A Novel Inductive Sensor Input Circuit with Improved Tolerance to Non-Concentricity with Touch-Down Bearings

When using inductive sensors, non-concentricity between the sensor and touch-down bearing stators of an active magnetic bearing (AMB) system can result in the sensor signal being “offset” within the touch-down bearing clearance. The resulting signal will have a larger amplitude at the extremes of motion compared to a well-centered system. A novel signal conditioning circuit is presented which allows the signal to be “re-centered” prior to demodulation. The impact of this circuit on required machining tolerances and sensor noise levels is discussed. We also present an implementation that is well-suited to automated and remote commissioning and the techniques used to set up the sensor sub-system during such a commissioning.