Permanent magnet DC motor is a DC motor which uses permanent magnets to establish magnetic field. Permanent magnet DC motors are widely used in various portable electronic devices or appliances, such as tape recorders, VCD players, record players, electric massagers and various toys, as well as automobiles, motorcycles, electric bicycles, battery cars, ships, aviation, machinery and other industries. They are also widely used in some high-tech products, such as video recorders, photocopiers, cameras, mobile phones, precision machine tools, bank money counters, money binding machines and so on.