问题 问答题 简答题

对交流不停电电源系统的基本要求是怎样的?

答案

参考答案:

⑴保证在发电厂正常运行和事故状态下,为不允许间断供电的交流负荷提供不间断电源。在全厂停电情况下,这种电源系统满负荷连续供电时间不得少于0.5h。

⑵输出的交流电源质量要求为:电压稳定度在5%~10%范围内,频率稳定度稳态时不超过±1%,暂态时不超过±2%,总的波形失真度相对于标准正弦波不大于5%。

⑶交流不停电电源系统切换过程中,供电中断时间<5ms。这样的切换时间只有静态开关才能做到。

⑷交流不停电电源系统必须有各种保护措施,保证安全可靠运行。

阅读理解

根据短文内容,回答问题。

     Dick is seven years old. He begins to go to school this term. He studies very hard and listens to the teachers

carefully. He is polite (礼貌) and has lots of friends. So they all like him very much.

     It's Saturday today. Dick, his sister Kate and his mother stay at home. His mother is doing some housework

and he is watching TV and the girl is doing her homework. At ten his father comes back from the farm with a

bag of apples. The boy likes them very much and wants to eat some. His mother gives him four apples and says,

"Go to wash them in the kitchen."

     Dick washes the apples and then gives them back to his mother. The woman says, "Which apple do you

want, Dick?"

     "The biggest one, Mummy."

     "What?" says Dick's mother,"You should be polite and want the little one."

     "Should I tell a lie just to be polite, Mummy?"

1. At what age do children begin their schooling in Dick's country?

    _____________________________________________________________

2. Is Dick's sister a student? 

    _____________________________________________________________

3. Why does the mother ask Dick to wash four apples

    _____________________________________________________________

4. Who do you think may eat the biggest apple?

    _____________________________________________________________

5. What's the meaning of "just to be polite" in the last paragraph in Chinese?

    _____________________________________________________________

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