Increasing Inductor Lifetime by Predicting Coil Copper Temperatures

摘要

In recent years, there has been a significant increase in the customer demands for improved induction coil lifetime. This has led to several publications in recent years by induction tooling manufacturers The main conclusion in these papers is that besides mechanical crashes the cause of most induction coil failures is localized overheating of the coil copper due to insufficient cooling. What is lacking from these publications is any way to determine what is sufficient cooling. In this paper, a scientific method for determining local copper temperatures will be presented. This will include evaluations of heat transfer coefficients for different sections of a multi-component inductor, dependence of heat transfer coefficient on water pressure and water passage cross-section, non-uniform power density distributions in various 2-D cross-sections and the resulting temperature distribution in the copper winding. The effects of duty cycle on optimal design will also be considered.