Study On Secondary Series Resonant Induction Heating Power Supply

The induction heating power supply, with the advantages in many aspects such as low pollution, high efficiency, rapid heating, convenient control, production safety, is applied widely in the field of black metal heat treatment. Based on the above advantages of induction heating power supply, induction heating technology is gradually being introduced to the industrial production of the non-ferrous metal heat treatment. However, because of the physical characteristic that the non-ferrous metal usually has low magnetic conductivity, there will be some problems in the design of power supply.This thesis takes the secondary series resonant induction heating power supply as the research object. Through the analysis and comparison between the primary series resonant topology and the secondary series resonant topology, we derived that there are advantages in the secondary series resonant topology when it is used in the non-ferrous induction heating applications based on the theories. Lastly, we drawn the conclusion that the secondary series resonant topology is more suitable for non-ferrous metal induction heating power supply.Generally, in the non-ferrous metal induction heating applications, the resonant network of the power supply has a higher quality factor. By using the secondary series resonant topology, it can achieve the following two objectives effectively:I. It can reduce the voltage of the source of the resonant network, and the operating voltage of the energy storage devices that comprise the resonant capacitor and the transformer primary effectively.II. It can reduce the volume of the transformer, and decrease the occupied space of the power supply effectively.In addition, in order to cope with the problem of the high frequency transformer magnetic flux saturation when using the secondary series resonant topology, this thesis put forward a new kind of pulse density modulation(PDM) mode and concluded that the magnetic flux saturation phenomenon does not appear in this mode from the theoretical analysis.In this thesis, the scheme of secondary series resonant topology based on PDM is used in the induction heating power supply for non-ferrous metal heat treatment. The power supply was designed at 20~40k Hz/1k W, by using the IGBT as the power switch tube. We use SG3525 as the core component of control circuit. This thesis designs and analyzes several functional modules in detail, including the inverter’s working process, the modules of frequency tracking, power condition, swept frequency start, fault detection and switch drive.Finally, the author made a principle verification prototype. This thesis analyzes the experimental wave forms and the related theories comparatively. The experimental phenomena shows that the application on non-ferrous metal induction heating of in this project research is feasible.