I've increased the cross section of the air about ten 10 times, and for this value, both Inductances match (the one I calculate and the one I measure). Could this mean that 600Hz is the best test frequency and consequently the operational frequency? I've runned some parametric tests with the LCR meter and the Quality Factor, Q, is maximum at 600 Hz, and the Inductance measured is still 14,21. Since this value seemed to be the one driving the equation, I suspect it's your problem child. I'm not sure of the proper way to figure it, but I'm sure it's bigger than the ferrite. It's my (admittedly weak) understanding that different ferrite mixes are designed to operate at different frequencies, so the specified permeability may be off at 20Hz.Īlso your air cross section is way off. It's also important to say that the wire is wounded in 7 layers in each leg (like 7 coaxial solenoids overlapped). My wire is not very tightly wounded, with 200 turns in each leg. And no, I've not considered fringing not any Reluctance related to any leakage flux.Ĭould this justify the difference between the measured Inductance and the one I've calculated? I've considered a cross section of air equal to the cross-section of the ferrite but it could have been a bad consideration. The cross section of the ferrite core is 28mm*30mm = 8,4 e-4 m 2. What's the diference between the test frequency and operational frequency? I'm using an Agilent E4980AL (link to the manual: ) with a test frequency of 20Hz.

The ferrite type is N47 (Siemens N47) with a relative magnetic permeability of 1020.

Ferrite inductor calculator