一台三相感应电动机拖动额定恒转矩负载运行,若电源电压下降 ,此时电机的电磁转矩( )。

A、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/15453738034067308ad996e6441cf993215958ad584c4image2.png">

B、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/154537380350505f2aaf37b3a4d50a7c435556d76d61eimage3.png">

C、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1545373803598eb88aec4cdef490e94ccd2fb8a9b40daimage4.png">

D、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1545373803698476ce73ca0404e3b85b23ccbf5151468image5.png">