Brushless DC motor (BLDC for short) is a permanent magnet synchronous motor driven by direct current (DC), which accomplishes an electronically controlled commutation system (commutation is the process of generating rotational torque in a motor by changing the phase current) It is in due course) rather than a mechanical commutation system. Unlike conventional brushed DC motors, in which the brushes make mechanical contact with the commutator on the rotor, thus forming an electrical path between the DC power supply and the rotor armature winding, BLDC motors use a permanent magnet rotor and a stator with a rotor for electrical commutation, so that the stator produces a rotating magnetic field with a uniform change in direction before the motor can follow the field and rotate.

BLDC motors can be built using different physical configurations. Depending on the stator winding, these can be configured as single-phase, two-phase or three-phase motors. However, the most commonly used is the three-phase BLDC motor with a permanent magnet rotor.

The armature coil is electronically switched at the rotor position by a transistor or silicon controlled rectifier so that the armature magnetic field is spatially orthogonal to the rotor magnetic poles. The force acting on the rotor thus causes it to rotate. Hall sensors or rotary encoders are most often used to sense the position of the rotor, and the rotor position feedback from the sensor helps determine when to switch the armature current.

The drive method of brushless direct motors can be divided into square wave drive and positive metaphorical wave drive according to different categories

1. Square wave drive is the simplest drive method. It switches the electronics ON/OFF according to the rotation angle of the rotor, and then changes the current direction of the stator coil, thus rotating the rotor. The rotor rotates once and the current direction is switched 6 times.

This method is the same as the drive principle of a brushed DC motor. The motor driver uses an inverter circuit to control the voltage via PWM. It is the most widely used drive method for sensorless motors.

The sine wave drive rotates the rotor by continuously changing the voltage of the stator coil in a sinusoidal manner according to the rotation angle of the rotor. The three phases of the motor are "delayed" for a specific period of time, depending on the frequency.

It is more efficient, generates less vibration and is less noisy than a square wave drive. The controller needs to monitor the rotor position. Typically, three Hall sensors are used to detect the position every 60 degrees, detecting the rotor position in real time and outputting a sine wave voltage that matches the rotor position. An inverter circuit is used to drive the motor, and the voltage is continuously varied by PWM control.