A method for supplying pilot voltages for sensorless control of IPMSMs in the low speed area is proposed. The rotor position is estimated by measuring the current differentials, while pilot voltages are supplied. However, audible noise is produced by the supply. In this paper, we describe how utilization of the symmetrical carrier PWM and current differential detection method enables us to propose a sensorless drive method that does not apply the pilot voltage intentional.
- Current differential