew = 720/n * p deg angle
The electrical angle of skew is = 720/n (p/2)= 360/n degree electrical
= 2pi/n electrical radian.
Advantage of skewing of an induction motor:
- Eliminate any type of harmonic
- Noise reduction
- To produce uniform torque
- Reduce the magnetic pulling
- Better voltage form