Surplus electricity

Mar 18, 2026 Last reply: 3 months ago 136 Replies

back when I first learned about them - back in 1970 - they didn't.

The wikipedia article you are presumably relying on does talk about "T-shaped sections" for specialised applications, but doesn't suggest that this is what is usually meant.

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I make a habit of it. You didn't post the link you seem to have been relying on, and and you don't seem to have learned as much from it as you might have done. Your claim that the metalisation can be an aluminium/zinc composite strikes me a dubious. The metalisation can be either aluminium or zinc, but putting both down on the same film does seem to be improbable. Metal-spraying the ends of a capacitor with finely divided molten zinc to connect the aluminium films to real wires does seem to happen.

The self-healing properties of evaporated metallic films does imply the films are made as thin as they can be - which is to say just thick enough that the thinnest areas are just one atom thick. I should ahve thought of earlier - I've known about self-healing forever, but don't get to think about it all that often.

You are allowed to look that up and learn.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Except in this case where you are clearly unable to do so.

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If the AI summary doesn't appear click AI mode.

You might also try this:

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Since it's more suited to an individual who disdains others without a PhD.

You advanced the proposition - it's up to you to find the evidence to support it.

This is actually the informative link.

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It seems that in some applications it is worth putting down an initial - very tin layer of aluminium to give a somewhat thicker layer of zinc, something that is easier to bond to than bare plastic film. The link does make the point that zinc films self-heal better than aluminium films - it takes less energy to blow it away from the short-circuit path

- but they do oxidise at room temperature in way that alumniuum films don't.

Plowing through papers published in peer-reviewed journals in one of the tedious tasks one has to master to get a Ph.D. I don't think that that link is any more useful than the one I've picked out of your first grab bag.

I don't disdain people who haven't got a Ph.D. Win Hill started on a Ph.D. in chemical physics, but he had better supervision than I had and they persuaded him to get a masters degree in electronics instead.

I am a bit disdainful of people who can't write a concise post that says what it needs to say. Academics should be able to manage this, but many can't, and it is skill that many have master without getting any academic training>

Not a bit.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Told ya so.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

More unwilling than incapable. Educating you is a thankless task, in large part because you don't show any sigh of getting educated by exposure to more detailed information.

You didn't. You made a bald claim unsupported by any evidence. You did post a link that presented a whole grab-bag of possible sources, but you didn't identify any of them as actually useful, so you didn't tell me anything. Even the sloppy nature of your thinking that this revealed (again) has been on show for the past twenty years.

Yes he did.

LOL

Eb Major has three flats. I can find evidence if you want but I don't provide evidence for every statement I make because others can either find out for themselves or they may already know.

In your ever-so-expert opinion.

Edward Rawde is easily amused.

John Larkin made vague and unsupported claims about aluminium and zinc metallisation in plastic film capacitors. He did - more or less accidentally - came up with a link to more specific information, but he didn't highlight the link in any way or indicate what the specific information meant.

It is perfectly true that any of us might have come up with that for ourselves if we had looked hard enough, but in this particular instance he didn't look very hard. He rarely does.

I think I remember getting a response like that on a different subject a few years ago. From a teenager.

Some teenagers are pretty good at recognising childish responses.

Weren't we having a conversation here?

Something about power conversion (and inversion), ..., not so much the "projection".

"Chivalry's not dead / it's just curled up / weakly kicking in the corner / with Courtesy and Conversation."

Yes but then Bill arrived. I'm done with this.

That makes life more enjoyable. Are you ever amused? Certainly not here.

I said that film caps do not use single-atom thick metalization, and that some use combined aluminum and zinc metalization. I learned those in a few minutes of web searching.

It wasn't hard to find facts about metalization. The mystery is why you couldn't.

I wonder how really big caps are constructed, like the utility power-factor things.

I used to buy huge oil caps when I was a kid, to pop flashtubes or just make loud noises. I'd run them at all the voltage I could make, like 25 KV.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It had drifted into the metalization of film capacitors.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Some of us were, then Edward Rawde horned in. Like John Larkin, he expects more respect than he deserves, and is resentful about not getting it.

He injects himself into the conversation, gets rebuked and retreats in a tiff.

The thread warped into an discussion of metallised film capacitors. You had posted a daft idea about making compact high value capacitors by effectively crumpling up the opposed surfaces as matching beds of nails, ignoring the fact that spikes generate field emission current.

Arc discharges depend on this fact - the discharging surface gets hot enough to distort into lots of small but very sharp spikes when subjected to a high electric field.

<snip>

Common interests are wide and varied, everybody has a unique and distinct perspective.

There's something to appreciate from all the contributors, better than the usual dead-internet bot-net, and often enough a gentle barb is appreciable a smooth jibe, then for the gentlemanly, scholarly, and professional.

"Don't argue with a pig, both get dirty and the pig likes it." "Don't argue with stupidity, it gets stupid and they have lots more experience."

Trapping and dispatching trolls is a common enough exchange in plain unmoderated open forums of the voluntary sort.

I respect elders, even old farts, or as Mark put it one time upon retirement, "now I'm retarded".

It reminds me of the chemistry instructor's lab-coat buttons, "old age and experience beats youth and vigor", or, the old "hydrogen cyanide is all natural".

Aye, it's a simplest sort of idea of an ideal super-capacitor, then about the why's and wherefore's.

I certainly could have done, but you'd made the claim - why should I bother? When I looked at one of the several links you'd posted, I was able to dig out a tolerably coherent exposition of what was actually going on, and posted it, which you hadn't done.

If you had read the link you posted, you'd have found out.

The problem with very high voltage differences is that you get corona discharge, so you have to limit the voltage over individual gaps to less than about 100V. If you just stack your film layers you can do that.

There's no explicit DC path between the successive layers, but the leakage current rises rapidly (and quasi exponentially) with voltage and the leakage currents adjust the DC gradient to a nice even distribution between layers.

The fluid used to fill them was a nasty halogenated hydrocarbon. It got phased out decades ago on health grounds.

Sulphur hexafloride is even better at damping out arc discharges, but it is remarkably potent greenhouse gas.

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