Practical sensorless control for inverter-fed BDCM compressors

Brushless DC motors (BDCMs) possess higher efficiencies than the conventional induction motors and BDCMs have therefore been used widely in inverter-fed compressors. Since the Hall position sensors cannot work well in the high-temperature environment of refrigerants, sensorless control schemes play an important role in the application of inverter-fed BDCM compressors. Sensorless control for actual BDCM compressor is proposed and implemented. First, the sensorless circuits used have been analysed in detail to find the design rules of the circuit parameters for various compressor motors. Then, the limitations of sensorless control are discussed to develop a practical speed controller for BDCM compressors. The developed starting strategy and sensorless algorithms are presented and digitally implemented. Finally, some experimental results are displayed to demonstrate the proposed sensorless speed control for BDCM compressors.