电牵引采煤机如何改变电机转速?
参考答案:电牵引采煤机要改变电机转速,可以通过保持激磁电流不变,采用晶闸管触发电路来改变可以得到恒转矩调整段方法达到。
--- Can you tell me ______ it is from here to the Summer Palace?
---Let me see. It's about 15 minutes' ride.
A.how far
B.how soon
C.how much
D.how long
钱乙学医的老师是()
A.钱颢
B.吕君
C.长桑君
D.许文懿
E.罗知悌