導(dǎo)致發(fā)電機(jī)組碳刷故障的因素

　　電磁因素：無(wú)功或勵(lì)磁電流調(diào)整時(shí)，碳刷的火花有明顯變化。在勵(lì)磁機(jī)換向時(shí)，碳刷與換向片接觸不良，接觸電阻過(guò)大；整流子或滑環(huán)的氧化膜薄厚不均勻，引起碳刷電流分布不平衡；或者負(fù)載突然變化，以及突發(fā)的短路導(dǎo)致?lián)Q向片間的電壓分布異常；機(jī)組過(guò)載和不平衡；碳刷選型不合理，碳刷間距不等；碳刷質(zhì)量問(wèn)題等等。

　　機(jī)械因素：換向器中心不正，轉(zhuǎn)子不平衡；機(jī)組振動(dòng)大；換向片間絕緣凸出或換向片凸出；碳刷接觸面研磨不光滑，或換向器表面粗糙而造成接觸不良；換向器表面不清潔；各個(gè)換向極下氣隙不等；碳刷上彈簧壓力不均勻或大小不適宜；碳刷在刷握里太松而發(fā)生跳動(dòng)，或太緊了碳刷在刷握里卡住了等。機(jī)組運(yùn)轉(zhuǎn)速度降低或震動(dòng)改善，火花將減少。

　　化學(xué)因素：發(fā)電機(jī)組運(yùn)行在有腐蝕性的氣體中，或機(jī)組運(yùn)行空間缺乏氧氣，換向器與碳刷接觸的表面上一層自然形成銅氧化物薄膜遭到破壞，本已形成的、近似線性電阻的換向不復(fù)存在，在接觸面重新形成氧化膜的過(guò)程中換向器火花加劇。換向器（或滑環(huán)）被酸性氣體或油脂腐蝕。碳刷及換向器被污染等。

柴油發(fā)電機(jī)組碳刷的維護(hù)

　　A、運(yùn)行檢查：加強(qiáng)定期與不定期的設(shè)備巡回檢查工作，正常情況下,工作人員每天必須對(duì)發(fā)電機(jī)碳刷進(jìn)行兩次檢查（上午一次，下午一次），用紅外測(cè)溫儀測(cè)量集電環(huán)和碳刷的溫度，夏季高峰負(fù)荷期間以及無(wú)功和電壓波動(dòng)較大時(shí)應(yīng)縮短溫度測(cè)量間隔，更換的新碳刷做重點(diǎn)檢查。有條件的單位應(yīng)定期用紅外熱像儀測(cè)量集電環(huán)和碳刷的溫度。并做好巡回檢查設(shè)備運(yùn)行工況記錄。

　　B、檢修更換：對(duì)新購(gòu)進(jìn)的碳刷進(jìn)行驗(yàn)收。測(cè)定碳刷的固有電阻值，測(cè)量碳刷引線接觸電阻，阻值要符合制造廠和國(guó)家標(biāo)準(zhǔn)。嚴(yán)格把握更換碳刷工藝，同一臺(tái)機(jī)組使用的碳刷必須一致，不可摻插使用。在更換碳刷前，細(xì)心研磨碳刷使其面面光滑，電刷在刷握內(nèi)應(yīng)有0.2 0.4毫米的間隙，在刷握內(nèi)上下活動(dòng)自如。刷握的下邊緣和換向器工作表面之間的距離為2-3毫米，距離過(guò)小，會(huì)碰撞換向器表面，易受損、距離過(guò)大電刷跳動(dòng)易產(chǎn)生火花。爭(zhēng)取實(shí)現(xiàn)碳刷接觸面大于碳刷截面的80％。勤更換，但多次更換碳刷不宜過(guò)多，一次更換碳刷的數(shù)量不得超過(guò)單極總數(shù)的10％，碳刷頂端低于刷握頂端3mm的碳刷應(yīng)盡快更換，每次更換碳刷時(shí)必須使用同一型號(hào)的碳刷，但要注意節(jié)約和充分利用碳刷。更換后的碳刷必須用直流卡鉗表測(cè)量碳刷分流情況，用紅外測(cè)溫儀進(jìn)行溫度測(cè)試，防止個(gè)別碳刷因過(guò)流而過(guò)熱。對(duì)于滑環(huán)或整流子換向片凸起與凹陷等明顯設(shè)備問(wèn)題，要利用機(jī)組檢修的機(jī)會(huì)進(jìn)行緊固、車(chē)磨。加強(qiáng)檢修質(zhì)量和運(yùn)行控制，避免由于檢修質(zhì)量不良或運(yùn)行調(diào)整不當(dāng)造成機(jī)組運(yùn)行中，汽輪機(jī)油外泄，甩到集電環(huán)上，增大碳刷與集電環(huán)之間的接觸電阻。刷架和刷握在機(jī)組大、小修時(shí)要慎重調(diào)整，回放和安裝刷架時(shí)，角度和幾何位置要保證在原狀態(tài)，碳刷的滑入邊和滑出邊必須要與換向器平行。

