问题 问答题 简答题

什么是强励峰值电压倍数和励磁电压上升速度?

答案

参考答案:

强励峰值电压倍数是指在同步发电机事故情况下,励磁系统强行励磁时的励磁电压和额定历次电压之比,此值可根据机组和电网的运行要求而定。一般对于空气冷却励磁绕组的汽轮发电机,强励电压为2倍额定励磁电压,强励允许时间为50s;对于水冷和氢冷励磁绕组的汽轮发电机,强励电压为2倍额定励磁电压,强励允许时间为10~20s。

励磁电压上升速度是指励磁电压在强励发生后最初半秒钟内由正常电压开始的上升速度,常用1s内升高的励磁电压对额定励磁电压的倍数来表示,此值一般要求在0.8~1.2之间,即1s内励磁电压升高80%~120%。

完形填空

阅读短文,根据要求完成下面各小题。

Wang Ruonan is a 17-year-old Beijinger. Huang Yuying is a Junior 1 middle school student living in Beichuan, Sichuan. The two girls are good friends. Their friendship started from a schoolbag.

In 2009 Wang’s father told her about a project by the China Foundation for Poverty Alleviation (中国扶贫基金会) called “The Schoolbag of Love”. It is about donating schoolbags to kids in poor areas.

You can spend 100 yuan to buy a schoolbag full of school supplies (用品) at the post office. Then the workers there give you a list of kids in poor areas. You choose one of them to send your schoolbag to. After the kid gets the bag, he or she will mail a return postcard to you.

Wang thought it was a very good idea and she acted quickly. She chose to send the bag to Huang. Two weeks later, she got a postcard back from Huang.83. The two soon became good friends, sending messages and making phone calls to each other.

One thing affected (影响) Wang deeply after she made friends with Huang.

“It was 2:00 or 3:00 in the morning. I suddenly got her message telling me a small earthquake hit her place. Their house was shaking and they couldn’t sleep.”

Wang said she was moved because in panic (惊慌) Huang sent a message to her, meaning the girl saw her as a true friend.

84.Warmed by the friendship, Wang donated a second “schoolbag of love” to a girl in Xinyang, Henan last month. She also became a volunteer to introduce the schoolbag project to other communities (社区) in Beijing. “I like the project because I can get to know the people I help and make friends with them,” said Wang. “A  full schoolbag is also practical (实际的) help for students.”

根据短文内容简要回答问题。

小题1:Where is Huang Yuying from?

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小题2:How much does a schoolbag full of school supplies cost?

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(二)将短文中的划线句子译成汉语。

小题3:___________________________________________________

小题4:___________________________________________________

(三)请给短文拟一个适当的标题。

小题5:__________________________________________________

单项选择题