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发电机电刷冒火花与什么原因有关?

来源:http://www.huannengpower.com   发布于:2018-12-11

1、电刷电流密度过大。实际运行中,若果一两个电刷因机械原因卡涩,弹簧压力不足等原因不出力,为维持正常负荷,通过其他电刷的电流就将增大,在增大通流的电刷中如果有被摩偏的电刷,因跟滑环接触面积减小,接触面通流密度增大。根据Q=I*IRT,发热量跟电流的平方成正比,积聚的热量无法散发出去时,温度急剧升高,电刷与滑环接触面就会产生火花。另外火花的产生后,使电刷工作环境更加恶劣,从而恶性循环,使电刷冒火花更严重,几个都有这种情况严重时就会发生环火。
1. Brush current density is too high. In actual operation, if one or two brushes are stuck due to mechanical reasons and spring pressure is insufficient, the current through other brushes will increase in order to maintain normal load. If there is a brush deflected by rubbing in the brush with increasing current, the contact area with the sliding ring will decrease and the current density on the contact surface will increase. According to Q=I*IRT, the calorific value is proportional to the square of the current. When the accumulated calorific value cannot be emitted, the temperature rises sharply and sparks will appear on the contact surface between the brush and the slip ring. In addition, the spark will make the working environment of the brush worse, which will lead to a vicious circle and make the spark of the brush worse. Circumferential fire will occur when several of these conditions are serious.
2、电刷压力不均匀或不符合要求。电刷出厂时厂家都有相关:电刷压力调整到不发生火花的低压力,经过科学论证和实践总结,低压力一般为200~300ɡ/c㎡,即0.02~0.03MPa,要求各个电刷之间的压力也要均匀,其差别不超过10。发电机在长期运行中如果某个电刷摩擦过短,或电刷在刷框内滞卡的情况下,压力将出现不均匀。此外受机械、弹簧本身受热变软等因素影响造成压力达不到电刷不发生火花的低理论要求。还有我们在压紧、提拉碳电刷时,有时靠感觉,没有经验积累,操作误差是很大的。
2. The brush pressure is not uniform or does not meet the requirements. When the brush leaves the factory, the manufacturer is related: the brush pressure is adjusted to the minimum pressure without spark. After scientific demonstration and practice summary, the minimum pressure is generally 200-300/c, that is, 0.02-0.03 MPa. It is required that the pressure between brushes should be uniform, and the difference between brushes should not exceed 10. In the long-term operation of the generator, if the friction of a brush is too short, or when the brush brushes the hysteresis card in the frame, the pressure will be uneven. In addition, due to the influence of machinery and the softening of the spring itself by heat, the pressure can not meet the minimum theoretical requirement that the brush does not spark. In addition, when we press and pull carbon brushes, sometimes we rely on feeling, without experience accumulation, and the operation error is very large.

QQ截图20171025151837.jpg

3、电刷表面不洁。这一点让人忽略的,正常运行的发电机电刷密封在密闭的柜子内,两极电刷中间有套在轴上齿轮状轴流风扇,靠转子转动把磨下的石墨碳粉、电刷的发热及时抽走,达到清洁冷却的作用。如果柜门关不严,或巡检时忘记关门,外面的粉尘伴随着热空气吸进电刷,附着在刷柱上,一方面影响电刷散热。另一方面电刷发生火花时因刷柱表面不洁,刷柱之间绝缘强度不够很容易环火。此外滑环上车有螺旋状一道道沟槽,这是为了增加电刷散热面积,改善同电刷接触,使电刷更充分冷却,同时更容易让碳粉抽走。柜门若关不严,风扇抽力不足外面粉尘也很轻易附着在螺旋状沟里,后果是可想而知的。励磁机电刷考虑其电压等级比较低裸露在外面,在此也建议一下检修定期清洁。前几天我厂发生过励磁电刷冒火花被迫停机事件,原因多方面的,往往小事酿成大祸。我们应该引起足够重视。
3. The surface of the brush is dirty. This is the most neglectable point. Normal generator brushes are sealed in a closed cabinet. There are geared axial flow fans in the middle of the two poles brushes. The heat of graphite powder and brushes is pumped out in time by the rotation of the rotor to achieve the function of clean cooling. If the cabinet door is not closed properly or forgot to close during inspection, the dust outside is absorbed into the brush with hot air and attached to the brush column, which affects the heat dissipation of the brush on the one hand. On the other hand, when sparks occur, the insulation strength between brush columns is not enough because of the unclean surface of brush columns. In addition, there is a spiral groove on the sliding ring, which is to increase the heat dissipation area of the brush, improve the contact with the brush, make the brush more fully cooled, and more easily remove the carbon powder. If the cabinet door is not closed tightly, the fan suction is insufficient outside dust is easily attached to the spiral ditch, the consequences are conceivable. Exciter brushes are exposed because of their low voltage level. It is also recommended that they be cleaned regularly during overhaul. A few days ago, our factory had an excitation brush spark forced shutdown incident, the reasons are various, often small things lead to major disasters. We should pay enough attention to it.
4、轴承振动大。一二期大轴都带励磁机,由于轴承长、带的附加设备多了,振动自然就很难控制到低,。机组长时间运行,疲劳、老化等等复杂因素引起轴承振动加大,电刷随着震动,将使刷柱摩擦不均、引线及弹簧松动,发生局部冒火花慢慢进一步影响全局。
4. Bearing vibration is large. The large axles of the first and second phases are equipped with exciters. Because of the long bearings and many additional equipments, the vibration is naturally difficult to control to the minimum. The vibration of the bearing is increased due to the complex factors such as long running of the unit, fatigue, aging and so on. With the vibration of the brush, the friction of the brush column will be uneven, the lead wire and spring will be loosened, and local sparking will slowly further affect the overall situation.
其他如电刷制造工艺差、研磨不良、电刷位置不对、其隙不均匀、接触电阻过大、负荷高、短路等原因,在实际中可能有,但几年来的生产实践看上述4点的原因居多。
Other reasons, such as poor brush manufacturing technology, poor abrasion, wrong position of brush, uneven gap, excessive contact resistance, high load, short circuit and so on, may exist in practice, but in recent years, the production practice shows that the above four reasons are the most common.
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