All-metal domestic induction heating using single-frequency double-layer coils

In the past few decades, induction heating based on near-field magnetic coupling has been actively developed, aiming to improve the efficiency, controllability and safety. For traditional induction heating, the heating coil is energized by an AC power source to generate an alternating magnetic field, which in turn induces the eddy current in the workpiece to produce the heating effect [1]. Nevertheless, the workpiece made of non-ferromagnetic materials like stainless steel, aluminum and copper cannot be properly heated, which dramatically limits its application as compared with traditional open-fire heating. There was an attempt to heat the non-ferromagnetic workpiece using a strong magnetic field provided by superconducting windings [2], but it was not practical for domestic induction heating. By using low-frequency AC (around 20 kHz) to heat the ferromagnetic pan and high-frequency AC (over 70 kHz) to heat the non-ferromagnetic pan, the selective operating frequency technique was developed for all-metal domestic induction heating [3]. However, the corresponding switching and winding losses significantly increased, which inevitably resulted in low heating efficiency. In addition, the frequency selection caused serious electromagnetic interference and increased complexity and cost. Recently, the homogeneity and flexibility of induction heating has been improved by adopting the magnetic resonant coupling (MRC) mechanism [4]-[5]. In this paper, a new all-metal domestic heating system is proposed and implemented. The key is to employ double-layer coils and utilizes the MRC mechanism to induce a high current in the resonant coil when heating the non-ferromagnetic pans, thus successfully heating both the ferromagnetic and non-ferromagnetic pans at 30 kHz resonant frequency. Consequently, the advantages of simplicity, high heating efficiency and single operating frequency can be attained for all-metal induction heating.