Technical Information Site of Power Supply Design

2021.12.22 motor

Construction of Brushed Motors

Brushed DC Motor

From this article, we explain the constructions, principles of operation, and driving methods of various types of motor. We begin with brushed motors.

Construction of Brushed Motors

Below are shown external views of a brushed DC motor that is often used in models and the like, as well as the disassembled parts of a general two-pole (two magnets), three-slot (three coils) type motor. Many readers will likely have at one time or another disassembled a motor and looked at the magnets or other parts.

The permanent magnets are fixed in place, and the coils at the center of the interior can rotate. The immobilized part is called the stator, and the rotating part is called the rotor.

Below are summary diagrams conceptually illustrating the construction.

There are three commutators (curved metal pieces for current switching) about the shaft, which is the center of rotation. The commutators are arranged at every 120° (360°/3) in such a way that they do not make mutual contact. The commutators rotate together with rotation of the shaft.

Each commutator is connected to an end of one coil and an end of another coil, and the three commutators and three coils form a ring-shaped network (see "Commutator and coil connection equivalent circuit").

Two brushes (see "Summary diagram of the internal construction of a brushed motor") are fixed at 0° and 180° positions so as to make contact with the commutators. The brushes are connected to an external DC power supply, and current flows in the path brush → commutator → coil → brush.

Key Points:

・As their name implies, brushed motors have special electrodes called brushes.

・Their construction consists of a stator and a rotor; the stator includes magnets, and the rotor includes coils and commutators.

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