Analysis to the dither in torsion coupling of low speed rotor

In order to explain the causation of dither present in the low speed rotor with solid lubrication, the relationship between rotor and bearing with the disturbance of torsion coupling is established, then the phenominon of unstability can be explained by slight oscillation. First, based on the moment balance function, the tortion balance equation is established with among motor,rotor and bearing. Then one order mode of the rotor is driven by different frequencies PWM pulses, the response of the speed approved that the resonance frequency can’t be neglectable. Finally, the race coupling frequency with different speed and granulation which provided an area of optimum choice for the PWM pulse. The flexible characteristic and the granulation of the race is the direct reason which induce the imbalance,According to the inducement of torsion coupling, while the PWM pulse provide power for the coupling, all that result with low speed dither.