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The general brushless DC motor control drives are always equipped with Hall sensor or encoder to provide rotor position feedback. Using those rotor position feedback signals can provide the next driving vector. Based on digital signal controller (DSC), the paper uses pulse width modulation (PWM) three-phase inverter to drive the motor which is equipped with Hall sensor. Therefore, six-step square wave vector control is applied to reach position control. However this control method can only produce smaller torque with power angle of 60degree. This study presents an angle offset method to obtain maximum torque with power angle of 90 degree. Finally some experiment results are proposed to verify that the motor is driven with maximum torque.

This experiment designed and fabricated the controller of a brushless DC motor which equips with Hall sensors. The motor driver was fabricated with Microchip dsPIC30F4011 chip which read feedback signals from the Hall sensors. The chip connected to the three-phase six-arm switching inverter circuit then connected to the motor. In such a way the user can drive the motor by position control using the method of six-step square wave vector control. But this conventional control method can just reach a torque of 60 degree power angle. In this study the vector synthesis method was employed to produce a maximum torque of 90 degree power angle. This method can decrease the kinetic energy loss of torque. From the experimental results, it is found that with 90 degree power angle the motor power consumption decreased, torque enhanced and rotation speed increased when compared with 60 degree power angle.