问题 问答题 论述题

异步电动机在进行大修或绕组重绕后电流增大可能有哪些原因?

答案

参考答案:

常见原因有:

(1)大修后对电动机转子进行车削处理,必将造定子与转子间的气隙增大,使磁阻增加,电流增大。

(2)大修后装配质量不符合要求,如机械配合不好、轴承润滑不当、发生错装或漏装等。在拆除定子绕组时绕坏了定子铁心,使硅钢片退火或片间绝缘损坏,导致涡流增大,导磁。

(3)率下降,使电流增大。

(4)新绕组数少于原匝数。

(5)绕组接线错误,如将星形接成三角形,绕组串联接成了并联等等。

阅读理解

阅读理解。

     Hands play an important part in our daily life. But do you know which of your two hands you use more?

Very few people use both hands equally well. Most of us are right-handed. Only about five people out of a

hundred are left-handed. New-born babies can take hold of things with either of their hands, but in about two

years they usually use their right hands. Scientists don't know why this happens.

     Monkeys are our close relatives in the animal world. Scientists have found that monkeys like to use one of

their hands more than the other, but it can be either hand. There are as many right-handed monkeys as

left-handed ones. Next time you visit a zoo, watch the monkeys carefully, you will see that some of them will

use their right hands and others will use their left hands. But most of the people use their right hands better and

this makes life difficult for those left-handed people. We live in a right-handed world.

1. How many people among 100 people use their left hands better?

A. 5%.

B. 50%.

C. 95%.

2. What's the meaning of the underlined word "equally" in Chinese?

A. 公正地

B. 均等地

C. 平凡地

3. New-born babies can use __________.

A. both of their hands

B. neither of their hands

C. their right hands

4. Which of the following is true?

A. There are more monkeys using their right hands than left hands.

B. There are more monkeys using their left hands than right hands.

C. There are as many right-handed monkeys as left-handed ones.

5. "We live in a right-handed world." means __________.

A. Most people use their right hands better.

B. Few people use their right hands better.

C. Half of the people use their right hands better.

单项选择题