Abstract: With the popularization of dryer products in daily life, the problem of ripping sound of dryer becomes more and more prominent. By analyzing the causes of rippling sound for the dryers and its induction motor. On the basis of mechanism research, according to the beat characteristics of the motor, the excitation source causing the beat vibration is analyzed. It is theoretically concluded that the interaction between the electromagnetic excitation generated by the fundamental magnetic field and the mechanical excitation force caused by the misalignment of the rotor is the main cause of the beat vibration. By interchanging rotor experiment and testing the rotor runout, the theoretical analysis is verified, and it is proposed that the rotor bending deformation will lead to beat vibration, which provides theoretical guidance for eliminating the rippling sound of induction motor.

Key words: Induction motor, Rippling sound, Beat, Bending rotor