Abstract
Recently, large rolling mills have been used in steel industry, so that cycloconverter-fed AC motor drives have been applied to the systems. For the systems, there are induction motor drives with advantage of easiness of maintenance, and synchronous motor drives with advantage in view of power factor and converter capacity. Both kinds of motor drives are controlled by vector control method, because the rolling mill drives need high performance variable speed control. The control method and its characteristics for the vector-controlled AC motor drives have been discussed. However, the characteristics of the method for synchronous motor drives have not sufficiently been described.
In this paper, decoupling control method for the vector-controlled synchronous motor with field and damper windings is proposed. The necessary transfer functions for the designing the vector control system are derived and it is shown that the method of high performance variable speed and power factor control are obtained. Then, the characteristics of the method are confirmed by the simulation results. In the decoupled system, the transfer functions between the voltages (armature and field) and currents are the first order lag and the transfer functions between the currents and armature flux are the first order lead-lag. Consequently, stability and response performance of the decoupled synchronous motor drives can be designed with suitable characteristics by this control strategy.
