单项选择题
A.field excitation of both units is adjusted B.governors of both units are adjusted C.phase sequence is altered D.kilowatt load is evenly divided
An advantage of DC motors over AC motors is that they （...
单项选择题An advantage of DC motors over AC motors is that they （）
A.are less expensive B.require less maintenance C.can be started across the line D.offer a more effective means of controlling speed
Which of the following devices are protected from being...
单项选择题Which of the following devices are protected from being motorized by a reverse-power relay?（）
A.Alternators B.Wave guides C.Exciters D.Amplidynes
If the length of a wire is halved and the cross-section...
单项选择题If the length of a wire is halved and the cross-sectional area is doubled, the resistance will be （）
A.quartered B.unchanged C.doubled D.quadrupled
