How does a BLDC (Brushless DC) motor rotate?

The rotation of a BLDC motor is achieved by electronically controlling the sequence of current in the stator windings, creating a rotating magnetic field that attracts the permanent magnet rotor to rotate continuously.

1. Structural Basics: The stator contains multiple sets of winding coils that generate a controllable magnetic field when energized. The rotor is composed of permanent magnets made of highly magnetic materials, possessing a fixed magnetic field polarity.

2. Formation of the Rotating Magnetic Field: The controller energizes each phase winding of the stator sequentially according to a preset logical sequence. For example, energizing phases A, B, and C sequentially creates a magnetic field in a specific direction within the stator each time. By rapidly switching the energized phases, a continuously rotating magnetic field is synthesized in space.

3. Rotor Rotation: Based on the principle of magnetic attraction between opposite poles, the rotating stator magnetic field continuously attracts the magnetic poles of the permanent magnet rotor, causing the rotor to rotate in the direction of the stator magnetic field, thus converting electrical energy into mechanical energy.

4. The Key Role of Electronic Commutation

To ensure continuous rotation, the controller must constantly monitor the rotor's real-time position. This is typically achieved using signals from position detection elements such as Hall effect sensors to precisely determine when and which phase winding should be energized. This process is entirely accomplished by electronic circuitry, replacing the mechanical brushes and commutator structure of traditional brushed motors. This is why it's called electronic commutation, and it's the core reason for the high efficiency, reliability, and long lifespan of brushless motors.