Advance Angle Calculation for Improvement of the Torque-to-Current Ratio of Brushless DC Motor Drives.

Abstract: This paper presents a method of calculating an advance angle in order to increase the torque-to-current ratio of a brushless DC (BLDC) motor. The BLDC motor is widely used in various industrial fields because of its high energy density and low maintenance. Because the BLDC motor drives with a square-wave current of electrical 120 degrees duration, the phase current must be commuted every 60 electrical degrees of rotation. Owing to the inductance levels of the motor winding process, the commutation induces a phase lag and deviations from the ideal square-wave current form. These non-ideal characteristics reduce the torque-to-current ratio. Advancing the commutation timing can improve the torque-to-current ratio. This paper analyzes the torque performances of the BLDC motor and proposes a method of calculating the advance angle in order to improve the torque-to-current ratio. The simulation results of a 20W, 20,000rpm BLDC motor verify the effectiveness of the proposed calculation method. [Copyright &y& Elsevier]