The motor commutator is a component of a DC permanent magnet series motor in order to allow the motor to continue to rotate. In structure, the motor commutator is a circle of several contact pieces, which are connected to each contact on the rotor, respectively. The two electrodes connected on the outside are called brushes, and only two of them are contacted at the same time. The principle of the motor commutator is that when the coil passes the current, it will rotate under the action of the permanent magnet by the attraction and repulsion force. When it is turned to balance with the magnet, the original line of electricity is separated from the brushes of the corresponding motor commutator, and the brush is connected to the corresponding contact of the set of coils that generate the driving force. Repeat this way, and the DC motor will turn.
The commutation of a DC motor commutator refers to the rotating armature winding element. Generally, sparks must be generated between the brush and the commutator, the main reason for the difficulty in commutation and the failure. Therefore, the national code according to the commutation of the motor When the size of the spark is divided into several levels (1,5 / 4,3 / 2,2,3). For continuous working DC motors, the commutation spark should not exceed 3/2 levels. DC motors for electric bicycles belong to Continuously operated motors should meet the requirements of no more than 3/2 grade sparks. The specification states that when 3/2 grade sparks, most or all of the brush edges have weak sparks, so black marks appear on the commutator, but It will not continue to develop.It can be removed by rubbing its surface with gasoline.At the same time, there are slight burn marks on the brushes, which will not affect the continuous normal operation of the motor.
The motor commutator and the brush constitute a corresponding sliding friction pair in the motor. The effect of the motor commutator on the motor performance mainly depends on the high-speed sliding of the brush under certain conditions (electric load, contact pressure, environmental conditions, etc.) Electrical contact behavior. In addition to transmitting longitudinal current during the operation of the motor commutator, there is also a current commutation task performed in the short-circuit armature coil. These currents are the reverse current generated when the commutator of the main current motor And reactance voltage, causing the brush to cause sparks and arcs on the edges when the brush slides on the surface of the motor commutator.
In the commutating element, reactance potential and commutation potential occur during commutation. The sum of these potentials is generally greater than zero, which is called delayed commutation. When the commutator brushes away from one commutator and turns to another adjacent commutator When the commutation current is not zero, electromagnetic energy is stored in the commutation element. When the previous commutator leaves the brush, the commutation circuit is suddenly cut off, and the electromagnetic energy in the commutation element is only released by breaking through the air. And sparks occur.