Abstract: The critical speed of the rotating system of the drum washing machine under different working conditions is studied, and a specific type of drum washing machine is taken as an example. The rotating system model of the drum washing machine are built by using super element technology. The complex characteristics value of the rotating system considering the gyroscopic effect are solved by the modal method, and the Campbell diagrams of no-load, eccentric and various load conditions are obtained. The results show that the gyro effect reduces the first critical speed of the rotating system under different working conditions and increases the double critical speed. The critical speed of the rotating system under three different conditions is compared. The minimum critical speed of the rotating system is 1494 r/min under loaded conditions, so the dewatering speed of the rotating system is designed between 0.5 and 0.8 times the minimum critical speed, which is 747 r/min and 1195 r/min. The conclusions provide reference and guidance for the safety design of the rotating system of the drum washing machine.

Key words: Critical speed, Drum washing machine, Super element, Gyroscopic effect, Campbell diagrams