相关试题
【单选题】
What day is today?___
A. It's March 6.
B. It's a fine day today.
C. It's March.
D. It's Monday.
【单选题】
Is that seat taken?___
A. Please don't worry.
B. I don't think so.
C. Why not?
D. It's very nice.
【单选题】
Thank you for calling.___
A. Don’t mention it.
B. That's fine.
C. Nice talking to you.
D. Call back again.
【单选题】
How are you getting on today?___
A. Very well.
B. How do you do?
C. I'm a doctor.
D. Nice to have known you.
【单选题】
How's your family?___
A. Thanks all the same.
B. Thanks for calling.
C. Not too bad.
D. Don't mention it.
【单选题】
- How is it that you are late for class again?___
A. Because I missed the bus
B. By bus and then on foot
C. Yes, it is quite wrong
D. It is far from school
【单选题】
- Excuse me. Could you spare me a few minutes? - ___
A. Of course.
B. Of course not.
C. I am sorry to hear that.D.Yes. I'm busy now.
【单选题】
- It's very thoughtful of you to give me a ride. ___
A. It's my pleasure.
B. Take it easy.
C. Sure.
D. Never mind.
【单选题】
- This is heavy! What's in it? ___
A. I think you don't like it.
B. My new computer. I just bought it.
C. I'm glad you're here.
D. Are you really interested in it?
【单选题】
___ I'd like to place an order please.
A. Can I help you?
B. I can help you.
C. What are you doing?
D. Why are you doing?
【单选题】
- Do you know the girl over there?___
A. How can I know?
B. Yes, I remember it now.
C. It's Sam, my teacher's daughter.
D. She is a good girl.
【单选题】
- Shall we go out for dinner tonight?____
A. No, you can't.
B. Yes, please.
C. Thank you, I don't want to.
D. Sorry, I have a report to finish.
【单选题】
- I think the reference book（参考书）is very helpful.____
A. Good idea.
B. So do I.
C. With pleasure.
D. No problem.
【单选题】
- I wish you success in your career.____
A. You are welcome.
B. I think so.
C. Yes, please.
D. The same to you.
【单选题】
- Would you like to come over tonight?____
A. Yes, last night.
B. Yes, over there.
C. Sure, I'd love to.
D. Yeah, I liked it too.
【单选题】
- How do I transfer calls? ____
A. Do as you like.
B. It is a bit difficult.
C. Let me show you.
D. Not at all.
【单选题】
- Thanks for inviting me, John, but I've already made other plans. ____. Maybe another time.
A. I hope you enjoy it
B. That's good
C. Oh! I'm sorry to hear that
D. Great! I really had a good time
【单选题】
- Thanks for the lovely party and the delicious food. ____
A. No, thanks.
B. Never mind.
C. Thank you for coming.D.That's all right.
【单选题】
- Why didn't you tell me? ____
A. Sorry, I forgot.
B. I'm sorry you should wait.
C. I don't know.
D. I'd love to.
【单选题】
- What do you plan to do after the exam? ____ How about you?
A. I hate taking exams.
B. I like making plans.
C. Nothing special.
D. I've changed my mind.
【单选题】
- Tom told me that you collect stamps. ____
A. What do you mean?
B. I don't think so.
C. Why did he tell you?
D. Yes, I do. Do you?
【单选题】
- This is a challenging job. Who wants it？____
A. I'll take it.
B. It's a good idea.
C. You bet!
D. No sweat!
【单选题】
- I'm taking my driving test tomorrow. ___!
