The Design and Implementation of a Sensorless Delta-Connected Brushless Direct Current Motor Drive for Home Appliances

The sensorless motor drive of Brushless Direct Current (BLDC) motors with wye-connected windings, now becomes accepted in many practical applications because it can solve the drawbacks of Hall sensors based motor drive. One of the most popular sensorless control schemes is based on the phase Back Electromotive Force (BEMF) or terminal phase voltage from the floated phase. Sensorless commutation signals are obtained from the detection of zero crossing points of the phase BEMF. However, it is impossible to adopt this technique for the delta-connected BLDC motors. Therefore, a sensorless motor drive with sensorless circuit based on the line-to-line terminal voltages for a delta-connected BLDC motor is proposed in this paper. Moreover, a low-pass filter with variable cut-off frequencies was designed successfully with a simple algorithm in this paper. Furthermore, the performance of the proposed sensorless control scheme was also compared to that of the Hall based control. Finally, the experimental results demonstrated that the sensorless motor drive was successfully developed for the delta-connected BLDC motor. The feasibility of the complete system was also validated.