Current Density Characterization of Litz Wires used in Induction Heating Coils: A Practical Approach

The domain of applications of induction heating system is continuously getting wider. To increase the power transfer efficiency and to reduce the system complexity, in many high-frequency heating applications, the conductor of induction coil is often based on litz wire of suitable size. The flexibility and intensity of cooling of litz-wire based coils is limited, they are mostly air-cooled. The current density of these coils is limited. The transferred power per unit area (power density) by these coils is moderate. Though, they have limited applications, due to low overall cost and increased simplicity of the controller, the popularity of litz wire based induction heating system is getting wider. It is important to practically characterize the most important part of air-cooled induction heating system, i.e., the litz wire conductor based coil. This article explores a method to practically demonstrate the permissible current density of different types of litz wire based coils used in induction heating applications.