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/155108359515592487143252f4f2abb49256f0a446718image4.png" style="width:49px;height:25px;">

B、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1551083718055aaf1072c3a264eeab7f8b22936c98139.png" alt="上传图片">

C、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1551083595341d903c6faaa334d0eb2a2ab7789685ddbimage6.png" style="width:67px;height:25px;">

D、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1551083595405b97d45dd3e1d441197d1a84a29ac3124image7.png" style="width:49px;height:25px;">