Low tension cascade mill speed control by current measurement with temperature compensation

摘要

A cascade speed control for tensionless production in a rolling mill by the measurement of stand motor current with temperature compensation. A low tension speed ratio between pairs of mill stands is calculated by successive incremental corrections. The corrections are based on the difference between a no tension current and a tension current for the motors of the mill stands as compensated for temperature variation. In one embodiment a compensation factor is calculated by taking the temperature difference of the material at the times the currents are measured and multiplying the difference by an empirical constant which relates the change in motor current to a change in temperature for a particular plant. Another embodiment illustrates temperature compensation by using current compensation values which are obtained by storing a no tension current profile for one of the mill stands. The low tension speed ratios between stands are maintained by cascading variations in the speed of a subsequent stand down to a previous stand.