Brushless DC Motor Selection Guide

Brushless DC (BLDC) motor uses semiconductor switching devices to realize electronic commutation, namely replacing traditional contact commutator and brush with electronic switching devices. It has the advantages of high reliability, no commutation spark and low mechanical noise, and is widely used in electronic instruments and automated office equipment.
Next ATO will introduce how to select a high power and high torque BLDC motor.

Torque, Speed Selection
On occasions of adjustable power supply voltage, the BLDC motor specifications whose torque and speed are close to the corresponding rated value of the product can be selected according to the actual needs, and then getting the required speed by changing the voltage. On occasions of constant power supply voltage, if there is no suitable BLDC motor for selection, the appropriate specifications can be selected according to the torque, and the voltage and speed of the product can be adjusted appropriately.

Power Selection
Maximum output power of the motor is limited. If the selected power is too small, the brushless DC motor will be overloaded when load exceeds its rated output power, and there will be motor heating, vibration, speed drop, abnormal sound and other phenomena. When the brushless DC motor is seriously overloaded, the motor will be burned down. But if the selected power is too large, it will cause economic waste. Therefore, it's very important to choose a reasonable power for motor.

Voltage Selection
Voltage is supplied by an electronic switching circuit controlled by the output of a position sensor. A right voltage should be firstly selected when choosing a brushless DC motor product, and the rated voltage should be according to customer's needs, then the driver voltage parameters should be selected correspondingly. Notice that the voltage used should not exceed the range specified by the driver in free-load and full-load.

Current Selection
When choosing the peak current of the controller, if the rated input current of motor is known to be Ir(A), then the peak current Ip(A)=2*Ir, otherwise, there is no engineering allowance for the output current during the operation of the controller. If the rated output power (or maximum output power) Pr(W) and driving voltage of the BLDC motor are known, then the peak current Ip(A)≧ 4*Pr/Vr.

Resistance Selection
Another key point is the insulation requirements of power. In order to ensure the normal operation of the controller, the insulation resistance between the Hall wire ground wire and the motor winding wire, the Hall ground wire winding wire and the housing of the motor shall be greater than 100 megaohms 500VDC, so as to withstand 600VAC/50Hz/1mA/1 second voltage withstand no breakdown.