Field expansion of low speed in sensorless 120-degree conduction drives of Brushless DC Motor

In certain motor applications, a sensor cannot be used because of restrictions of temperature environment or size. One example is a hand piece used in dentistries. It is required that this should be performed correctly at a low speed. Therefore, control expansion of the low speed field by the BLDCM sensorless drive is required. In this paper, the sensorless drive using a load angle performs control expansion of the low speed field of BLDCM. In conclusion, it was determined that drive was possible without step out also in a low speed field.