Cogging torque and acoustic noise reduction in permanent magnet motors by teeth pairing

This paper investigates reduction of cogging torque and acoustic noise in permanent magnet motors with larger stator slot opening. Using an energy method with Fourier series expansion, cogging torque is analytically determined with airgap MMF function and airgap permeance function. It shows that there exist several tooth widths which minimize the cogging torque. It also proposes a teeth pairing with two different types of tooth width which can effectively reduce the cogging torque and thus the acoustic noise. Experimental results show that the proposed teeth pairing reduces the cogging torque by 85% and the acoustic noise by 3.1 dB.