问题 单项选择题

某水泵配套的异步电动机安装在经常有人值班的机房内,需自起动运行,生产过程中没有过负荷的可能性。电动机额定电压为交流6000V、额定容量为460kW、额定电流 54.5A,起动电流为额定电流的5.6倍,在电网最小运行方式下电动机端:三相短路时,流过保护的最小三相短路电流为9160A,电流互感器变比为60/5,保护继电器采用接于两相电流差的DL-11/140型电流继电器,故障的相对灵敏系数为0.5。

验算电流速断保护装置灵敏系数为(),()要求。

A.8.8、符合

B.8.8、不符合

C.1.5、符合

D.1.5、不符合

答案

参考答案:A

名词解释
阅读理解

阅读理解。

     The world's biggest Internet search engine, Google, has proven once again to be king of the Web. Users

can download "Google Wi-Fi" software and then enjoy free Wi-Fi service available in some US cities since

last Tuesday.

     Wi-Fi is short for " Wireless Fidelity" (无线上网). It allows laptop computers (笔记本电脑) and personal

digital assistants (PDAs,个人数字助理) to connect to the Internet at high speed by radio signal.

     A person with a Wi-Fi enabled computer can connect to the Internet when near one of the network's

access points. The place covered by one or several access points is called a hotspot. Google has already set

up two"hotspots" in the US city of San Francisco which provide a free Wi-Fi service.

     The Wi-Fi technology even allows users to enjoy a free Internet phone service. Some scientists argue that

Wi-Fi may replace mobile phone networks.

     Wi Fi is still limited to a few cities, where there are"hotspots". But its capability (容量) of sending

information has already done better than that of the mobile phone network, even that of 3G(Third Generation

telecommunication technology). Some scientists have started to call Wi-Fi 4G.

     In addition to a high speed Internet connection, Wi-Fi has other advantages com pared to mobile phones.

Wi-Fi is global. The same Wi-Fi system works in different countries around the world. Different from using

cell phones, you don't need to change computers to use Internet phones when you go to other places and

most importantly, many Internet phones cost you nothing at all.

1. Wi-Fi is not available in cities without _____.

A. a computer

B. a radio

C. a hotspot

D. a cell phone

2. Which of the following is NOT the advantage of Wi-Fi?

A. The high speed Internet connection.

B. Many free Internet phones.

C. Using the same computers for Internet phones when you go to other places.

D. Used in all the US cities

3. Some scientists started to call Wi-Fi 4G, because _____. 

A. it is the product of the Google's 4th generation

B. it is more capable of sending information than the mobile phone network

C. it has been used by more than four generations

D. Wi-Fi will surely take the place of the mobile phone network

4. Which of the following is the best title?

A. Third Generation Telecommunication Technology

B. Free call Service

C. Google Launches Free Wi-Fi Service

D. Google, King of the Web