Argon ICP plasma torch at atmospheric pressure driven by a SiC based resonant converter operating in MHz range

In this work, the challenge of driving an Argon inductively coupled plasma (ICP) torch at atmospheric pressure, with a high-frequency resonant converter is approached. Based on wide bandgap semiconductor power devices, these converters reach efficiencies over 90% in MHz range for powers up to tens of kW. This makes the efficient power conversion in applications like plasma torches possible, which are typically driven by valve amplifiers with relatively low efficiencies. However, due to the strong impedance variations of ICP loads with power and frequency, special considerations must be taken for the design of such a system. FEM simulations of the torch were performed showing the expected impedance variations in range of 1 to 14MHz and 1 to 15kW. An experimental Argon torch prototype was built and driven by a Silicon Carbide (SiC) resonant converter operating at 3MHz. Impedance measurements were performed at different operating points and compared with simulation results. A global analysis of the whole system is included, showing the important considerations for understanding and designing such a system.