题目内容
直流电动机反接制动时，当电动机转速接近于零时，就应立即切断电源，防止动机过载。
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直流电机的电刷因磨损而需更换时应选用与原电刷相同的电刷。
直流电动机的电磁转矩在电动状态时是驱动性质的转矩，当增大电磁转矩电动机的转速将会上升。
直流电机中，换向极的作用是改变换向，所以只要装置换向极都能起到改向的作用。
The justification for a university is that it preserves the connection between knowledge and the zest of life, by___1____ the young and the old in the imaginative consideration of learning. The university imparts information, but it imparts it imaginatively. At least, this is the____2___which it should perform for society. A university which fails in this respect has no reason for ___3____ .
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