Comparative analysis and improved design of LLC inverters for induction heating

Abstract

Abstract This work presents a comparative analysis and design procedure of a converter based on an LLC resonant inverter used for induction heating applications depending on the transistor technology used and the selected operating frequency. A major objective of the work is to determinate the inverter design requirements leading to the optimal sizing of the components, improving its operation and minimizing power losses. Additionally, it proposes a design to obtain a great insensitivity of the inverter operation against large variations of load impedance. This article analyzes the operation of the inverter where the power regulation is carried out by phase‐shift (PS) modulation. Simple rules are formulated for the design of the resonant circuit components. The design has been verified testing a 25‐kW inverter in an industrial application of induction hardening operating at 500 kHz. Inverter efficiency is around 98.5% when using Silicon Carbide (SiC) MOSFETs.

Keywords

• induction heating
• phase shifters
• power conversion
• power MOSFET
• resonant power convertors