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DC permanent magnet motor commutator is on the series motor in order to enable the motor to go on a continuous rotating parts. Structure, the motor commutator contact pads surrounded by a few round, on the rotor are connected to each contact, connected to two electrodes as outside contact with brush, while only contacted two of the motor's commutator theory is that when the current through the coil, will the role of the permanent magnet, through the attraction and repulsion rotation , and the magnet when it is to balance the original through a power line than the corresponding contacts on the motor commutator and electric Shuafen on leave, and brush generated connected to the driving force of the group in line with the corresponding contacts on the coil This kept repeating down the DC motor to turn up.
DC motor commutation commutator is rotating armature winding element, normally in between brush and commutator to produce sparks for the difficulties and the main reason for failure, so the national standard for the motor commutation when the spark size will be divided into several levels (1,5 / 4,3 / 2,2,3). DC motor for continuous operation, the commutation spark should not exceed 3 / 2. DC motor for electric bicycle are continuous operation of the motor, should meet no more than 3 / 2 spark requirements. specification: 3 / 2 sparks, brush the edges of most or all of the weak spark, so there are black marks appear on the commutator, but will not continue to develop, rub the surface with a gasoline that can be removed, while there is a slight burning brush marks, which will not affect the motor continuously running.
Motor commutator and brushes in the motor component corresponding to the sliding friction, the motor commutator motor performance depends on certain conditions (electrical load, contact pressure, environmental conditions, etc.) relative to high-speed sliding brush electrical contact to the motor commutator vertical transmission in addition to current work, but there are still carried out in the short-circuit current in the armature coil to task for these currents are in the main current of the motor commutator and sometimes reverse current generated and the reactance voltage, resulting in the motor brush commutator slide surface edge will cause sparks and electric arc.
Change will happen to the components in the electrical potential and resistance to potential change, when change to these potential generally greater than the sum of zero, said commutation delay when the left side of the commutator brush after a change to another piece adjacent to the commutation films, for the current is not zero, there is electromagnetic energy stored in the commutation components, the first to leave a commutator brushes, the commutation circuit is suddenly cut off, for the components of the electromagnetic energy to breakdown the air and release only , thus sparking.
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