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.