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Arbitrary (saturable) coupled inductors in LTSpice

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emece67:
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uer166:

--- Quote from: emece67 on July 03, 2019, 11:57:46 am ---May I ask about the geometry of the core you are modelling?

--- End quote ---

It's a simple ungapped toroid. I just use the cross section area and magnetic path length in my simulation. The cores I'm looking at are made by winding a very thin strip of Nickel-Iron or Cobalt-Iron alloy onto a bobbin, I'm assuming to decrease eddy currents, although I presume there is still current flowing in loops in sort of a planar fashion in the metal..

emece67:
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uer166:
Sort of, I'm trying to select appropriate cores and basically specify the "ideal" values. I need as high permeability as possible in the Hc regions to make the measurements easier. What's core conductivity? you mean electrical conductivity to calculate eddy current losses? Unfortunately no idea on this one.. Maybe I can take it apart and see, but I know these are very thin (double digit microns?) Nickel or Cobalt-iron tape wound cores.

As an update: so far so good! First prototype current meter with a Toshiba core has a DC offset of about 200uA, can measure +-150mA with 2KHz bandwidth, or 20KHz bandwidth if I do less filtering in DSP, at the expense of some noise which would still be less than 1mA RMS. Attached is me manually putting some DC current through core using a power supply with approx. values. and seeing the output. Error is around 0.1% at 20mA which is wayyy better than expected.

Also the scope trace are the 2 coil currents of the self-oscillating core, and the ADC sampling ISR in yellow.

uer166:

--- Quote from: ahbushnell on June 26, 2019, 12:03:40 am ---Looks linear.  Have you tested in the nonlinear region?  Validated with real parts? 

--- End quote ---

I did now!

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