Matching to the impedance of an alternator.

Aha! I thought that, but wasn't sure. That certainly makes it easier to derive parameters for a behavioral model.

Thanks again, Marcel! ...Jim Thompson

Thanks, Marcel!

You've been married to one woman since you were an undergraduate. How many models have you mounted in the interim?

And where is the switcher design you promised to post yesterday?

John

None. But you walked into that >:-}

Milking the Schadenfreude for all the joy I can attain first ;-)

Maybe I'll drive you truly wacko and provide a custom chip design at device level :-) ...Jim Thompson

Sounds like a very, very limited "social" life to me.

You seem to enjoy Autoschadenfreude, making a fool of yourself in public. And you're good at it.

When?

John

Very many thanks.

Even though the SA type I'm after isn't filled in yet, there should be more than enough data there to help me make an educated guess.

Naaaaah! Clearly you're "the man"-ic depressive, self-fool-making master on this group ;-)

Actually I think I'll do it with a 555 and irritate you and Slowman at the same time :-) ...Jim Thompson

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ad

using

=A0 =A0(Richard Feynman)

I haven't tested the Sturmey-Archer. Got a Shimano recently, though, and was amazed at how "peaky" (extreme odd order harmonics) the waveform was. This occurred for open-circuit and at rated load over a fairly representative range of rpms. So at least for that unit, the simple-minded calculations are substantially off {though they may be a fair starting place if you're iterating to a solution}.

Well, do *something*.

JF can help you if you decide to undertake a 555 design.

John

AHA!

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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and

Yes, really. See below.

Look at the data Marcel posted. The flat part of the current-versus-speed curve is where Xl is greater than R.

If Xl >> R, Q is high. And the coil will be driven above rated current by the factor Q. And the heating goes up as I^2.

Look at Marcel's data. Real measured numbers.

Why would anyone waste 10x the necessary amount of expensive copper because somebody might use the alternator in an unconventional way?

I suggested one way to double the load current: a 2:1 step-down autotransformer. You need a schematic for that?

John

Simple. Run it at a speed where Xl is four times the copper resistance, somewhere out towards the right end of the graph Marcel provided. Now connect it to a capacitor that series resonates with Xl. The current will increase to about 4 times the short-circuit current. The copper loss will be 16 times normal operation. That should warm things up.

But hey, don't stop whining on my account.

John

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and

You want me to show you the schematic of a 3-wire autotransformer?

It's amazing how much some people can forget in 50 years.

John

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load and

Well! You could prove that it works, though I know that it does, since I reported that I checked it out with the Hub Dynamo model fit to Marcel's data. But it lacks regulation, though I do opine, that the battery plus two bulbs as load may obviate the need for any regulation. ...Jim Thompson

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inductance,

One of the things about being an engineer, and not a a scientist, is that we don't have to prove things, we just have to make them work. If a rough scribble or in-your-head calculation shows that something is or isn't an issue by some large factor, that's all you need to know.

I don't have to run Spice to know that a small step-down transformer will increase the current output of a hub generator, once the speed gets into the constant-current regime.

John

I'm an engineer, so I don't have to show a schematic with values ?:-)

I only ran it because I was skeptical of the flatness of the regulation... turns out they blow a hellacious amount in iron losses. ...Jim Thompson

Have to? Depends on who is paying you to do what.

Circuit topology ideas can be played with, without parts values. We do that on whiteboards all the time. Architects can present renderings of their designs without specifying how many yards of concrete will be needed.

John