Effect of insulating liquid viscosity on output force of a high-power synchronous electrostatic motor

Abstract

The output force of high-power electrostatic motors is defined by an internal electric field, and a strong electric field can cause air discharge unless the motors are operated within a dielectric liquid. Previous studies evaluated how the viscosity of a dielectric liquid can impact the output performance of a motor. While the viscous drag resistance increases with viscosity, the degradation of the output force was found to be negligible. However, the reason for this behavior was not clarified in those studies. This work clarifies the reason for the output behavior through numerical simulations and experiments. In the simulation, motion trajectories and motor output were analyzed for different operation speeds in different liquid viscosities. The results revealed that the existence of peaks in the force characteristics of the motor is the key to understanding a motor’s unique behavior within a viscous liquid. In a viscous liquid, the trajectories change such that the peak force is generated to compensate for the drag resistance. The simulations also revealed that the behavior only appears in one of the two types tested in the simulation, which differ in the smoothness of their force characteristics. The simulation results were verified in experiments. The experimental results reconfirmed the results of previous studies, and verified the findings of the simulations of this work.