电动机定子线圈绝缘损坏的原因有哪些？
参考答案：
电动机定子线圈绝缘损坏的原因有：
（1）经常超负荷运行，绕组经常过热，绝缘因受热老化；
（2）制造工艺不良或槽楔打得不紧，使线圈在槽内松动，或端部绑扎不牢，绝缘层受损；
（3）电动机使用日久，绝缘老化；
（4）电动机受潮或受腐蚀，绝缘值降低；
（5）铁屑、焊渣等铁磁物质落入线圈表面或槽壁，在交变磁场的作用下产生振动，使线圈绝缘层被磨损；
（6）电动机扫膛，槽温升高，使槽内线圈绝缘迅速老化。
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| Ever since Jonathan had set up the house in Compton Street, he had looked after it very carefully. Before he left the house in the morning, he carefully closed all the __1__ downstairs, opened some windows to let the air in and locked the front gate. __2__ Jonathan did was tidy and orderly. One summer evening Jonathan returned home __3__ at five to seven exactly. When he opened the front gate, he immediately noticed something strange. There was a heavy footprint (脚印) in the earth in one of the flower beds. Jonathan was just going to blame (责怪) the milkman or the postman __4__ he noticed that one of the curtains (窗帘) in the front room downstairs was out of place. Jonathan never left anything out of place. He walked up to the front door and opened it quietly. He listened carefully for a few moments, but could hear nothing. The front-room door was half-open. Jonathan studied it carefully, __5__ if he had forgotten to close it that morning. He had never forgotten before. He stepped silently across the hall to the door and looked __6__ the room. The shadow (影子) of a man was clearly reflected on (映在) the far __7__ in the evening sunlight. He had been standing behind the door since Jonathan returned. Jonathan grabbed the door-handle (抓住门把手), __8__ the door quickly and turned the key. Then he __9__ the telephone in the hall and set about calling the police. The thief (小偷) tried to climb through a window to get out, but Jonathan had __10__ that. He attacked him with his umbrella, __11__ it as a sword (剑). Three minutes later the __12__ arrived there. Jonathan was a little angry that he had to have dinner later than usual, but on the whole he felt quite pleased with himself. | ||||
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