## General

#### Why is AL inductance calculation results in Maxwell and PEmag different?

• FAQ
Participant

For example the Maxwell 3D file has a core permeability of 1400 (approx) and the total energy gives an equivalent inductance of 100uH (approx). PEmag assigns to the core an effective permeability mu based on the AL value (the manufacturer says AL = 800 nH/turn^2). mue = AL*le/Ae/mu0 = 800e-9*19.3e-3/11.3e-6/(pi*4e-7)= 1087.32 So value in PEmag is lower than the one from Maxwell. Thus total energy in the Maxwell 3D simulation gives 78uH. There is a workaround, modify by hand the AL value in PEmag as follows: AL = mu*mu0*Ae/le = 1400*pi*4e-7*11.3e-6/19.3e-3 = 1030 nH/t^2 and you will get the desired values. PExprt uses an AL value similar to the one suggested by the manufacturer of the core. It is a good idea to keep doing it because we follow the manufacturer recommendations. Take into account that this AL (or permeability) can have a very high tolerance (+-25%) and it is directly reflected in the inductance value for non-gaped designs. Ferroxcube gives for clients core AL = 800 nH/t^2. So, L = 800*10^2 = 80 uH But it could be: L = 1.25*80 = 100 uH or: L = 0.75*80 = 60 uH Using a gapped component will minimize this variation, since the inductance depends primarily on the air gap and the AL tolerance effect is diminished.