Temperature Control for Automated High Frequency Core Loss Testing

This paper describes challenges to automated bulk collection of temperature-controlled magnetic core loss data in the 1-20 MHz regime. Oil immersion is shown to alter the small-signal impedance of ML91S and FR67 ferrite cores by more than 5% over part of their rated frequency ranges which prevents accurate estimation of core loss. Air-based thermal forcing is shown to be a viable alternative to oil for core temperature regulation in high frequency core loss testers. Temperature regulation to 25 ± 3°C is demonstrated on FR80 at 1 MHz up to 1.25 W of dissipation.