Basic knowledge of PMDC motor


This article describes the history, principle, basic structure, and application of the PMDC motor (Permanent Magnet Direct Current Motor ).

The history of PMDC motor can be chased down to more than 100 years ago. It has always existed in various electrical appliances in people’s lives. It has the advantages of simple control, high starting torque, low-temperature rise, and low cost.

PMDC motor

PMDC brush motoris an electromagnetic device that realizes the conversion or transfer of electric energy according to the law of electromagnetic induction. It is represented by the letter “M” in the circuit (the old standard is “D”).

The DC motor is made according to the principle that the current-carrying conductor will be subjected to the action of electromagnetic force in the magnetic field. Energy conversion is to convert electrical energy into mechanical energy, and can also convert mechanical energy into electrical energy (eg. a hand-cranked generator); its main function is to generate driving torque as a power source for electrical appliances or various machinery.

In the category of Kinmore PMDC motors, there is also a type of electromagnetic brushed DC motor. The difference is that the former is the main magnetic field generated by the permanent magnet, while the latter is the main magnetic field generated by the electromagnetic winding.

PMDC motor basic

The basic structure of the motor, and the basic structural components of the permanent magnet brushed DC motor are: the stator, rotor, brushes, and commutator. The stator also contains end caps, and the rest of the article goes into more detail about the structure of each component.


The stator generates a fixed magnetic field around the rotor. This magnetic field can be generated by permanent magnets or electromagnetic windings. The types of brushed DC motors are divided by the structure of the stator or the way the electromagnetic windings are connected to the power supply. At present, the brushed DC motors of Kinmore are all using permanent magnet stators.


The rotor (also called the armature) consists of one or more windings. When these windings are energized, a magnetic field is created. The poles of the rotor field will attract the opposite poles of the stator field, causing the rotor to rotate.

As the motor rotates, the windings are continuously energized in a different order, so the poles produced by the rotor never overlap those produced by the stator. This switching of the magnetic field in the rotor winding is called commutation.

Brushes (carbon brushes) and commutators

Brushed DC motor control is relatively simple, it does not require a controller to switch the direction of the current in the electrode windings, but mechanically completes the commutation of the brushed DC motor windings. A segmented device, called a commutator, is mounted on the shaft of a brushed DC motor.

The permanent magnet DC brush motor, one of the main products of Kinmore, is currently widely used in various electronic equipment or appliances, such as coffee machines, vacuum cleaners, hair dryers, smart door locks, smart water meters, HVAC valves, electric massagers and various Toys are also widely used in automobiles, motorcycles, electric bicycles, battery vehicles, ships, aviation, machinery and other industries, and are also widely used in some high-precision products, such as medical equipment, video recorders, copiers, cameras, mobile phones, precision machine tools , bank money counting machine, banknote machine and so on.


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