Hybrid Solid State Switch for the Efficiency Improvement in Controlling AC Motors

This paper introduces a new circuit topology of power semiconductor switching devices for a high efficiency and cost-effective solid-state switch, especially for motor control applications. The proposed topology involves the combination of Thyristors (SCR) and Field Effect Transistors (FET) in a parallel arrangement. This new configuration permits the maximization of efficiency and enables higher power density through the minimization of the heat load compared to state-of the-art solutions. Whereas power loss during nominal current operation are minimized by the conduction characteristic of Field Effect Transistors, power loss during high current conditions (e.g. occurring during magnetizing inrush currents and motor start overcurrent) are minimized by the conduction characteristic of Thyristors. In this paper, we describe this novel circuit topology and the control circuit, and we validate the performance of the topology through full power experimental validation for a 480 V, 7.5 Hp induction motor in both continuous 12A operation and 8-time rated current of overcurrent capability tests.