问题 问答题 简答题

在转速、电流负反馈双闭环直流调速系统中,电流调节器有哪些作用?

答案

参考答案:

①作为内环的调节器在转速外环的调节过程中,使电流紧紧跟随其给定电压(即外环调节器的输出量)变化。

②对电网电压的波动起及时抗扰的作用。

③在转速动态过程中,保证获得电机允许的最大电流。

④当电动机过载甚至堵转时,限制电枢电流的最大值,起快速的自动保护作用。一旦故障消失,系统立即自动恢复正常。

阅读理解

One day in Overtown, Florida, 3.7 million dollars fell from the sky! It happened when a truck turned over. There was money everywhere! One man said, “The streets were like gold.” Some people took off their shirts and filled them with money.

Police officers went from door to door in the neighborhood. They asked people to return the money. After six hours, the total returned: zero.

No one in Overtown was surprised. Many people in this town are poor. They need the money to buy food for their children. They think that God sent the money to them.

The police say this is a serious crime. “People took thousands of dollars. It’s not their money, and they have to return it.” The police also say it’s dangerous to keep the money because everyone knows the story from the news. People have money in their pockets and their backyards, and other people will try to steal it.

So far, only one person has returned some money. He is a firefighter. He found 300,000 dollars in a bag and gave it to the police. The people of Overtown still have the rest of the money.

小题1:People filled their shirts with the money from  _______.

A.the sky

B.a truck

C.a bank

D.a shop小题2:What does the underlined word “crime” in the fourth paragraph mean in Chinese?

A.金钱

B.犯罪

C.损失

D.德行小题3:Where did people hide the money they got?

A.In their kitchens.

B.In their bedrooms.

C.In their backyards.

D.In their sitting rooms.小题4:How much money was still missing?

A.3.7 million dollars.

B.300,000 dollars.

C.3.4 million dollars.

D.700,000 dollars.小题5:Which is the best title for the passage?

A.Money from the Sky.

B.Police and Money.

C.A Truck of Money.

D.Poor People and Money.

单项选择题