Peak an inductor actively?

Question

I want to peak an LC circuit as the load changes. It's < 30 KHz and the inductor is approx 20 mH.

I've seen some patents for electrically-controlled inductors (one winding is the control winding) which changes the permeability of the core. But I've not found any such designs used or offerings on-line.

I would appreciate any constructive suggestions how I might go about this.

Janey

Adrian C · Accepted Answer

Not an inductor but use a gyrator?-- Adrian C

Terry Given · Answer

go read some ancient books on magnetic amplifiers; Geyger & Storm are both very good.

this stuff is old. so old that it hasnt been mentioned in universities for decades (except for using mag-amp post-regulators on smps), so I wouldnt owrry about any patents.

Cheers Terry

John Fields · Answer

---JF

John Fields · Answer

---What's your application?JF

Phil Allison · Answer

"Janey"** Be a hell of a lot easier to vary the drive frequency to bring the LC circuit into resonance. Just needs a detector to indicate when the voltage and current are in phase......  Phil

Janey · Answer

If that were the goal, yes. But I want to peak a given frequency. How would one go about this detection?J.

John Fields · Answer

---Easiest way: (View in Courier:)                   29KhZ                   /       +----------+       |          |       |         [L]       |          |  [GENERATOR]     +---------+       |          |         |       |       [1.5nF]   [SCOPE]       |          |         |       +----------+---------+       |      GNDTune the inductor and when the voltage on the scope peaks that'll bewhen current and voltage are in phase.BE CAREFUL!!!  Depending on the Q of the circuit and what what the generator lookslike,  the voltage at the junction of the L and the C could be lethalto you or to whatever it's connected to.What's your application?JF

John Fields · Answer

---PS:Version 4SHEET 1 880 852WIRE -1024 272 -1088 272WIRE -912 272 -960 272WIRE -816 272 -912 272WIRE -1088 320 -1088 272WIRE -912 320 -912 272WIRE -816 320 -816 272WIRE -1088 448 -1088 400WIRE -912 448 -912 400WIRE -912 448 -1088 448WIRE -816 448 -816 400WIRE -816 448 -912 448WIRE -1088 512 -1088 448FLAG -1088 512 0SYMBOL voltage -1088 304 R0WINDOW 3 24 104 Invisible 0WINDOW 123 -70 109 Left 0WINDOW 0 -68 67 Left 0SYMATTR Value SINE(0 1 29000)SYMATTR Value2 AC 1SYMATTR SpiceLine Rser=50SYMATTR InstName V1SYMBOL ind2 -928 416 M180WINDOW 0 -50 70 Left 0WINDOW 3 -68 39 Left 0SYMATTR InstName L3SYMATTR Value 20e-3SYMATTR Type indSYMATTR SpiceLine Rser=1SYMBOL cap -960 256 R90WINDOW 0 -40 28 VBottom 0WINDOW 3 -38 29 VTop 0SYMATTR InstName C1SYMATTR Value 1.5e-9SYMBOL res -832 304 R0SYMATTR InstName R1SYMATTR Value 10e6TEXT -1080 472 Left 0 !.tran 0 .0033 .003 uicTEXT -1080 496 Left 0 !;ac oct 512 10000 50000JF

Janey · Answer

The basics of designing a saturable reactor is:

wind a 3-winding inductor (or two 2-winding inductors) - design for a uH/mH value greater than your greatest need
wire the "business" windings in series
apply a DC voltage to the control winding(s) and adjust such that the sum inductance in the main windings reduces and approaches your target.

The inductance will be maximum with minimum control voltage, and vice versa.

Is this right?

Janey

Peak an inductor actively?

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