Factors causing the heating of carbon brush 1. The dispersion of carbon brush resistance increases, which increases the heating of carbon brush resistance. 2, carbon card resistance. When the carbon brush is electrified, the brush body expands and easily gets stuck in the brush grip. Part of the carbon brush due to vibration, brush grip is not vertical and other reasons, the brush grip on one side of the upper edge and the other side of the lower edge will produce obvious blocking, these forms of resistance, with the clamp table can still be measured current, easy to be misleading. At this point, the carbon brush has failed, resulting in increased current distribution of other carbon brushes and increased heat. 3. Carbon brush pressure decreases. Although the constant pressure brush grip, but there are differences in the spring pressure. The pressure is small to a certain extent, the contact is unstable, the contact pressure drop increases, and the fever increases obviously. At the same time, due to the insufficient spring pressure, the extension of the contact surface between the brush and the carbon brush increases the side friction resistance of the carbon brush, and the carbon brush is blocked in the grip. 4. Carbon brush contact surface forms an air film. The carbon brush runs at the maximum allowable speed, and it is easy to generate gas film and pulsation on the contact surface. The current flowing through the carbon brush is unstable. Grooves and larger grinding are made on the surface of the slip ring. But the actual contact area of the brush is reduced by grooving. The slip-ring oxidation film is too thick, the contact resistance of the carbon brush increases, and the excitation current shunt to the carbon brush with low resistance in other circuits. 6. Destruction of current balance. Generally, the contact force between the carbon brush and the slip ring is relatively large, and the contact pressure drop is small. All carbon brushes work in similar conditions, and the current of each carbon brush is nearly equal. The average temperature of the brush body is relatively low, and the current between carbon brushes is relatively stable and balanced. After running for a period of time, oxidation film, gas film, long resistance and other factors appear, carbon brush grinding short or spring pressure decreases, carbon brush contact surface contact force decreases, carbon brush current redistribution, each carbon brush current difference increases and in an unstable balance. This stage is long, gradual and difficult to detect. When the ambient temperature increases or the excitation current increases, the balance can be destroyed at any time.

Heat treatment 1, when the fever in the early, the heating temperature is not higher than 100 ° C, can adopt the method of adjusting part of the working poor carbon brush. Such as replacement wear, working current is small carbon brush; Adjust or replace part of the less elastic brush spring to optimize current distribution. 2. Appropriately reduce the reactive load of the generator, reduce the excitation current, reduce the working current of the carbon brush, and reduce heat. 3. When the braid is broken by individual carbon brushes, the excitation current can be reduced first; In case of ring fire, the excitation current is greatly reduced, and the carbon brush shall be replaced after adjusting the current balance of carbon brush. A large number of carbon brushes cannot be replaced forcibly. 4. Clean the vents and keep the air passage clear.

Fever of emergency response when the temperature is above 120 ° C to replace carbon brush or adjust the brush holder has not reduce the overall temperature, due to the new change of carbon brush and slip ring giant is not smooth, less contact area, no matter how much the distribution of electric current conduction of heat will make its temperature rise. At this time the most important measure is to reduce the working temperature, improve the working condition of the carbon brush, brush grip. In normal operation, the working current and the ambient temperature do not change much, while the carbon brush temperature rises seriously, which may be caused by a small number of carbon brush faults (such as increased resistance, reduced spring pressure, carbon brush length and acerbity, carbon brush braids). At this time, the carbon brush causing heat should be accurately determined and removed to make other carbon brushes work normally and enter the normal equilibrium state. The key to this approach is to make an accurate judgment, the failure of the carbon brush generally manifested as vibration, large current, sometimes its temperature is higher than the overall temperature. If it is not possible to make an accurate judgment, a brush holder can be taken out in turn every once in a while by using the test method, until the overall temperature drops significantly. After the system temperature returns to normal, the treated carbon brush will be reinstalled.