某车间有一台不频繁起动的笼型异步电动机,电气参数为:额定功率160kW,额定电压为交

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问题:

某车间有一台不频繁起动的笼型异步电动机,电气参数为:额定功率160kW,额定电压为交流三相380V,额定功率因数0.85,额定效率0.93,额定起动电流倍数7倍。该电动机由一台额定容量500kVA,电压10/0.4kV,阻抗电压4%的变压器供电。变压器到电动机由电缆连接,线路阻抗为0.01Ω。变压器一次侧短路容量为25MVA。变压器二次母线上其他负荷的无功功率为178kvar。电动机起动前变压器二次母线电压为额定电压380V,试计算电动机起动时有关参数并判断电动机是否可以采用全压起动。

变压器母线上的短路容量为()。(选最接近的一个数据)

A.8.333MVA

B.0.678MVA

C.4.167MVA

D.83.33MVA

考点:电气工程师(供配电)电气传动电气传动题库
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洁净度低于5的系统,空调器漏风率不应大于()%。

A、1

B、2

C、3

D、4

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Through watching the National Day parade roll down Tian’anmen Square last Thursday, foreign observers were impressed by China’s fast development and growing strength

China’s military parade, the birthday celebration was a showcase of fighter jets, tanks and ballistic missiles(弹道导弹).The display included 100,000 marchers, 80,000 children, 8,000 soldiers and 151 planes.President Hu Jintao, whose Mao suit(中山装)interested foreign media, told the watching nation that the Chinese people were “full of confidence,” USA Today reported.“Today, a socialist China, facing modernization, the world and the future, has stood rock-firm in the east of the world,” he said.

The celebration marked the day in 1949 when Chairman Mao Zedong announced the founding of the People’s Republic of China.In the years since, the nation has grown into the world’s third largest economy.

The Associated Press(美联社)quoted Geremie Barme, a China expert at Australian National University as saying that the displays “meant” to educate, excite, unite and entertain”.The New York Times said that while China’s military is still behind those of many developed nations, its progress since the last parade in 1999 was clear.

The rapidly improving ability of China’s army has worried some overseas analysts.Reuters said that Dongfeng 21C, the anti-ship missile, could force US aircraft carriers(航空母舰)to stay farther away from China’s waters, if models were developed into more powerful ballistic missiles.

Russell Moses, a political analyst, said China’s leaders are “right to congratulate themselves, but real test is not how they deal with success but how they deal with present challenges.” Among these are the imbalance in development between the town and the country, unemployment and the environment.

53.In total, ____people took part in the National Day military parade last Thursday.

A.100,000      B.88,000         C.188,000       D.188,151

54._______reported the overseas analysts worry about the rapidly improving ability of China’s army.

A.Reuters      B.The Associated Press  C.USA Today   .D.The New York Times

55  Which of the following is TRUE?

A.Foreign media paid little attention to President Hu’s Mao suit

B.Foreign media were only impressed by China’s rapid development

C.Dongfeng 21C has driven US aircraft carriers away from China’s waters

D Ten years ago, another National Day military parade was held in Beijing

56  What can be inferred from the passage?

A.China has successfully completed the processed of modernization

B.The US aircraft carriers are now staying not far from China’s waters

C.China’s military has caught up with most of the developed countries

D.There is a gap in development between China’s urban and rural areas

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你认为自己的地理教学有哪些特色

题型:单项选择题 案例分析题

()年()月()日,香港终于回到祖国的怀抱。

A.1997.7.1 

B.1999.7.1 

C.1997.12.20 

D.1999.12.20

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