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Resonant inductive displacement sensor for active magnetic bearings

2019; Elsevier BV; Volume: 287; Linguagem: Inglês

10.1016/j.sna.2019.01.011

1873-3069

Angelo Bonfitto, Ran Gabai, Andrea Tonoli, Luis M. Castellanos Molina, Nicola Amati,

Electric Motor Design and Analysis

This paper presents a resonant inductive sensor for radial displacement in Active Magnetic Bearing (AMB) systems. The device consists of a wire coil wound around a tooth of a conventional eight-pole radial actuator of the bearing. The proposed device is different from standard inductive sensor schemes since the sensing coil is excited by the electromagnetic field generated by the actuation coil and not by an external oscillator. The electromagnetic flux linked by the sensing coil is a function of the distance between the sensor and the levitated object whose position has to be measured. The output measurement voltage is amplified by means of an electric resonator circuit obtained by installing a capacitor on the terminals of the sensing coil. A qualitative model is developed and compared to an experimental apparatus. This model captures well the sensing phenomenon and can be used for designing such a sensor. The proposed device demonstrates good properties of resolution and sensitivity with a small and low-cost layout. Additionally, such sensor allows obtaining an inherent sensor/actuator collocation along the longitudinal direction of rotors, which is an advantage in AMB systems for rotating machinery since it allows simplifying the layout and avoiding instability problems.