Parasitic Capacitance Analysis of PCB-type Induction Heating Coil and LCCC/S Matching Network Design for Railway Turnouts

Conventional de-icing systems use resistive heating wires to prevent the freezing of railway turnouts. Because of the low efficiency of the heating wires, induction heating (IH) systems have been investigated recently. The IH systems utilize high-frequency resonant inverters and heating coils to induce eddy currents and heat energy on heating plates. The heating coils can be manufactured with a printed-circuit-board (PCB) process. However, a short distance between PCB patterns can generate a significant parasitic capacitance, which resonates with the coil inductance. A self-resonance of the coil makes capacitive impedance at high-frequency ranges and distorts coil currents. This paper investigates the parasitic capacitance of PCB-type induction heating coils. Analytic models of the PCB-type heating coil are derived. In addition, a new LCCC/S impedance matching network (IMN) design that compensates for the parasitic capacitance is presented. The developed induction heating coil and IMN are demonstrated using experimental results.