Efficiency Comparison of PWM-Controlled and PAM-Controlled Sensorless BLDCM Drives for Refrigerator Applications

For inverter-controlled brushless DC motor (BLDM) drives, the inverter can be controlled by either Pulse-Width Modulation techniques with constant DC-link voltage or Pulse-Amplitude Modulation (PAM). PAM modulates the inverter power devices using 120-degree modulation technique and controls the amplitude of DC-link voltage. The advantages and disadvantages of PWM and PAM are assessed using BLDCM drives which are applied to refrigerator. The results show that the PAM control provides higher efficiency as compared with PWM control. To our best knowledge, the reason for this remark is because that the modulation index or duty ratio can be maintained at higher level by varying the DC-link voltage. Because of this, THD and harmonics can be reduced as compared to PWM approach. Experimental results derived from a MCU-controller BLDM drives will be presented for comparison.