The Soft Starting System for an Induction Motor with an Induction Resistance in the Wound Rotor Circuit

In the electric drive, made on the basis of an induction motor with a wound rotor (IM with WR), it is proposed to regulate the rotor current by means of a rectifier-inverter unit, while the rectifier input is connected to the rotor winding pins of the motor, and the output of the inverter based on IGBT transistors with reverse diodes - to frequency-dependent inductive-active resistance, a capacitive filter is included in the DC link. The electric drive system implements a soft start-up of an induction motor with a wound rotor with the ability to control and maintain a constant starting torque with the required acceleration. Such an electric drive system has been proposed to be used on metallurgical production conveyors, which often do not require speed control, but provide start-up modes with a given acceleration rate, including when the conveyor is fully loaded. The drive system combines some of the properties of the asynchronous valve cascade (AVC) and parametric control systems. The operation of the inverter control system is described, which realizes the stabilization of the rotor current of the induction motor by changing the frequency at the output of the inverter voltage as a function of the rectified current of the motor rotor. The frequency-dependent inductive-active resistance, called induction resistance, contains a massive magnetic core with three tubular rods connected by a yoke, on each of the rods is placed a single-layer phase winding. The wall thickness of the tubular rods does not exceed the depth of penetration of the electromagnetic field into the massive ferromagnetic material. The results of experimental studies of the frequency characteristics of induction resistance are presented. A mathematical model of the electric drive system has been developed, computer simulation of dynamic processes has been carried out using the MATLAB Simulink software package. The possibility of implementing the proposed method of controlling the process of starting an induction motor with the stabilization of the starting torque has been proven.