动车组高压牵引系统工作原理：受电弓将接触网电压引入牵引变压器降压后送入牵引变流器，牵引变流器将交流电整流为直流电，滤波后逆变为电压和频率可调的三相交流电，供给牵引电机实现牵引运行。
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动车组高压系统的避雷器的功能：避免雷电或过电压损害牵引变压器、牵引变流器等设备。
A. 对
B. 错
以下哪一种菌通称为痢疾杆菌?()
A. 肉毒梭状芽孢杆菌
B. 椰毒假单胞菌酵米面亚种
C. 副溶血性弧菌
D. 志贺氏菌
Beihai Park is a beautiful park____built about 300 years ago
A. where was
B. that were
C. which was
D. where
He is poor, but the way how he behaves looks he _____ rich.
A. is
B. were
C. was
D. had been
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