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Artefact in the John Chad model of a hysteretic inductor in LTSpice

I've used this model to simulate a real - gapped - inductor in a test circuit, and it seems to work.

In a more complete simulation, it seems to inject 1mA current steps from time to time - my simulated data is littered with 1nC charge pulses from a nominally 1.44mH simulated hysteretic inductor.

Has anybody got an alternative - better behaved - formulation of the model or a work-around. Embedding the simulated inductor in a filter network doesn't seem to help - or not at least for a filter network that won't impair the fidelity of the simulation.

The inductor I'm simulating is an EPCOS RM14 cores with a 1.9mm air gap and an Al of 160nH per root turn.

The Spice data is "HC=20. Bs=.49 Br=.18 A=0.00017 Lm=0.07 Lg=0.0019 N=95"

In the Spice netlist

"L20 N034 N039 HC=20. Bs=.49 Br=.18 A=0.00017 Lm=0.07 Lg=0.0019 N=95"

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman
Loading thread data ...

0.0019
19 N=3D95"

Sorry. False alarm. The current spikes were coming from another part of the circuit - the OPA27 has input protection diodes, and the current was coming from there.

It's embarrassing that it took as long as it did for the penny to drop.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

0.0019
19 N=3D95"

haven't used this form, but will check.

why not post the .txt form of the .asc file?

Reply to
Robert Macy

=3D0.0019

0019 N=3D95"

Since my much cleverer friend in London didn't recognise the trick I was using (which I invented back in 1975 and haven't used since then) it may be patentable, which kind of discourages open publication.

In any event, there doesn't seem to be anything wrong with John Chad model, and I've fixed the real problem in my simulation, which is not crunching away very, very slowly - 100psec per second when I last looked - though it has started to pick up speed. It should go faster once the circuit settles down into the start where it's doing what I want it to, but start-up can be a bitch.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

g=3D0.0019

0.0019 N=3D95"

doesn't .tran 0 1 UIC .IC n1=3D1 n2=3D3 .... and current through inductors on their line help?

Reply to
Robert Macy

Why should it be embarrassing ? You should be used to that by now!

Jamie

Reply to
Jamie

st

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r

Lg=3D0.0019

=3D0.0019 N=3D95"

Less than you'd think. I've tried setting the initial current through the inductor at 50mA (roughly it's peak value when the circuit settles down0, and the routine that sets the initial DC conditions reduces the actual starting current to microamps when I'm using the John Chan inductor model.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

=3D0.0019

0019 N=3D95"

I've got delusions of competence.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

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