MH&W International has just published a new Information Paper, Incoming Inspection Testing on Soft Ferrite Cores written by Gary Van Schaick (Ferrite Applications Engineer).
Information Paper Introduction
Over the past 30 – 40 years, the applications for soft ferrite and the technology of the soft ferrite has changed considerably. In the 1970s, we were more concerned with ferrites for touch tone telephones, tuned filters and ferrite applications requiring controlled inductance over various temperature ranges. Switch mode power supplies were not well known and ferrites designed for switch mode power supplies were not yet developed. Switching frequencies as they were rarely exceeded 50KHz. Controlling power losses as a function of core temperature was not known. Today, most soft ferrites are used in some power variation of power application and ferrite is being developed to run at 1 – 3 MHz.
And in all this time, the requirement and procedures for incoming inspection has not changed. Paperwork has changed and become more involved, we have seen x‐bar control charts, 6‐sigma inspections and Cpk calculations. But the actual inspection has not changed. In the 1980s, I was responsible for setting up the incoming inspection for many ferrite users. So, this practical guide is based on these years of involvement. I will try to stay away from minute detail but will discuss primarily test conditions including . . .
Download Information Paper(.pdf): Incoming Inspection Testing on Soft Ferrite Cores