New initial position detection technique for three-phase brushless DC motor without position and current sensors

This paper presents a new detection technique of initial position for a three-phase brushless DC motor which does not require any current and position sensors, and thereby significantly reduces the cost. The fundamental principle of the technique is to determine the initial position of the permanent magnet by the time periods of discharge of stator windings, which are excited before discharge. As compared to previous approaches, the presented technique does not cause any rotation during detection, and it is therefore very promising for particular kinds of applications, which do not allow the motor to rotate potentially in the wrong direction during initial position detection, e.g., electrical vehicles. As compared to earlier techniques, the presented technique dramatically simplifies the detection procedures and cost. Experimental results derived from a field-programmable gate-array-based control system are presented to demonstrate the feasibility of the presented technique.