What are the reasons why the oxide film of the commutator brush cannot be formed

Update:25 Oct 2021

Strengthen the understanding of the oxide film on the surface of the brush, and create the conditions for its formation and normal operation. If the oxide film lubricating layer on the surface of the brush cannot be formed, it means that some conditions for forming the oxide film are not met. To sum up, the oxide film cannot be formed or formed poorly due to the following reasons:
(1) The temperature is too high: the oxide film of the brush is generally easy to form at about 70 degrees Celsius. When the commutator or the brush has an overheating failure, the temperature is usually above 150 degrees Celsius. Brush, oxide film is not easy to form, can not play a role in lubrication, brush wear will increase, resulting in continued temperature rise, forming a vicious circle. At this time, an external forced cooling method can be used, such as applying petroleum jelly, high-power fan ventilation, etc., to reduce the commutator temperature to the normal range. After a period of time, the oxide film on the brush surface will gradually form, making it enter a virtuous cycle state.
(2) Polluting impurities in the cooling air: The impurities in the air will have an adverse effect on the formation of the oxide film on the surface of the brush. These impurities include corrosive gases such as sulfides, oil and gas mixtures in the air, dust and other impurities. When the brush is worn, it will produce dust and impurities of carbon powder. The air quality in the brush holder cover can be used.
(3) The air humidity is too low or the oxygen content is too low. The formation of the oxide film on the surface of the brush requires a certain amount of moisture in the air, that is, the air humidity cannot be too low, but not too high.

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