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Old 1st February 2004, 08:06 PM   #1
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Default Power supply inductors

I have been unable to find air core inductors suitable for use in a CLC power supply. Most are intended for use in loudspeaker crossover units and are wound on plastic bobbins - i don't trust that they will be robust enough to sustain continuous high DC current of 6amps or more without becoming hot and a potential fire hazard.

The reasoning behind my thoughts is that with a typical DCR of 0.5 ohms or more and a current of 6amps i'm looking at dissipating 18 watts and have doubts about doing that on a plastic spool.

Does anybody know of a source for suitable inductors (preferably in the UK)?
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Old 1st February 2004, 08:35 PM   #2
Magura is offline Magura  Denmark
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I make custom air core inductors up to around 100mH.

You can have pretty much any configuration of materials you please.

If interested, email me.

Magura
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Old 2nd February 2004, 08:27 AM   #3
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Default Looking for something more "off the shelf"

Thankyou for your offer, but custom winds and shipping from Denmark doesn't sound like a cheap option for the quantity i'll require.

My brother in-law winds inductors as part of his job, but it will ultimately cost me more (i.e. i'll owe him a favour and end up labouring for a couple of days building his house extension), so i was looking to see if something more readily available could be found.

I was after 2.2mH, 1.5mm wire and DCR 0.5 ohms air core inductor.
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Old 2nd February 2004, 08:47 AM   #4
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Um... why aircore?

And in a wider sense... I've always wondered why SS amps use just C, or CRC power supplies, while tube amps are seemingly decades ahead in PSU effectiveness with our use of small, efficient caps and hum-cutting chokes. Really makes 'ya think.

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Old 2nd February 2004, 09:15 AM   #5
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Default Why aircore?

In a tube amplifier you draw very little by way of current, so you need little by way of capacitors and have nothing to worry about with choke core saturation, etc.

Solid state pulls many amps, readily saturates small inductors and needs capacitors the size of baked bean cans.

Different problems, different solutions...
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Old 2nd February 2004, 03:16 PM   #6
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A 100W tube amp consumes 200W just as much as a 100W class AB solid state amp consumes 200W at full output. There is no difference. For an amp this size I would expect the choke to run a good 3" x 2-1/2 x 2-1/2" overall dimensions. (In a tube amp, this would be offset by the rather large OPT and slightly-larger-than-SS-amp's PT, probably leading to some of this confusion.) If you know the equations, current, voltage, resistance and required inductance and capacitance for the filter are related such that voltage and current tend to be exchangable. A 50V 4A supply is about the same size at a 500V .4A supply.

It seems to me that thousands of people go through classes just hearing rumors of large inductors, and perhaps only using a few RFC's in RF circuits. As SS phased out tubes, so have excessive capacitance, resistance and regulators phased out power supply chokes.

Wait a minute, that sounds like a rant

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Old 2nd February 2004, 03:29 PM   #7
KBK is offline KBK  Canada
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That's fine.. I hear you! As for SS amps with chokes... methinks it would be a good thing, considering that bandwidth in audio gear takes them away from any simple power factor calulations. The trick is getting good nough transformers and chokes. I, for one, would only look at plitron chokes, if I could afford it.
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Old 2nd February 2004, 03:31 PM   #8
Magura is offline Magura  Denmark
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Default Re: Looking for something more "off the shelf"

Quote:
Originally posted by Jason Hubbard
Thankyou for your offer, but custom winds and shipping from Denmark doesn't sound like a cheap option for the quantity i'll require.

.

I was after 2.2mH, 1.5mm wire and DCR 0.5 ohms air core inductor.

Its something like this youre after...right??

custom heatsink machining

In that case i can tell you that there is no off the shelf solution.

Ive made a few of them for that reason.

Magura
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Old 2nd February 2004, 04:54 PM   #9
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Hi Jason,

Here are 2 examples of companies that could supply what you looking for. The companies are Solen (which I'm using) and Jentzen.
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Old 2nd February 2004, 05:19 PM   #10
Magura is offline Magura  Denmark
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my mistake....i thought off the shelf ended at 2mH....it sure does in this end of the world.

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