晶闸管触发电路中,若使控制电压UC=0,改变 ( )的大小,可使直流电动机负载电压Ud=0,使触发角α=90º。达到调定移相控制范围,实现整流、逆变的控制要求。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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