Ultra-efficient localized induction heating by dual-ferrite synchronous magnetic field focusing

Induction heating is widely used in aviation, communication, and new energy fields due to its advantages of non-contact, high-power, and controllable heating depth. However, it is still challenging to achieve high energy utilization efficiency of traditional induction heating, mainly due to the magnetic dispersion effect. Herein, a dual-ferrite synchronous focused (DFSF) induction heating method is first proposed by simultaneously placing ferrites inside and outside the induction coil. Meanwhile, an electromagnetic-thermal coupling numerical model was also built to predict the magnetic and temperature fields around the DFSF induction heating system. A conventional induction heating head and two DFSF induction heating heads (cone-type DFSF head and pot-type DFSF head) are compared on soldering the high-power devices. The results show a significant enhancement in magnetic flux density (MFD) with the pot-type DFSF head, exhibiting a remarkable 12-fold increase from 0.02 T to 0.24 T compared to the conventional induction head. Additionally, the pot-type DFSF head generates a substantial 22.3-fold surge in energy within the solder joint, escalating from 0.6 J to 13.4 J, surpassing the traditional induction head. Moreover, the influence mechanism of six external ferrite structural parameters on the heating efficiency was analysed to optimize the pot-type DFSF. It is found that the inner diameter of the ferrite tip has the most significant effect, which can induce a remarkable temperature variation of 310 °C. As a result of optimization, the pot-type DFSF demonstrated an impressive surge of 26% in heating efficiency. Finally, the agreement between the numerical and the experimental temperature proves the accuracy of the model, and the solder joint without defect has been achieved through the pot-type DFSF. This work effectively minimizes the magnetic dispersion and increases the energy utilization efficiency for induction heating, providing new approaches for localized soldering of high-performance power electronic devices.