Motor (English: Electric machinery, commonly known as "motor") refers to an electromagnetic device that realizes electric energy conversion or transmission according to the law of electromagnetic induction. The motor is represented by the letter M (old mark D) in the circuit, and its main function is to generate driving torque. As the power source of electrical appliances or various machines, the generator is represented by the letter G in the circuit, and its main function is to convert electrical energy into mechanical energy.
Brushless DC motor uses semiconductor switching devices to realize electronic commutation, that is, electronic switching devices replace traditional contact commutator and brush. It has the advantages of high reliability, no commutation spark and low mechanical noise, and is widely used in high-end recording studios, video recorders, electronic instruments and automatic office equipment.