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【单选题】
关于AutoCAD的空间,哪种说法是正确的?( ) prefix="o" ns="urn:schemas-microsoft-com:office:office" ?xml:namespace>A.
AutoCAD有模型空间和图纸空间两种
B.
图纸空间也是三维图形环境
C.
在图纸空间中不可建立二维实体，它仅用于绘图输出
D.
图纸空间建立的二维实体也可在模型空间显示
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【简答题】Alternator
【简答题】alternator
【单选题】An alternator switchboard has a synchroscope and synchronizing lamps, if the synchroscope is broken, which of the steps listed is the most essential before an alternator can be paralleled with the bus...
A.
The breaker should be closed when one synchronizing lamp is dark and the other is bright
B.
The breaker should be closed when both synchronizing lamps are bright
C.
The frequency meter should be used to determine that the incoming alternator frequency is slightly higher than the bus
D.
A portable phase sequence indicator must be used to verify the information from the lamps
【单选题】What is the purpose of the alternator reverse power trip?
A.
To prevent the alternator from “motoring” by being supplied power from other parallel alternator
B.
To prevent parallel operation if the excitation field voltage is reversed
C.
To prevent the alternator from being paralleled if it is out of phase with the main switchboard
D.
To give automatic disconnection of the circuit breaker when you are taking the alternator off the switchboard
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