# Induction Coil Design Considerations for High-Frequency Domestic Cooktops
## 1 Introduction
The proximity effect increases as the distance between the conductors decreases and the operating frequency increases. To prevent this, some precautions can be taken in the coil design. The first of these is to increase the distance between the windings by placing the windings in a plastic carcass. This method reduces the proximity effect while increasing the coil cost. Another precaution is to reduce the coil wire diameter and increase the number of wires. This approach requires the creation of more complex litz wire structures, which in turn necessitates an appropriate production capability to produce these types of coils [24; 25; 26]. Magnetic cores are used in induction coils to obtain the target inductance and coupling. These magnetic cores are exposed to higher speeds of magnetic field changes with increasing switching frequencies. Core losses in magnetic materials are proportional to the magnetic field change and frequency. While the magnetic cores used in conventional induction coils are used between approximately 20 kHz and 50 kHz, the switching frequency is expected to be above 100 kHz in designs made with new-generation switches. For this reason, the high-frequency characteristics of the cores to be used must be of much better quality. However, this situation creates a disadvantage in terms of cost. The third point to consider is the appropriate power transfer. To transfer the required power at the desired switching frequency in the system, the parameters of the resonance tank must be tuned very well. For this reason, the equivalent resistance and inductance values created by the induction coil and pot equivalent circuit must be adjusted precisely. Otherwise, transferring power with high losses at high switching frequencies will reduce product performance and cause thermal design difficulties. In addition to design difficulties, high switching speeds also offer several advantages over conventional designs. As the frequency increases, the skin effect on the metal increases. As the skin effect increases, the surface resistance increases, thus making it possible to heat metals that do not respond to magnetic fields without the need for complex and expensive induction coil structures. While some studies suggest costly and complex coil structures to heat these types of pots, others increase the switching frequency by changing the power circuit. However, with the arrival of the WBG switch, direct heating is possible without the need for conventional methods [27; 28]. Another advantage of the increased surface resistance is that it allows the installation of systems with lower magnetic coupling. Thus, a design can be made using a lower number of windings and a magnetic core. This provides great benefits in terms of cost and efficiency. In this study, coil design in domestic induction cookers with high switching frequencies is discussed. The positive and negative effects of operating at high-frequency levels on the induction coil are assessed. Designs and analyses for both high-power and low-power systems are included. The point to be considered in coil design is core losses. Since core loss increases at high frequencies and the induction ambient temperature is very high, magnetic saturation may occur. Therefore, magnetic cores suitable for high frequencies should be preferred. Since the skin effect that will occur in the coil windings will increase because of the high frequency, copper losses that will occur in the coil will increase. This situation has a negative effect on efficiency and power transfer. Therefore, each conductor of the litz wire should be selected with a lower cross-section. The number of conductors will be increased when the conductor diameter is reduced. Thus, the desired load current can be carried in a healthy way. However, this approach increases coil labor and production costs. Here, the number of cores can be reduced together with the decrease in the number of turns. Reducing the number of cores and reducing the number of turns is quite advantageous in terms of cost.