Solid-State Contactor with Si Thyristor and SiC FET Hybrid Module for High-Efficiency Motor Control

Solid-state contactors are an emerging solution in various load-switching applications such as direct-on-line starting of induction motors. The design challenge of solid-state motor contactors (SSMCs) comes from a high motor-starting inrush current defined in IEC 60947-4-2 standard. To overcome the limitation of conventional SSMC solutions using silicon thyristors (Si SCRs), a novel “ThyFET” topology is proposed to combine the high inrush tolerance of Si SCRs with the efficient nominal conduction of silicon carbide junction field-effect transistors (SiC JFETs). In this paper, the ThyFET circuit is first analyzed with current commutation principles and switching waveform simulations. Next, the packaging design of a 1.2 kV, 12 A, three-phase, bidirectional ThyFET module is presented, which adopts a three-dimensional structure to minimize the module footprint meanwhile handling the thermal stress. The ThyFET SSMC prototype is then assembled and evaluated with IEC-standardized benchtop tests and direct-on-line motorstarting tests with a 480 V, 5.6 kW induction motor load. The test results have validated the light-load efficiency boost and the distortion reduction in the ThyFET SSMC as compared to commercial SSMC products. Finally, the outstanding inrush handling capability of the ThyFET circuit is highlighted by comparing to other hybrid Si/SiC switches in the literature.