# Induction Coil Design Considerations for High-Frequency Domestic Cooktops
## 1 Introduction  
Domestic induction cookers, whose basic operating principle is based on Faraday's law, have been a subject of interest for a long time due to the rapid heating, high efficiency, functionality, hygiene, and safety they provide, as well as low carbon emissions, which are of great importance today. The high-frequency magnetic field produced by means of a power converter and induction coil induces eddy currents on the bottom of the pot and manifests itself as heat with the help of the skin effect [1, 2]. Conventional domestic induction cookers use Si-based IGBTs as a power semiconductor due to their low saturation voltages and moderate switching performance. Si-MOSFET, which could be used at (600-650) V voltage level, shows quite a high equivalent resistance (\(\mathrm{R_{DS_{nn}}}\)). The resonance frequency of these designs ranges from 18 kHz to 50 kHz because of the limited switching characteristics of Si-based IGBTs at the turn-off. Low-switchingfrequency causes bulkier passive components such as resonance capacitors and induction coils [3; 4; 5; 6; 7; 8; 9]. WBG power semiconductors are gaining more and more ground in modern domestic induction heating applications. These new-generation power semiconductors have superior switching performance and reasonable on-state resistance compared to their Si-based counterparts [10; 11; 12]. Electric field strength is directly related to the thickness of the semiconductor layers used. The higher the electric field strength of the material, the thinner the layer will be used. Thus, the equivalent resistance (RDSon) formed in the drift region decreases and the conduction loss decreases. In addition, the thinning of the layers used will have a positive effect on the switching speed; therefore, the switching losses will also decrease. The average speed gained by the electrons in the electric field is defined as drift speed. This parameter is directly related to the switching speed. The higher this value is, the higher the speed at which the power semiconductor can switch. Thermal conductivity is a very critical feature for power converters. To design the cooling system and increase the power density of the circuit, the semiconductor is expected to have very good thermal conductivity. Better thermal conductivity leads to the design of more compact package cases at the same power level. For this reason, there are many studies on their use in domestic induction heating applications [13; 14; 15; 16; 17; 18; 19]. However, these switches, which provide a very high switching frequency capacity, require different induction coil designs than traditional domestic induction cookers. The induction coil is a very critical component as it directly affects the maximum value of the power to be transferred, efficiency, and cost. There are some important points to consider in coil design [20; 21; 22; 23]. The first point to consider is the skin effect, which is the uneven distribution of the current density of a conductor through which an alternating current flows (see Section 3.1). Therefore, the resistance seen under DC current (RDC) and the resistance seen under AC current (RAC) is different. The resistance seen under AC current is higher. The second point is the proximity effect, which is the disruption of current distributions as a result of the magnetic fields created by two conductors carrying current in the same or opposite directions affecting each other (see Section 3.2). Since the high-frequency alternating current produced in induction heating systems is passed through the induction coil to produce a magnetic field, additional precautions must be taken to minimize copper losses (I\({}^{2}\)R) that will occur on the induction coil. The most basic precaution to be taken for the induction coil is to produce the coil with litz wire. Thanks to the litz wire, the surface area where the current flows is increased, thus reducing the winding resistance that will occur.