DC motor is a rotating motor that can convert DC electric energy into mechanical energy (DC motor) or mechanical energy into DC electric energy (DC generator). It is a motor that can convert DC electric energy and mechanical energy to each other. When it runs as a motor, it is a DC motor, which converts electrical energy into mechanical energy; when it runs as a generator, it is a DC generator, which converts mechanical energy into electrical energy. A DC generator is a machine that converts mechanical energy into DC electrical energy. It is mainly used as a DC motor required for DC motors, electrolysis, electroplating, electric smelting, charging, and excitation power for AC generators. Although power rectification components are also used where DC power is needed to convert AC power into DC power, AC rectifier power cannot completely replace DC generators in terms of certain work performance. DC motor:A rotating device that converts DC electrical energy into mechanical energy. The stator of the motor provides the magnetic field, the DC power supply provides the current to the windings of the rotor, and the commutator keeps the rotor current in the same direction as the torque generated by the magnetic field. DC motors can be divided into two categories, including brush DC motors and brushless DC motors, depending on whether they are equipped with a common brush-commutator or not. Brushless DC motor: It is a new type of DC motor developed in recent years with the development of microprocessor technology and the application of new power electronic devices with high switching frequency and low power consumption, as well as the optimization of control methods and the emergence of low-cost, high magnetic energy level permanent magnet materials. Brushless DC motor not only maintains the good speed regulation performance of traditional DC motor but also has the advantages of no sliding contact and commutation spark, high reliability, long service life and low noise, etc. Therefore, it has been widely used in aerospace, CNC machine tools, robots, electric vehicles, computer peripherals and household appliances. According to the different power supply methods, brushless DC motors can be divided into two categories: square wave brushless DC motors, whose counter potential waveform and supply current waveform are rectangular waveform, also known as rectangular waveform permanent magnet synchronous motor; sine wave brushless DC motors, whose counter potential waveform and supply current waveform are sine waveform.