Design of Dual Skewed Rotor in Cage Induction Motor for Reducing Synchronous Parasitic Torque

Abstract

Dual skewed rotor is an improved skewed rotor pattern in suppressing the slot harmonics. However, in order to lessen synchronous parasitic torque, the relevant structural parameters should be modified for different slot combinations. According to the unified expressions of magnetic flux densities, the general harmonic torque could be calculated with the virtual displacement method. Then, the synchronous torque ratio is proposed to reflect the effect of synchronous parasitic torque on the starting torque. Under the premise of the assumed parameter range, the rotor type and minimized skewed angle are determined for three kinds of slot combinations. The normal skewed rotor could be seen as a special topology of dual skewed rotor. Finally, the validity of designing process is verified by the comparison of simulation study and experimental results.

Back EMF Waveform Comparison and Analysis of Two Kinds of Electrical Machines

“…However, compared with the straight slot of the rotor, the skewed slot of the rotor can improve the sinusoidal degree of back EMF waveforms. The detailed theoretical research of skewed-slot-type rotor can be seen in References [22][23][24]. In this section, the discrepancy between the straight-slot-type rotor and skewedslot-type rotor is discussed through simulation and harmonics analysis.…”

“…For the straight-slot-type rotor of the FSPM machine and VFMPM machine, if we divide the mechanical rotating degree  into N equal parts, and simultaneously calculate the straight-slot-type back EMF waveform with different mechanical rotating The detailed theoretical research of skewed-slot-type rotor can be seen in References [22][23][24]. In this section, the discrepancy between the straight-slot-type rotor and skewed-slot-type rotor is discussed through simulation and harmonics analysis.…”