Matching to the impedance of an alternator.

Series operated Crees seems popular judging by what I've found searching, but I was thinking along the lines of a single Cree and a current controlled buck - I may even consider a made for that chip.

Reply to
Ian Field
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Using an SCR as a shorting regulator is actually common.

John

Reply to
John Larkin

you'll want to look up solar power circuits,

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

Thanks, I'll have a search on that when I've done twawling the candlepower forums that was suggested earlier.

Reply to
Ian Field

I'm thinking; pretty decent reservoir between bridge rectifier & buck I/P.

Reply to
Ian Field

Sounds like you had a metal body "rubwheel" dynama if you were forced to make one or the other ground.

Reply to
Ian Field

Increasingly, motorcycles are built with field controlled alternators just like cars, but there's an awfull lot still in circulation with 3PH PM alternators, that's 3 shorting SCRs in the rectifier/regulator module.

Reply to
Ian Field

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Its obvious that you're using too many of your few remaining brain cells trying to think up insults to hurl at me, to read the thread and see what I actually did ask!

No the battery will not be the filter - its to be charged by the buck that load matches the alternatot O/P.

No its not running bulbs.

The LED lighting set I designed leaves some charge to spare as is - I want more for occasional use of a Cree LED from the same charging system.

Its difficult to respect your knowlege & experience when you use it to be plain nasty.

Reply to
Ian Field

That won't necessarily stabilize it; it might be unstable all the way down to DC.

John

Reply to
John Larkin

Right. All his energy is going into criticism, with none left to think about what's going on here, much less to try to help.

It's actually an interesting problem, to design a battery-charging regulator that optimizes power out from an alternator. AND is stable! Obviously, a uP would do it, but there is probably a simpler analog thing that would work pretty well, some unusual regulator feedback topology. Jim could figure it out if he let himself, but he has a different agenda.

Exactly.

John

Reply to
John Larkin

It was 18V with no load at the output of the rectifier; that would make the input about 7V RMS.

The charge current into a SLA battery that results, is suitable for charging while the headlamp is off, and for running the headlamp and slow-charging the battery while cruising in the dark.

It was my thought that the metal core of the windings was not suitable for higher frequency excitation (the eddy currents in the metal were shunting the output windings, effectively). Rotating resistance was high even with no electrical load.

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whit3rd

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Electricity is frighteningly cheap compared to muscles.

Reply to
Ralph Barone

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Me too, about 15 years later... My comment about 100 W comes from pedaling the damn thing while my partner attempted to debug the electronics and determine optimum timing of the switching sequences.

Reply to
Ralph Barone

Nonsense. Read what I said. Larkin said rectify. I simply pointed out it's already done.

Crap!

It _is_ an interesting problem, but the negative resistance issue has me puzzled.

I know.

I didn't. Get that chip off your shoulder and learn to read.

You too, John. You must be losing weight considering all the shit you keep dumping :-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

That's the puzzle... how do you model the problem. It's a current generator, yet inductively limited... how do model that into a source impedance?

And what happens when you add rectifiers? ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

You must have had a shorted diode in the rectifier block!

Off load most bicycle dynamos can give quite a belt when turned at a decent rate.

IIRC; the "rubwheel" bottle shaped dynamos were the worst, and I totally remember measuring a bit over 200VAC from an unloaded SA hub dynamo.

Same goes for motorcycle PM alternators - although they can deliver a fair bit more current before the voltage gets dragged down below the lethal threshold.

Reply to
Ian Field

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Some of us used a variable speed DC motor for bicycle testing purposes ;-)

But, in testing a tread-mill, I wanted to test transient loading and jumped on it and got thrown on my ass... drawing another cheering session from the technicians :-( ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

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"Energy: Their peak output was 12 kilowatts per hour, enough to run four kettles."

Trust journalists to always get the units wrong.

John

Reply to
John Larkin

Then stop flailing and think about it.

Nothing to say on-topic, as usual.

John

Reply to
John Larkin

It's only approximately constant-current if you graph nearly-shorted load current as a function of shaft speed. At any fixed speed, it's obviously a voltage source behind some inductance and resistance. That internal source voltage and frequency both go up proportional to speed, which combined with the inductance is why it tends to be constant-current into a lo-z load *against*speed*.

The model is simple: sinewave voltage source whose amplitude and voltage track; inductor; resistor. Experiment to find the values.

Conservation of Energy and the Maximum Power Transfer Theorem suggest that maximum torque happens with some non-open, non-shorted load.

If the load is low impedance, the rectifiers don't matter.

Now, design a switching regulator to take the output of a varying-speed PM alternator and optimize battery charging.

John

Reply to
John Larkin

Get over it John. I've figured out how to model it. Now, if Ian will take some load/speed data I can fit the coefficients. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

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