Planar Tesla coil arc ignition transformer for a plasma cutting power supply

摘要

The arc igniter in a plasma cutting system is a High Voltage High Frequency (HVHF) Pulse Generator typically realized using a Tesla coil resonant circuit. The ignition voltage pulse is a 5–15kV pk., 2–3 MHz sinusoid lasting for not more than 5–10 cycles. It is used to ionize the gas inside the torch thereby producing plasma [1]. The Tesla coil resonant circuit is the preferred method since it is composed of rugged components like the Tesla coil transformer, spark gaps and capacitors. However, the conventional Tesla coil transformer is expensive since it requires a special custom bobbin and the windings are manually wound. This also leads to variations in unit to unit performance. In view of this, a planar technology based Tesla coil transformer as a cost effective alternative is proposed. With this approach, there is no need for a custom bobbin or manual winding. This simplifies the build, reduces cost and ensures consistency in unit performance. The design procedure consists of obtaining characteristics of the current transformer and designing the planar version to match those characteristics. Details of the design procedure are covered in the paper. FEA (Finite Element Analysis) based models of the current and planar Tesla coil versions are used for the electromagnetic analysis and validated with experimental data. Reasonable correlation is obtained with experimental data over a 1 kHz–3 MHz frequency range. This confirms the efficacy of the analysis and the feasibility of planar technology for this application.