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發電機電刷冒火花與什么原因有關?

來源:http://dgxcbw.com   發布于:2018-12-11

1、電刷電流密度過大。實際運行中,若果一兩個電刷因機械原因卡澀,彈簧壓力不足等原因不出力,為維持正常負荷,通過其他電刷的電流就將增大,在增大通流的電刷中如果有被摩偏的電刷,因跟滑環接觸面積減小,接觸面通流密度增大。根據Q=I*IRT,發熱量跟電流的平方成正比,積聚的熱量無法散發出去時,溫度急劇升高,電刷與滑環接觸面就會產生火花。另外火花的產生后,使電刷工作環境更加惡劣,從而惡性循環,使電刷冒火花更嚴重,幾個都有這種情況嚴重時就會發生環火。
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、電刷壓力不均勻或不符合要求。電刷出廠時廠家都有相關:電刷壓力調整到不發生火花的低壓力,經過科學論證和實踐總結,低壓力一般為200~300ɡ/c㎡,即0.02~0.03MPa,要求各個電刷之間的壓力也要均勻,其差別不超過10。發電機在長期運行中如果某個電刷摩擦過短,或電刷在刷框內滯卡的情況下,壓力將出現不均勻。此外受機械、彈簧本身受熱變軟等因素影響造成壓力達不到電刷不發生火花的低理論要求。還有我們在壓緊、提拉碳電刷時,有時靠感覺,沒有經驗積累,操作誤差是很大的。
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.

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3、電刷表面不潔。這一點讓人忽略的,正常運行的發電機電刷密封在密閉的柜子內,兩極電刷中間有套在軸上齒輪狀軸流風扇,靠轉子轉動把磨下的石墨碳粉、電刷的發熱及時抽走,達到清潔冷卻的作用。如果柜門關不嚴,或巡檢時忘記關門,外面的粉塵伴隨著熱空氣吸進電刷,附著在刷柱上,一方面影響電刷散熱。另一方面電刷發生火花時因刷柱表面不潔,刷柱之間絕緣強度不夠很容易環火。此外滑環上車有螺旋狀一道道溝槽,這是為了增加電刷散熱面積,改善同電刷接觸,使電刷更充分冷卻,同時更容易讓碳粉抽走。柜門若關不嚴,風扇抽力不足外面粉塵也很輕易附著在螺旋狀溝里,后果是可想而知的。勵磁機電刷考慮其電壓等級比較低裸露在外面,在此也建議一下檢修定期清潔。前幾天我廠發生過勵磁電刷冒火花被迫停機事件,原因多方面的,往往小事釀成大禍。我們應該引起足夠重視。
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、軸承振動大。一二期大軸都帶勵磁機,由于軸承長、帶的附加設備多了,振動自然就很難控制到低,。機組長時間運行,疲勞、老化等等復雜因素引起軸承振動加大,電刷隨著震動,將使刷柱摩擦不均、引線及彈簧松動,發生局部冒火花慢慢進一步影響全局。
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.
其他如電刷制造工藝差、研磨不良、電刷位置不對、其隙不均勻、接觸電阻過大、負荷高、短路等原因,在實際中可能有,但幾年來的生產實踐看上述4點的原因居多。
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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