Abstract: Different sensor outputs with different interlayer added between the sensor and rotor are theoretically analyzed in view of the performance of differential transformer displacement sensor and its application in active magnetic bearing (AMB) system. The sensors are statically and dynamically calibrated and applied to both two degrees of freedom and five degrees of freedom AMB systems for static and dynamic suspensions. The results show that the linearity of the sensor is ±1.38%, sensitivity is 20.18 mV/μm in the measuring range of –0.5～+0.5 mm, and the cut-off frequency reaches 800 Hz. The sensor performance is not affected by non-magnetic layers according to the theoretical analysis result, but the eddy current, magnetic flux leakage, etc. In actual applications have an impact on the static and dynamic properties of the sensor. The two-degree-of-freedom magnetic rotor can be statically levitated, the vibration magnitude of rotor in the radial direction without the interlayer is less than 5 μm, and the magnitude is 10 μm when a non magnetic-conducting thin wall is installed between the sensor and the rotor. The five-degree-of- freedom magnetic rotor can be stably suspended and rotated up to 30 kr/min, and the vibration magnitude of rotor two ends in the radial direction is 25 μm. When a non magnetic-conducting thin wall is installed, the magnitude does not change, but the wave shape is not as regular as the former one. The results provide a theoretical and experimental foundation for the design of the differential transformer displacement sensor and its application in AMB system.

Key words: Active magnetic bearing, Differential transformer, Displacement sensor, Thin wall