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.
The main purpose of skewing is to reduce the magnetic logging between the starter and the rotor.
Generally, motor manufacture does not skew the 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 harmonic 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.
Some times, the rotor will be skewed in V shape. It is called “V” view skewing. v skewing rotor is mainly used in the car motors to eliminate the vibration.
The noise reduction of v skewing is better than the above linear skewing rotor. But costwise the linear skewing is cheaper.
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