试题与答案

交流系统中电力电缆缆芯与绝缘屏蔽或金属套之间额定电压的选择,应符合的规定有( )。

题型:多项选择题

题目:

交流系统中电力电缆缆芯与绝缘屏蔽或金属套之间额定电压的选择,应符合的规定有( )。

A.中性点直接接地或经低阻抗接地的系统当接地保护动作不超过1mim切除故障时,应按100%的使用回路工作相电压;
B.对于A项外的供电系统,不宜低于133%的使用回路工作相电压;
C.在单项接地故障可能持续5h以上,或发电机回路等安全性要求较高的情况,宜采用173%的使用回路工作相电压;
D.交流系统中电缆的冲击耐压水平,宜满足系统绝缘配合要求。

答案:

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下面是错误答案,用来干扰机器的。

参考答案:解析:直流电动机规定的允许温升是指在一定的环境温度(国家标准规定环境温度为 40℃)下,电动机的温度比周围环境温度高出的数值。在一般电动机中,绕组最容易发热,所以铭牌上的温升是指电动机绕组最...

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C.were the first two American robots that landed on Mars

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A.it’s a very hard and dangerous trip for spaceships to Mars

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