The subject of this posting is inductance variation with DC bias. The facts: #1. "Initial Permeability vs. DC Magnetizing Force Graph" is very common curve. It has same shape as inductance vs. DC bias at small AC excitation. (*) #2. I measure inductance by applying DC voltage to the coil and recording the current, L=3DV/(dI/dt). I have no other way to get 60+A DC bias. The result is somewhat similar to (*) above. Only somewhat. The inductance values may differ 30-40% (powder core Al tolerance is
10%). #3. I get same (L=3DV/)dI/dt) ) result by analyzing "real life" waveform (60ADC bias, 30Apk-pk, ~100kHz triangular ripple) #4. There is also a hump at the beginning of the plot (L vs. I) that reminds "Percent Initial Permeability vs. Peak AC Flux Density Graph"my assumptions: The method I am using (L=3DV/(dI/dt) ) is neither (*) - considering single point at B-H curve, one at at time. nor (**) - symmetrically (relative to zero) driving along B-H curve with increasing amplitude. Questions: Q1. What is the physics behind this "hump":