Variable inductor in LTSpice

See "Inductor_with_Saturation.zip" on the Device Models & Subcircuits page of my website for the basics of making a variable inductor. This particular model is current dependent but can be adapted to voltage control. ...Jim Thompson

"VControlledCap.zip" on that same page may give you further information on how to make a voltage-controlled inductor. ...Jim Thompson

Thank you. It doesn't solve my problem, but at least I know where to start. In the case of a resistor it is very simple, but the solution does not apply to the remaining passive components. Why is it so damn hard?

My goal is to simulate magamps in the far future, but after the initial experience with the saturable core reactor I am not even sure that LTSpice is the correct tool. Do you know of something better suited for this task and still free, as it is pure hobby?

Best regard, Piotr

An inductor gives v=L*di/dt. Now, I suppose you want a box where the proportionality constant is L=L(Vc).

The idea is as follows:

1. Create a circuit where V1=1*di/dt. This means, measure i, copy it with a CCCS to another place, feed it to an 1H inductor and measure the voltage V1 across its terminals.

1. Copy this voltage to the box port with a VCVS with the desired gain: V= (Ao*Vc+A1*Vc^2+...)*V1 (Assuming a polynomial is ok for you, a POLY statement is the way to go)

You may apply this creatively!

Pere

That's only because Mike Engelhardt made a special resistor model in LTspice that performs that function.

It's not. "o pere o" is sort of on the right track (Message-ID: )...

Stack an inductor and a voltage-controlled voltage source which has two inputs: the voltage across the inductor and a control input such that the output is K*V(L). Thus acts as an inductor of value (K+1)*L

I'll post a model to my website later today.

...Jim Thompson

See "VoltageControlledInductor.pdf" on the Device Models & Subcircuits page of my website. ...Jim Thompson

Oooops! Left off 2*pi :-( ...Jim Thompson

For saturation, you might start with something like this:

• Saturable Core Model, copied from:
• _SPICE Models For Power Electronics_, Meares and Hymowitz.
• .SUBCKT INDSAT 1 2 PARAMS: VSEC=1e-4 LMAG=1e-5 LSAT=1e-7 FEDDY=1e6 F1 1 2 VM1 1 G2 2 3 1 2 1 E1 4 2 3 2 1 VM1 4 5 0 RX 3 2 1E12 CB 3 2 {VSEC/500} IC=0 RB 5 2 {LMAG*500/VSEC} RS 5 6 {LSAT*500/VSEC} VP 7 2 250 VN 2 8 250 D1 6 7 DCLAMP D2 8 6 DCLAMP .MODEL DCLAMP D(CJO={3*VSEC/(6.28*FEDDY*500*LMAG)} VJ=25) .ENDS

It might be reasonable to add some sort of current steering function to the input, so that it has hysteresis.

Typical usage of this model is: specify the PARAMS as for one winding of a transformer, then build the rest of the transformer using ideal transformers and leakage inductors.

Playing funny business with the core geometry (orthogonal loops of core, CM/diff winding arrangements) might be possible using two of these and appropriate coupling, or may need additional modeling, I'm not sure.

Tim

See... "Inductor_with_Saturation.zip" on the Device Models & Subcircuits page of my website. Highly accurate and easy to fit to measured data. I developed that model a few years ago when I encountered such a beast being used as a spacing sensor for a heavy truck clutch ;-)

So far modeling the hysteresis has evaded me.

...Jim Thompson

Jim and all, thank you very much for your help!

Best regards, Piotr

You are quite welcome! ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at