A Mathematical Model of the Power Circuit of Main Electric Drives of Rolling Mills

Abstract

A mathematical model of the power circuit of the main electric drive of cold rolling mill 2.0 m is described. Mathematical model includes a transformer and an active rectifier.  A distinctive feature of the power circuit the main drive is to use a transformer with a serial connection of primary windings. To implement the twelve pulse circuit the secondary windings of transformers have different groups of connections. The algorithm for generating the input voltage of the active rectifier is made on the model by comparing the switching angles with the reference signal increases linearly over the period of the supply voltage. Switching angles are calculated based on the method of pulse-width modulation with the selective harmonic elimination. Active rectifier model allows obtaining the phase voltages at the input capacitors relative zero point and calculating the primary currents of transformers, which is due to the difference in the flow network and EMF voltage at the input of the active rectifier. The simulation results are used to assess the electromagnetic compatibility powerful active rectifiers with supply mains and select transistors switching angles to minimize THD voltage.