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Peak an inductor actively?

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

Reply to
Janey
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Not an inductor but use a gyrator?

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Adrian C
Reply to
Adrian C

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

Reply to
Terry Given 

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http://www.google.com/search?hl=en&q=saturable+reactor

JF
Reply to
John Fields 

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What\'s your application?

JF
Reply to
John Fields

"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

Reply to
Phil Allison

If that were the goal, yes. But I want to peak a given frequency.

How would one go about this detection?

J.

Reply to
Janey

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Easiest way: (View in Courier:)

29KhZ / +----------+ | | | [L] | | [GENERATOR] +---------+ | | | | [1.5nF] [SCOPE] | | | +----------+---------+ | GND

Tune the inductor and when the voltage on the scope peaks that'll be when current and voltage are in phase.

BE CAREFUL!!!

Depending on the Q of the circuit and what what the generator looks like, the voltage at the junction of the L and the C could be lethal to you or to whatever it's connected to.

What's your application?

JF

Reply to
John Fields 

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PS:

Version 4
SHEET 1 880 852
WIRE -1024 272 -1088 272
WIRE -912 272 -960 272
WIRE -816 272 -912 272
WIRE -1088 320 -1088 272
WIRE -912 320 -912 272
WIRE -816 320 -816 272
WIRE -1088 448 -1088 400
WIRE -912 448 -912 400
WIRE -912 448 -1088 448
WIRE -816 448 -816 400
WIRE -816 448 -912 448
WIRE -1088 512 -1088 448
FLAG -1088 512 0
SYMBOL voltage -1088 304 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 -70 109 Left 0
WINDOW 0 -68 67 Left 0
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SYMATTR Value2 AC 1
SYMATTR SpiceLine Rser=50
SYMATTR InstName V1
SYMBOL ind2 -928 416 M180
WINDOW 0 -50 70 Left 0
WINDOW 3 -68 39 Left 0
SYMATTR InstName L3
SYMATTR Value 20e-3
SYMATTR Type ind
SYMATTR SpiceLine Rser=1
SYMBOL cap -960 256 R90
WINDOW 0 -40 28 VBottom 0
WINDOW 3 -38 29 VTop 0
SYMATTR InstName C1
SYMATTR Value 1.5e-9
SYMBOL res -832 304 R0
SYMATTR InstName R1
SYMATTR Value 10e6
TEXT -1080 472 Left 0 !.tran 0 .0033 .003 uic
TEXT -1080 496 Left 0 !;ac oct 512 10000 50000

JF
Reply to
John Fields

The basics of designing a saturable reactor is:

  1. wind a 3-winding inductor (or two 2-winding inductors) - design for a uH/mH value greater than your greatest need
  2. wire the "business" windings in series
  3. 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

Reply to
Janey

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