【判断题】一级负荷必须由两个独立的电源供电,二级负荷应尽量由双回路供电。
【简答题】Amy is an American student in Des Moines, Iowa. She is nine years old and she is in Grade Four this year. Now she and her friends are pen pals of the students in India. In their letters, Amy learns th...
【单选题】Which city had the lowest temperature?
【单选题】A confusing man whom you don’t know is standing, with a map in his hand , A B C on a street corner . No er...
【单选题】一个电阻,接在10V的直流电源上,产生的功率为P。把它改接在正弦交流电源上,使其产生的功率为P/2,则正弦交流电源电压的最大值为( )
【单选题】对一级负荷中的特别重要负荷( )。
B.
除由两个电源供电外,尚应增设应急电源,并严禁将其他负荷接入应急供电系统
C.
应由两个电源供电,当一个电源发生故障时,另一个电源应不致同时受到损坏
D.
可采用一路电源供电,但必须采用应急发电机组作为第二电源