　　C、日常維護(hù)：勤清掃、吹灰，保持碳刷及整流子滑環(huán)光面清潔，若遇大風(fēng)天氣，或過(guò)后必須及時(shí)清掃。勤調(diào)整彈簧壓力，碳刷彈簧的壓力要符合制造廠家的規(guī)定，使碳刷承受壓力均勻。防止個(gè)別碳刷過(guò)熱或產(chǎn)生火花、刷辮燒焦燒斷現(xiàn)象的發(fā)生。碳刷運(yùn)行中出現(xiàn)問(wèn)題必須及時(shí)消缺，避免惡性循環(huán)，危及機(jī)組正常運(yùn)行。同一臺(tái)機(jī)組使用的碳刷必須一致，不可摻插使用。進(jìn)行維護(hù)的工作人員，檢查維護(hù)時(shí)要特別小心，發(fā)辮應(yīng)放在帽內(nèi)、扣緊袖口，不使衣服及擦拭材料被機(jī)器掛住。工作時(shí)站在絕緣墊上，不得同時(shí)接觸兩極或一極與接地部份，也不能兩個(gè)人同時(shí)進(jìn)行工作。在轉(zhuǎn)動(dòng)著的電機(jī)上調(diào)整、清掃碳刷及滑環(huán)時(shí)，須有實(shí)踐經(jīng)驗(yàn)的同志進(jìn)行。

Factors causing carbon brush failure in generator sets

Electromagnetic factors: When reactive power or excitation current is adjusted, there is a significant change in the spark of the carbon brush. During the commutation of the exciter, the contact between the carbon brush and the commutator is poor, resulting in excessive contact resistance; The uneven thickness of the oxide film on the rectifier or slip ring causes an unbalanced distribution of carbon brush current; Or sudden changes in load, as well as sudden short circuits causing abnormal voltage distribution between commutator segments; Unit overload and imbalance; Unreasonable selection of carbon brushes, unequal spacing between carbon brushes; Quality issues with carbon brushes, etc.

Mechanical factors: Misalignment of commutator center and rotor imbalance; The unit experiences significant vibration; Insulation protrusion between commutator segments or protrusion of commutator segments; Poor contact caused by uneven grinding of the carbon brush contact surface or rough surface of the commutator; The surface of the commutator is not clean; The air gap under each reversing pole is uneven; Uneven or inappropriate spring pressure on the carbon brush; The carbon brush is too loose in the brush holder and jumps, or it is too tight and gets stuck in the brush holder. If the operating speed of the unit decreases or the vibration improves, sparks will decrease.

Chemical factors: When the unit operates in corrosive gases or when there is a lack of oxygen in the operating space, the naturally formed copper oxide film on the surface of the commutator in contact with the carbon brush is damaged, and the already formed, approximately linear resistance commutation no longer exists. During the process of re forming an oxide film on the contact surface, sparks from the commutator intensify. The commutator (or slip ring) is corroded by acidic gases or grease. Carbon brushes and commutators are contaminated, etc.

