Ferrite AC Inductor Design Approach

Thread Starter


Joined Jun 11, 2012

I was wondering if someone might be able to point me in the direction of designing a custom inductor, this is something I’ve never dreamed of, and unfortunately, I don’t recall doing much electromagnetism throughout my degree, which looking back is a shame.

Over the last couple of weeks I’ve been working on part of a resonant tank circuit formed by a series LC circuit. The C element is fixed due to a piezoelectric ceramic intrinsic capacitance, so at a specific drive frequency I need to cancel the C element as to reduce/eliminate reactive power.

I’ve shortlisted the specification for the inductor that I need to prototype, and I’ve found the manufacture of cores who will construct several units for me… However, no matter how many books and papers I’ve read – none have cleared my mind as to how to go about designing a Ferrite AC inductor, none of the papers have a standard approach to design, and formulas jump from SI to CGS system to Window Area Product, and as far as I can follow this is an iterative process which needs experience and trial and error… I think I get the basics, but I need help with a methodical approach, can anyone help?

Inductor Requirements
· Inductor value: 846µH ±10%
· Operating Frequency: 20kHz to 50kHz (35kHz_Typ)
· Operating Voltage: 500Vrms_Max (200Vrms_Typ)
· Continuous AC Current: 1Arms_Max (0.35Arms_Typ)
· DC current: Nil
· Operating Ambient Temperature: +25°C ±10°C
· Permitted Inductor Temperature Rise: +80°C
· Preferred wire construction: Litz
· Core: Ferrite R, or P material
· Core shape: Preferred core geometry: Pot Cores, E, ER, EC, ETD, EER – but open to suggestions
· Physical size constraint: Ideally < 50mm3 (but not critical)