Medium plate plant of chongqing iron & steel has reconstructed technically the original two stand rolling mills ( roughing mill and finishing mill ) and changed dc drive system into ac frequency converter drive system 重庆钢铁集团公司中板厂对两台主轧机(粗轧机和精轧机)驱动系统进行了技术改造,将原来的直流驱动系统全部改造成变频调速驱动系统。