Abstract
The paper explains the operating principle of an LLC resonant circuit for induction heating applications. Although induction heating has attracted a great deal of attention in recent years, very little consideration on designing the inductor in the resonant circuit for specific requirements has been done. Specifically, a design procedure with the required power and work-head dimension as inputs is still needed, from a practical point of view. In this paper, a quantitative analysis of power transferred to the work-head will be done to help design the resonant circuit. A design procedure for the LLC circuit will be proposed, utilizing results from the quantitative power analysis and taking into account mechanical constraints on the work-head. In addition, a simple technique to monitor the soft switching condition of the power switches in the resonant inverter, utilizing only voltage signals, is also proposed. The feasibility of the proposed design procedure will be demonstrated and verified by simulations and experiments.
Highlights
Induction heating makes use of high frequency inverters, in which a resonant circuit is formed by a work-head and a capacitor in series 1–4 or parallel configuration 5
Induction heating has been an advanced process for industrial quenching applications, aiming to increase the material's hardness to a desirable depth of penetration, with advantages such as high energy conversion efficiency, clean, safe and especially localized heating
An L coil with the right shape and size for the material to be heated will be normally used, and the matching between the coil size and the quenched material has a great effect on heating performance as well as the operation of the power converter, because it affects the airgap in the electromagnetic-thermal energy conversion system
Summary
Induction heating makes use of high frequency inverters, in which a resonant circuit is formed by a work-head and a capacitor in series 1–4 or parallel configuration 5. A design procedure for LLC resonant circuits (in induction hardening) will be proposed, taking into account work-piece dimension and ZVS conditions. Input parameters for designing the RF induction heater include: Desired dimension of the work-head (parameters a, b, and n), heating power P (depending on heating temperature and time), DC link voltage, operating frequency f0 (depending on skin depth), and variation range of the quality factor of the work-head and work-piece ([Qmin, Qmax)]. On the other hand, switching angle in LLC resonant circuits should be smaller than 20O 11, : Ln = 6 × tan (20o) − 1 = 1.18 From this ratio and the inductance value calculated in step 1, series inductance Ls can be determined: Ls = 1.18 × 2.1 ≈ 2.4 μH (13). Table. 1 summarizes all design parameters for the demonstration system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Science & Technology Development Journal - Engineering and Technology
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
