Introduction to the structure of brushless motor

Starting from this article, we will introduce the structure, working principle and driving method of various motors. The first is the brushless motor.

The structure of a brushless motor

Below is the appearance of a brushed DC motor that is often used in models, as well as an exploded diagram of a common two-pole (2 magnets) three-slot (3 coils) type motor. Perhaps many people have the experience of disassembling a motor and taking out the magnets.

You can see that the permanent magnet of the brushed DC motor is fixed, and the coil of the brushed DC motor can rotate around the internal center. The fixed side is called the "stator" and the rotating side is called the "rotor".

Below is a simplified structural diagram representing the structural concept.

There are three commutators (bent metal pieces used to switch current) around the outer periphery of the rotating central shaft. To avoid contact with each other, the commutators are arranged 120° apart (360°÷3 pieces). The commutators rotate as the shaft rotates.

One commutator is connected with one coil end and the other coil end, and three commutators and three coils form a whole (ring) as a circuit network (see "Commutator and coil connection equivalent circuit").

The two brushes (see "Brushed Motor Internal Structure Diagram") are fixed at 0° and 180° to contact the commutator. An external DC power supply is connected to the brushes, and the current flows along the path of brush → commutator → coil → brush.

Key Takeaways:

・As the name suggests, brushed motors have electrodes called "brushes".

・A brushed motor consists of a stator and a rotor. The stator of a brushed motor includes magnets, and the rotor includes coils and a commutator.