问题
单项选择题
异步电动机VVVF调速系统的机械特性最好的是（）
A.恒压频比控制
B.恒定子全磁通控制
C.恒气隙磁通控制
D.恒转子全磁通控制
答案
参考答案：D
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异步电动机VVVF调速系统的机械特性最好的是（）
A.恒压频比控制
B.恒定子全磁通控制
C.恒气隙磁通控制
D.恒转子全磁通控制
参考答案：D
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| Nowadays more and more Chinese teenagers find life more difficult without their parents. They don't know how to do 1 . Because their parents do almost everything for them at home. This is a big problem. Joy is 14 years old. One day her parents went away 2 business, so she had to stay at home alone. At first she thought she would be happy 3 her parents were not in. She could do everything 4 she liked. But it was six o'clock in the afternoon, she felt 5 . "Oh, it's time to have supper. Where can I get my food?" she said to herself. Later she found some food in the fridge, but she 6 know how to cook. At that moment, she missed her 7 very much. At last she could only go to the supermarket and 8 some food to eat. Many of teenagers are 9 as Joy. So I think they should learn some basic life skills, like cooking, tidying up their rooms or dressing themselves 10 . They shouldn't depend too much on their parents. | ||||
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