Commutators include: mechanical commutator, semi plastic commutator and full plastic commutator. The commutator used on automobile starter mainly uses mechanical arch commutator and plastic commutator.

The principle is that when the coil passes through the current, it will rotate under the action of the permanent magnet through the attraction and repulsion force. When it turns to balance with the magnet, the contact piece on the corresponding commutator of the originally energized line will be separated from the brush, and the brush will be connected to the contact piece corresponding to the group of coils that generate the driving force. This keeps repeating, and the DC motor will rotate.

If there is no function of commutator, the motor can only be stuck within half a turn, which can only be used as an electric brake. The centrifugal force generated when the motor rotates is used as the power to control the size of the starting resistance, so as to reduce the starting current of the motor, increase the starting torque, and make the wound asynchronous motor realize brushless automatic operation. It is mainly composed of casing, starting fluid, moving electrode plate, spring, terminal, safety valve, exhaust valve, etc. The hydraulic resistance starting device has the characteristics of small starting current, large starting torque, automatic adaptation to changes in power supply and load, motor protection, etc. The commutator is a high-speed rotating equipment, and its rotor winding will be subject to the action of electric force and centrifugal force. Although it has been operating under rated parameters, the welding interface between the rotor winding and the commutator riser is the weak link of the commutator rotor, and the traditional soldering process is used, Based on the measurement results of the DC resistance between the discs, it is judged that the welding point between the rotor winding and the commutator riser is loose, which leads to the fatigue of the end conductor, increases the contact resistance and heat generation, accelerates the oxidation of the contact surface, further increases the contact resistance and heat generation. This vicious cycle leads to the commutator rotor insulation burning at high temperatures, discharging the ground arc, and damaging the commutator. The results of the disassembling inspection of the commutator show that the test data and judgment conclusions of the rotor winding are accurate. In addition to transmitting the longitudinal current, the motor commutator also has the current commutation task in the short-circuit armature coil

These currents are the reverse current and reactance voltage generated when the motor commutator is in the main current, which will cause edge sparks and arcs when the brush slides on the surface of the motor commutator The influence of motor commutator on motor function depends on the process of realizing circuit continuity when it slides with the brush at relatively high speed under certain conditions Although the description of this process is relatively complex and the theoretical research is still developing, through the comparative analysis of the operation conditions of micro motors at home and abroad, it can be determined that wear is the pivotal factor leading to the change of contact resistance.