Generator brush and excitation electromechanical brush have small resistivity and stable performance, but due to the size of the flow, the pressure of the brush, the surrounding ambient temperature, humidity, cleanliness, wear of the brush and the slip ring surface and itself Due to factors such as manufacturing process, in the long-running operation, if the hidden danger is not found in the first time and the determination process is made decisively, it is inevitable that the flashing of the brush, the ring fire and even the shutdown of the generator due to the brush edge are inevitable. . There are many reasons for the sparking of the brush. The relevant data and procedures have been described in detail. However, there are several reasons for the actual sparking of the brush in actual production:
1. The brush current density is too large. In actual operation, if one or two brushes are stuck due to the mechanical edge, the spring pressure is insufficient, and the current is not increased. In order to maintain the normal load, the current through other brushes will increase, in the case of increasing the flow of the brush. There is a brush that is deflected, and the contact density of the contact surface increases as the contact area with the slip ring decreases. According to Q=I*IRT, the calorific value is proportional to the square of the current, and the accumulated heat cannot be emitted for a while, the temperature rises sharply, and a spark is generated at the contact surface between the brush and the slip ring. In addition, after the generation of the spark, the working environment of the brush is made worse, and the vicious cycle makes the spark spark more serious. When such a serious situation occurs, a ring fire will occur.
2. The brush pressure is not uniform or does not meet the requirements. Power equipment maintenance, manufacturers have a coherent brush when the factory is shipped: the brush pressure is adjusted to the minimum pressure that does not produce sparks. After scientific argumentation and practice summary, the minimum pressure is usually 200 ~ 300 É¡ / cOO, 1.022, 1.03 MPa, requiring each electric The pressure between the brushes should also be uniform, and the difference should not exceed 100. In the case of long-term operation, if a certain brush friction is too short, or the brush is stuck in the brush frame, the pressure will be uneven. In addition, due to the influence of factors such as the heat of the machine and the spring itself, the pressure does not reach the minimum theoretical requirement that the brush does not generate sparks. Also, when we press and pull the carbon brushes, sometimes we rely on the feeling, no experience accumulates, and the manipulation error is very large.
3. The surface of the brush is dirty. This is the most inconspicuous. The normal running generator brush is sealed in a closed cabinet. The two-pole brush has a gear-shaped axial fan on the shaft. The graphite carbon powder and the brush are ground by the rotor. The fever is pumped away in time to reach the role of clean cooling. If the door is not tightly closed, or the door is forgotten when inspecting, the dust outside is sucked into the brush with hot air and attached to the brush column, which affects the heat dissipation of the brush. On the other hand, when the brush generates sparks, the surface of the brush column is unclean, and the strength between the brush columns is not enough, and it is easy to ring fire. In addition, the slip ring has a spiral groove on the car. This is to increase the heat dissipation area of ​​the brush, improve the contact with the brush, make the brush more fully cooled, and make it easier to remove the toner. If the door is not tight, the fan is not enough, and the dust is easily attached to the spiral groove. The consequences are conceivable. The excitation electromechanical brush considers that its voltage level is relatively low and is exposed. It is also recommended to check the regular cleaning. In the first few days, the factory produced over-excitation brush fire, and the generator shutdown event was caused by many aspects, and often small things caused great disaster. We should pay enough attention.
4. The bearing vibration is large. The first and second large shafts are equipped with exciters. Due to the long bearing length and additional equipment, the vibration is naturally difficult to control to the lowest. Long-term operation of the unit, fatigue, aging and other complex factors cause the bearing vibration to increase, the brush will cause the brush column to be unevenly rubbed, the lead wire and the spring loose, and the local spark will gradually further affect the overall situation. Others such as poor brush manufacturing process, poor grinding, incorrect brush position, uneven gap, excessive contact resistance, high load, short circuit, etc. may be in practice, but in the past few years, the production practice seems to be 4 points. The reason is the majority. Since the sparking treatment of the brush is in the coherent data, the procedure has not been specified. Recently, many effective measures have been introduced, which I think are very necessary. Here, I will exchange with you for a few years of experience, and I would like to ask everyone to criticize a lot of corrections.
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