Hey,

I have got two sets of E70/33/32 core of N87 material, one set with centered airgap of 8mm and another set is un-gapped core. I measured the inductance for N number of turns with centered gapped core and also I measured the inductance with 4mm airgap in the each leg (which gives effective airgap of 8mm). But I am getting different inductance value in both cases, for higher number of turns I am getting difference of 1 to 1.5uH. I am getting more inductance for distributed gapped core. I do not understand the reason behind it. I designed my own coil former(bobbin) just to give 4mm airgap in each leg and also tried putting a plastic of 4mm on each leg and measured it but the inductance is different in both the cases. I would want to go with distributed air gap because of its advantage. But I would like to know what is the reason to have different inductances in both the case. If anyone has experienced this please let me know.

 

Maybe this will help - https://www.powerelectronics.com/content/article/21861299/why-have-an-air-gap