Analysis and Experiment of Self-Differential Eddy-Current Sensor for High-Speed Magnetic Suspension Electric Machine

An electric machine supported by an active magnetic bearing (AMB) can realize ultrahigh speed and high power density, and it is developing toward the trends of higher rotation speed and higher power density. The displacement sensor used for an AMB is one of the most important components in a magnetic suspension electric machine, so improving the dynamic response and the resolution of the displacement sensor become a critical technology. In this paper, a novel self-differential eddy-current displacement sensor (ECDS) based on the Hartley principle for a high-speed magnetic suspension electric machine is proposed and verified. First, the integral structure of the ECDS probe and the novel design scheme are presented. Second, the phase advance network method is described in detail to improve the dynamic characteristic of the sensor. Third, the detailed suppression procedure of the sensor-to-sensor crosstalk noise is given to improve the sensor's resolution. Finally, a series of experiments is carried out on two typical prototypes of a high-speed magnetic suspension electric machine. The experimental results indicate that the proposed ECDS with high dynamic response and resolution is valid in the application of the high-speed magnetic suspension rotating machinery in industrial applications.