A question about the current control for BLDC (Trapezoidal motor)

Hi,

I want to realize the torque control of the BLDC (Brushless DC motor with trapezoidal bEMF) through Simulink. As for the ideal motor, the phase current is DC (see Figure 1, named phase current ideal) and the required current can be calcuted by using the equation I=T/K, where I is the current, T is the requried torque and K is the torque constant. However, because of the inductance in the circuit, the phase current cannot be ideally a straight line. The attached model is the simulink I built where the phase voltage is kept constant and we can see from Figure 2 (named phase current actual) that the actual phase current is like a ripple and is not a straight line, so that the required phase current cannot be obtained through the equation I=T/K.

I am wondering how to realize the torque control by controlling the current in BLDC motor. I appreciate it very much if you could help me out.

Best regards.

Answer 1

[Jonas]

I did not open your Simulink model, but if the current rises so slowly, I would think either the inductance of your motor is too high or the applied voltage too low.

[haonan He]

Thanks for your reply, Jonas. I am trying to figure out how to realize the torque control through the current control. I know that the current rise can be made more quickly by adjusting the inductance and the supply voltage, but in reality, the current cannot be a straight line, so I appreciate it very much if you could tell me how to control the current in this scenario.