Maintenance of Carbon Brushes in Diesel Generator Sets

A. Operation inspection: Strengthen regular and irregular equipment patrol inspection work. Under normal circumstances, staff must inspect the generator carbon brush twice a day (once in the morning and once in the afternoon), measure the temperature of the collector ring and carbon brush with an infrared thermometer. During peak load periods in summer and when there are large fluctuations in reactive power and voltage, the temperature measurement interval should be shortened, and the replacement of new carbon brushes should be checked with emphasis. Conditional units should regularly use infrared thermal imagers to measure the temperature of the collector ring and carbon brush. And keep a record of the operating conditions of the equipment during the patrol inspection.

B. Maintenance and replacement: Conduct acceptance inspection on newly purchased carbon brushes. Measure the inherent resistance value of the carbon brush, measure the contact resistance of the carbon brush lead, and ensure that the resistance value meets the manufacturer's and national standards. Strictly adhere to the process of replacing carbon brushes, and the carbon brushes used in the same unit must be consistent and cannot be used interchangeably. Before replacing the carbon brush, carefully grind the carbon brush to make its surface smooth. The brush should have a gap of 0.2 and 0.4 millimeters in the brush holder and move freely up and down inside the brush holder. The distance between the lower edge of the brush holder and the working surface of the commutator is 2-3 millimeters. If the distance is too small, it will collide with the commutator surface, which is prone to damage. If the distance is too large, the electric brush will jump and spark. Strive to achieve a carbon brush contact surface greater than 80% of the carbon brush cross-section. Replace frequently, but do not replace too many carbon brushes multiple times. The number of carbon brushes to be replaced at once should not exceed 10% of the total number of single poles. Carbon brushes with a top 3mm lower than the top of the brush holder should be replaced as soon as possible. The same type of carbon brush must be used each time the carbon brush is replaced, but attention should be paid to saving and fully utilizing the carbon brush. The replaced carbon brush must be measured for carbon brush current distribution using a DC caliper gauge and temperature tested using an infrared thermometer to prevent individual carbon brushes from overheating due to overcurrent. For obvious equipment problems such as protrusions and indentations on slip rings or commutator segments, it is necessary to use the opportunity of unit maintenance to tighten and grind them. Strengthen the quality of maintenance and operation control to avoid the leakage of turbine oil during unit operation due to poor maintenance quality or improper operation adjustment, which can be thrown onto the collector ring and increase the contact resistance between the carbon brush and the collector ring. The brush holder and brush holder should be carefully adjusted during major and minor repairs of the unit. When replaying and installing the brush holder, the angle and geometric position should be ensured to be in their original state. The sliding edge and sliding edge of the carbon brush must be parallel to the commutator.

C. Daily maintenance: Clean and blow dust frequently, keep the carbon brush and commutator slip ring clean, and clean them promptly in case of strong winds or after. Adjust the spring pressure frequently, and ensure that the pressure of the carbon brush spring meets the manufacturer's specifications, so that the carbon brush can withstand pressure evenly. Prevent individual carbon brushes from overheating or generating sparks, and prevent the occurrence of burnt or broken bristles. Any problems that arise during the operation of carbon brushes must be promptly resolved to avoid a vicious cycle that could jeopardize the normal operation of the unit. The carbon brushes used in the same unit must be consistent and cannot be used interchangeably. The maintenance personnel should be particularly careful during inspection and maintenance. The braids should be placed inside the hat, the cuffs should be fastened, and clothes and wiping materials should not be hung by the machine. When working, stand on an insulation pad and do not touch both poles or one pole and the grounding part at the same time, nor can two people work at the same time. When adjusting and cleaning carbon brushes and slip rings on a rotating motor, comrades with practical experience are required.