Analysis of DC Motors Commutation of Broadband Hot Rolling Mill

One of the factors affecting the reliability of DC motors (DCM) is the quality of brush collectors’ commutation. The problem of commutation conditions improvement is relevant for the thyristor electric drives of rolling mills most of them being in operation for a long time. A set of experimental studies was conducted for the motors of the broadband hot rolling mill 2000 stands. The authors define the mechanical and electromagnetic factors impacting the collector sparking. For this purpose, a set of experiments was conducted to measure electromagnetic induction in the gaps under the main and additional poles as well as to assess the quality of the collector surface. The measurements were made using commercially available control and measuring devices and specially manufactured sensors. As a result of the waveform processing, the causes of the deterioration of the commutation conditions were revealed. The main ones are the deviations allowed at the installation of the main and additional poles from their symmetrical position, the low inductance of the smoothing chokes, the reverse tachogenerator pulsations. The measures recommended for eliminating these bottlenecks are replacing existing tachogenerators with pulse speed sensors and increasing the inductance of smoothing reactors.