问题 问答题

试述小惯量型直流伺服电动机和普通型直流伺服电动机的工作特点。

答案

参考答案:

解析:(1)小惯量型直流伺服电动机的特点为:转子惯量小,适合于快速响应的伺服系统,但其过载能力低。 (2)普通型直流伺服电动机的特点为:①低速时输出的转矩大,惯量比较大;②转子的热容量大,电动机的过载性能好;③调速范围宽,可达1:1000以上;④通过加大电源容量可以作到加速度大,响应快;⑤转子温升高。

阅读理解

Dinner customs are different around the world. If you are a guest in Ghana( 加纳), this information will help you a lot.

In Ghana, dinner is usually from four in the afternoon to six in the evening. But there are no strict rules about time. Whenever a guest arrives, a family offers food. When you go to a home, the person who receives guests takes you to the living room first. At this time everyone welcomes you. Then you go to the dinning room. There you wash your hands in a bowl of water. All the food is on the table.

In Ghana you usually eat with your fingers. You eat from the same dish as everyone else .But you eat from one side of the dish only. It is not polite to get food from the other side of the dish. After dinner, you wash your hands again in a bowl of water.

Most meals in Ghana have a dish called fufu. People in Ghana make fufu from the powder(粉末) of some plants. Sometimes they cut the fufu with a saw(锯子) because it is very hard. You must chew(咀嚼) fufu well, or you may get sick. You eat fufu with the fingers of your right hand only.

小题1:From the passage we know that in Ghana ______________.

A.the rules for dinner time are not strict

B.dinner is always at six in the evening

C.a family offers food only at four in the afternoon

D.people usually invite their guests to dinner late in the evening小题2:People in Ghana usually eat ________.

A.from one side of a dish to the other

B.from the other side of the dish

C.with their fingers

D.with their spoons小题3:In fact, most dishes in Ghana _______.

A.are cooked with the powder of some plants

B.have fufu in them

C.are too hard to eat

D.are not very hard小题4:When you eat fufu, you’d better _________.

A.cut it with a saw

B.use your right hand only

C.chew it well

D.all of the above

单项选择题 A1型题