In high-speed wire rod mill, the finishing mill adopts collective transmission mode, which is due to:
1) In order to shorten the excess length of the head and tail of the rolling piece caused by drawing, the structure of the rolling mill is required to be as compact as possible, so that the space between the stands is very small. Under this compact condition, it is impossible to arrange the rolling mill as a single transmission.
2) The finishing mill of high-speed wire rod mill not only has high speed but also needs to be adjusted to different speeds according to different product specifications. If it is driven separately, the number of frames is large, and the speed required by different product specifications varies greatly in different sorties. Therefore, the required electrical control system will be very complex, and at the same time, it must have high sensitivity to adapt.
Therefore, even if the electrical system can do it, it is difficult to maintain the micro-tension rolling relationship between the racks for all product specifications.
3) The combined structure of collective transmission greatly improves the dynamic speed drop of the motor at the moment of biting and makes the micro-tension relationship between the stands unaffected by the electrical equipment, thus creating favorable conditions for the micro-tension rolling at high speed.
In summary, the design of roughing mill, medium rolling mill and pre-finishing mills using AC motor drive alone, finishing mills using AC motor collective drive.