[判断题]挂车试拉，连结员确认车列全部起动，向调车长回示好了信号。
A.正确
B.错误

答案： 

解：当cosj =0.8（滞后）时，sinj =0.6，电压调整率

DU_N= (r^*_k75℃cosj +x^*_k75℃sinj)×100%

= (0.008×0.8+0.0725×0.6)×100%

= 4.99%

当cosj =0.8（超前）时，sinj = -0.6，此时的电压调整率

DU_N= (r^*_k75℃cosj -x^*_k75℃sinj)×100%

= (0.008×0.8-0.0725×0.6)×100%

= -3.71%

答案：在额定负载下，cosj =0.8（滞后）和cosj =0.8（超前）时的电压调整率分别为4.99%、-3.71%。