Parameter Determination of a Multi-layered Induction Heating Coil: Analytical, Simulation and Experimental Studies

This paper presents methods for parameter determination of a multi-layered high-frequency induction heating coil (IHC). The prototype coil and power converter were designed and fabricated in the laboratory. To maintain the coil dimensions to be same as that of an existing CSI-fed coil in the laboratory, six layers are introduced to provide the requisite ampere-turns. The self- and mutual inductances of each layer and the associated stray capacitances need to be appropriately estimated and measured to successfully operate the voltage source inverter (VSI)-fed induction heating apparatus around resonance. This is essential due to the multiple zero crossings during commutation. The coil parameters are dynamic, which depends on the shape of the work-piece, material, frequency, temperature of the work-piece, etc., and have direct effect on the IHC performance as well as on the choice of power converter components. Skin and proximity effects are also studied closely and accounted for. Both analytical and FEM-based approaches have been adopted to determine the self- and mutual inductances at the appropriate frequency (nominally 11.5 kHz), both in the presence and absence of the work-piece (WP). The capacitance has been estimated using FE methods only. A general-purpose inverter stack (GPIS) made with SiC devices for some experiments was utilised for experiments. The self- and mutual inductance values have then been experimentally determined and are in good agreement with the estimated values, thus highlighting accuracy of analysis completeness of simulation model and precision of experiments. © The Institution of Engineers (India) 2024.