How to Select a Right BLDC Motor Controller?

Motor controller is an integrated circuit which controls the motor to work by the set direction, speed, angle and response time through active operation. In electric vehicles, the functions of motor controller are to convert the electric energy stored by power battery into the electric energy needed to drive the motor according to the instructions of gear, throttle and brake, so as to control the starting operation, forward and backward speed and climbing force of electric vehicles, or to help brake the electric vehicles and store partial braking energy in power batteries. It's one of key parts of the electric vehicles.

1. Choose the controller that matches the type of motor. For example, DC brush, DC brushless, square wave or sinusoidal wave, Hall sensor or Hall sensorless.

2. Before selecting a controller, observe first if the motor power marked is the rated power or maximum power. If it's the rated power, the matched motor controllers can be selected according to 2-3 times rated power. For example, if the rated power marked on the motor is 650W and the voltage is 48V, then a motor controller with a rated voltage of 48V and the maximum output power of 1.3KW~2KW shall be chosen. If the maximum power is marked, a motor that has a smaller power can be selected.

3. Match motor parameters. Taking the high torque brushless DC motor as an example, it doesn't need to match special parameters for square wave controller no matter it has Hall or no Hall. If the hall sinusoidal controller has speed output, the motor pole pairs, speed and other parameters shall be matched. When matching a Hall-free sinusoidal wave, parameters of phase inductance, phase resistance, pole logarithm and maximum speed of motor shall be known.

What are the influences if the BLDC motor controller power is too small or too large?

If the BLDC motor controller power is too small. For example, maximum output power of 60V motor is 2.3KW, however, the 60V controller only select a maximum power of 800W. For example, the maximum average current of a 60V 800W controller is 13.3A, it's set on software that the the phase current protection value of motor blocking is 3 times of the average current, namely the phase current protection value shall be 40A. The maximum average current of a 60V 2.3KW motor is 33.3, assuming that the phase current protection value of matched motor controller is also set as three times of the average current, namely 100A. If a 800W BLDC motor controller is matched with a 2.3KW motor, the controller is equivalent to a small horse-drawn cart, and the controller will burn the power tube due to the power tube and heat dissipation problems. If the controller software does not have phase current limiting protection, the damage rate of the controller will be higher.

Finally, if the BLDC motor controller selects a larger power, the motor's output phase current will be greater than its maximum bearing capacity when it works under heavy load. The brushless DC motor would not be damaged in short-term light load, but if it works at heavy load for a long time, the motor would heat seriously, thus damaging the Hall sensor inside the motor and even burning the motor's stator winding.