Noise and cogging torque reduction in brushless DC ceiling fan

This paper presents the improvements in the design of a three phase BLDC motor for noise reduction. The end application of BLDC motor is a ceiling fan. Acoustic noise spectrum of the motor is captured and analyzed. It is shown that, the cogging torque is the dominant cause of the acoustic noise. Two cogging torque reduction techniques namely - stator tooth pole shaping and magnet skew by single step, are analyzed and implemented for noise reduction. A prototype of the designed motor is fabricated to validate the analysis. Noise spectrum of the motor is measured to confirm the reduction in noise level. Final results show that the noise reduces by 7.1 dB.