Real-time thermal management of permanent magnet synchronous motors by resistance estimation

Real-time thermal management of electrical machines relies on sufficiently accurate indicators of internal temperature. One indicator of temperature in a permanent-magnet synchronous motor is the stator winding resistance. This study applies two current injection techniques to a commercially produced permanent-magnet servomotor, which are applicable under load and cause minimal disturbance to the shaft torque. The current injection techniques applied here enable the temporary boosting of resistive voltage and consequent application to low-resistance, high-voltage machines. The effectiveness of the approach is demonstrated by tracking the change in winding temperature during a 2 h load cycle.