Application of Transfer Switch in Mining Converters

Excavator systems like electric shovels are critical high power equipment in the mining industry. The individual motions of a shovel system are called hoist, swing, crowd and propel. All the motions are powered by AC asynchronous motors which are fed by IGBT vector controlled inverters. The propel system consists of two independently controlled motors. A transfer switch allows sharing of inverters between hoist and propel 1 or crowd and propel 2 motor operations. The transfer switch is controlled by the PLC. Typical industrial transfer switches consist of a motor module which drives multiple switch modules. The switch modules could be single pole double throw or double pole, double throw. The motor module being a mechanical device needs greater than 2 seconds to perform a transfer. This paper proposes to a solution to integrate two single pole disconnect switches to operate them as a single pole double throw changeover switch. The objective is to gain improvements in the transfer time. The proposed scheme is supported by experimental results.