Abstract: Sommerfeld effect is a nonlinear jumping phenomenon caused by the failure of a non-ideal motor to provide enough power near the critical speed of the system to enable the system to pass through the resonance region smoothly. Sommerfeld effect and unbalanced response of an induction motor driven single disk rotor system with eccentric mass are studied. The dynamic model of induction motor is introduced into the rotor system, and the induction motor rotor dynamic model is established. It is found that Sommerfeld effect will occur in the induction motor-rotor system based on fully considering the interaction between induction motor and rotor system. The influences of the eccentric mass on Sommerfeld effect and unbalanced response are analyzed. The results show that when the mass ratio of eccentric mass to total rotor mass η is about less than 0.026, namely η<0.026, since the motor can provide enough power to ensure the rotor system smoothly pass the critical speed, Sommerfeld effect will not occur in the induction motor-rotor system. When 0.026 < η < 0.083, since the max electromagnetic torque provided by the motor is less than the output torque required for the rotor system to smoothly pass the critical speed, Sommerfeld effect will occur. When η>0.083, with the supply frequency increasing, the induction motor will not provide enough power to make the rotor system pass through the critical speed, and the rotor system's speed will always be lower than the critical speed. The research can provide reference for the power design and selection of rotor system.

Key words: rotor system, induction motor, Sommerfeld effect, nonlinear jump