A. Cheers
B. Good luck
C. Come on
D. Congratulations
【单选题】
- ABC Company, may I help you? ____
A. I am Jack. May I speak to Miss Jenny?
B. This is Jack speaking. May I speak to Miss Jenny?
C. This is Jack speaking. Can I find Miss Jenny?
D. I am Jack. Can I find Miss Jenny?
【单选题】
- You have won the football game. Congratulations! ____
A. We are really lucky.
B. No one else could do it.
C. Oh, not really.
D. It's nice of you to say so.
【单选题】
- Excuse me, when will the 17:15 train arrive____
A. I don't tell you.
B. It's been delayed one hour.
C. You have to be patient.
D. Don't ask me.
【单选题】
- Is John there?____
A. Speaking.
B. I'm not Mary.
C. Who are you?
D. Mary is well today.
【单选题】
- Would you like to join us for Sunday dinner____
A. It's nice of you to invite me.
B. How about the food?
C. I like onion soup.
D. I'm sorry I missed the fun last time.
【单选题】
- Could you tell me where the nearest parking lot is?____
A. Don't ask me.
B. Parking is very difficult.
C. Sorry, I'm a stranger here.
D. Sorry, you can't park here.
【单选题】
- Sorry, ___
A. here you are.
B. take it.
C. it's taken.
D. never mind.
【单选题】
－What's this in English? ____
A. It's a map.
B. That is a map.
C. Yes, it's a map.
D. No, it isn't.
【单选题】
- I hear you got through your exam. Congratulations!____
A. No. I didn't do well enough.
B. Who told you that?
C. Thanks.
D. Yes, I got a good mark.
【单选题】
- Don't forget to come to my party this evening!___
A. I can't.
B. I won't.
C. I don't.
D. I will.
【单选题】
- Jim, please don't put your head out of the window on the bus. It's dangerous!___
A. Good idea.
B. Sorry, I won't do it again.
C. It doesn't matter.
D. It's good.
【单选题】
-How about going fishing?___, I have no patience for that.
A. Excuse me
B. Sorry
C. Pardon
D. Apologize
【单选题】
- Thanks for the lovely and delicious food______.
A. No thanks
B. Never mind
C. All right
D. My pleasure
【单选题】
－ Haven't seen you for ages. Let's have a get-together next week._____
A. Great idea.
B. Welcome!
C. Yes, of course.
D. No, thanks.
【单选题】
- Do you mind if I switch off the radio? ______. Go ahead.
A. Never mind
B. No way
C. No, not at all
D. No, you'd better not
【单选题】
- Could I use your bike for a moment? ___
A. It's well.
B. It doesn't matter.
C. By all means.
D. I have no idea.
【单选题】
-How do you like the story?_______.
A. I'd like to read it
B. I like it very much
C. fine, thank you
D. It's very interesting
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变频器输出的波形和载波频率有关，频率越高，越接近正弦波。
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脉宽调制调速电路不能改变送变电路输出电压的大小。
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变频器外接给定时，外接电位器的阻值可任意增大或减小。
【判断题】
在选择变频器容量时，最大负载电流可以超过变频器的额定电流。
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被控对象要求有较高的动态、静态指标且低速时有较硬的机械特性，应选用右李控制方式的变频器。
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电源侧电磁接触器可以频繁地控制变频器的启动和停止。
【判断题】
若电动机的转向不正确，可以把变频器的三根电源进线中的任意两根互换。
【判断题】
变频器在安装时，无严格要求，可以垂直安装，也可以水平安装。
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多台变频器接地时，应将一台变频器的接地端和另一台变频器的接地端相接后再接地。
【判断题】
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【判断题】
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【判断题】
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【判断题】
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【判断题】
对于高压变频器，为改善输出电压波形，减少转矩脉动，应采用增加直流侧电平的方法。
【判断题】
变频器在设定上限频率参数时，不应设定在 50Hz这个点上，根据实际需要可高于或低于 50Hz 。
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【判断题】
CPU22X 主机的输人点为 24V 直流双向光藕合输人电路，输出有继电器和直流 ( Mos 型）两种类型。
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高速计数器可以用于捕捉比 CPU 扫描频率更快的脉冲信号。
【判断题】
cPU22x 主机的输人点有继电器和直流（ MOS 型）两种类型。
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PLc 内部元素的触点和线圈的连接是由程序来实现的。
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主机箱体外部的 RS 一 485 通信接口，用以连接编程器（手持式或 PC ）。
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