Combined Rotor Position Estimation and Temperature Monitoring in Sensorless Synchronous Motor Drives

A novel approach is described in this paper, combining sensorless rotor position estimation with temperature monitoring. In particular, the rotor position is estimated by suitably manipulating the voltages induced in the cabling of the thermistors tasked to monitor the stator temperature. Since no additional cables and wirings are required, the only difference compared to a standard machine design consists in a different shaping of the thermistor connections in order to turn them in a set of search coils. Moreover, some typical drawbacks of sensorless position estimation techniques based on the manipulation of fundamental components of stator voltages and currents, such as those related to inverter non-linearities, stator resistance voltage drops, magnetic saturation and cross-coupling can be mitigated. A position tracking technique for synchronous motor drives has been also developed taking advantage from obtained search coils, fully independent from motor parameters. Simulations and experimental tests confirm the effectiveness of the proposed approach for two different types of synchronous motors.