Micrometals iron powder cores have an organic content and undergo thermal aging. When cores are exposed to or generate elevated temperatures, a permanent decrease in both inductance and quality factor (Q) will gradually occur. The extent of these changes is highly dependent on time, temperature, core size, frequency, and flux density. It is essential that these properties are considered in any design operating at or above 75ºC. Iron powder cores tolerate temperatures down to -65ºC with no permanent effects.
In high power applications where core loss is contributing to the total temperature, a decrease in quality factor will translate into an increase in eddy current losses which will further heat the core and can lead to thermal runaway. Designs where core loss exceeds copper loss should be avoided. Hysteresis losses are unaffected by the thermal aging process.
A detailed thermal aging discussion can be located in application notes section of this website, also thermal aging predictor has been incorporated into our inductor design software. Please do not hesitate to contact our application engineers for specific application questions and free design consultation at Applications@Micrometals.com.