Determination of torque–speed–current characteristics of a brushless DC motor by utilizing back-EMF of non-energized phase

Abstract This paper presents a method to determine the torque constant and the torque–speed–current characteristics of a brushless DC (BLDC) motor by utilizing back-EMF variation of nonenergized phase. It also develops a BLDC motor controller with a digital signal processor (DSP) to monitor its current, voltage and speed in real time. Torque–speed–current characteristics of a BLDC motor are determined by using the proposed method and the developed controller. They are compared with the torque–speed–current characteristics measured by dynamometer experimentally. This research shows that the proposed method is an effective method to determine the torque constant and the torque–speed–current characteristics of the BLDC motor without using dynamometer.