问题 单项选择题

某生产车间有1台抽风机,生产要求能自起动,抽风机配套的交流异步电动机参数为额定电压6000V,额定功率850kW,额定电流97A,起动电流为额定电流的5.8倍,电动机最大转矩为额定转矩的2.2倍。电网参数:电网电压6000V,在电网最小运行方式下电动机端三相短路时,流过保护的最小三相短路电流为9000A。电动机主回路电流互感器接于相电流,变比为150/5。电动机电源母线电压互感器变比为6000/100。

下列最符合低电压保护的时限为( )s。

A.2.5

B.15

C.0.2

D.7

答案

参考答案:D

完形填空

第二卷(非选择题共35分)

第四部分:写作(共两节,满分35分)

第一节短文填词(共10小题;每小题1分,满分10分)

阅读下面短文,根据以下提示:1)汉语提示,2)首字母提示,3)语境提示,在每个空格内填入一个适当的英语单词,并将该词完整地写在右边相对应的横线上。所填单词要求意义准确,拼写正确。

All of us understand the importance of the eyes. But how to

protect eyesight still       (仍旧是) a question among                      76._____________

(我们)students. If you want to take care of your eyesight,           77._____________

you must pay a     to the following points. Firstly, you                        78._____________

should not use your eyes continuously for long periods.                             79.______________

you have read for a long time, about one hour or so, you t      a          80._____________

rest by        at something more distant. Secondly, you should           81._____________

keep your book about a       (英尺) away from your eyes when          82._____________

you read it. You should also keep in m      , “Don’t read in dim light      83._____________

or      the sun; don’t read in a moving bus or in bed.” Doing                 84._____________

eye exercises regularly will help you keep good eyesight. If you            85._____________

to keep these rules, you will become short-sighted someday.

阅读理解与欣赏