Fluorescents and migraines??

In alt.engineering.electrical Jeff Jonas wrote: |>|> Or maybe we just need DC distributed in the home. But don't get any idea |>|> that Edison was right ... he was selling pulsing DC. | |>| That's interesting. What do you mean by "pulsing DC" --- unregulated? The |>| Smithsonian historical material indicates that the steam-powered generators |>| were speed regulated and the load was just incandescent lamps initially, of |>| course. | |>Edison's generators output DC by reversing the electrical connections every |>half cycle. The end result is basically the same as a full wave rectifier |>bridge. You get 2 pulses per cycle. I don't know what speed his generators |>actually ran at. | | Edison's generators were rather clever: they had a bus bar equilizer | so each shared the load equally (varied the field coil?). | If the generators were intentionally out of phase, | that would smooth out the combined output.

2 or 3 alternators on the same rotor shaft, aligned at different angles, could do that phase shift, I suppose.

Interesting concept ... 3 phase DC. I've seen circuits for AC to DC power supplies that were designed to use 3 phase AC power to get smoother DC by means of 3 full-wave bridges. I never worked out what kind of current each of the 3 AC phase lines would have. The one I first saw was wired delta.

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phil-news-nospam
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Why stop at three? There are already DC/DC converters that use six "phases". The trade off is between circuit complexity and smoothing capacitors required. With IC components the former is trivial.

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VWWall

In alt.engineering.electrical VWWall wrote: | snipped-for-privacy@ipal.net wrote: | |> Interesting concept ... 3 phase DC. I've seen circuits for AC to DC power |> supplies that were designed to use 3 phase AC power to get smoother DC by |> means of 3 full-wave bridges. I never worked out what kind of current each |> of the 3 AC phase lines would have. The one I first saw was wired delta. | | Why stop at three? There are already DC/DC converters that use six | "phases". The trade off is between circuit complexity and smoothing | capacitors required. With IC components the former is trivial.

If by "six" you mean also to include the 180 degree opposing phases, that would be what I include in "three" phases (six pulse). The result would be a 300 or 360 Hz ripple for the capacitors to handle. If you get three phase power in, that is perhaps the simple setup. But you could also get a true six phases (twelve pulse) by having separate secondary windings on the

3 core transformer where 1 set are used for three of the phases, and another set or two are used in pairs from separate cores to get cross phase angles. You could also do this with a lot of separate transformers, but doing it with just 3 cores seems the most economical. Then the ripple would be 600 or 720 Hz and the capacitors could be even smaller.
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phil-news-nospam

Interesting topic.

I myself can't see flicker, nor do fluourescents bother me unless they buzz.

But my chronograph will not work with fluorescent light, and does work with incandescent. (very irritating)

I don't know the circuit involved. The chronograph calculates the speed of a projectile by measuring the time between screens. You need overhead light at both sensors.

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TimR

12 pulse converters are used routinely in variable frequency drives.
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Ben Miller

In alt.engineering.electrical Ben Miller wrote: | snipped-for-privacy@ipal.net wrote: |> In alt.engineering.electrical VWWall wrote: |>> snipped-for-privacy@ipal.net wrote: |>>

|>>> Interesting concept ... 3 phase DC. I've seen circuits for AC to |>>> DC power supplies that were designed to use 3 phase AC power to get |>>> smoother DC by means of 3 full-wave bridges. I never worked out |>>> what kind of current each of the 3 AC phase lines would have. The |>>> one I first saw was wired delta. |>>

|>> Why stop at three? There are already DC/DC converters that use six |>> "phases". The trade off is between circuit complexity and smoothing |>> capacitors required. With IC components the former is trivial. |>

|> If by "six" you mean also to include the 180 degree opposing phases, |> that would be what I include in "three" phases (six pulse). The |> result would be a 300 or 360 Hz ripple for the capacitors to handle. |> If you get three phase power in, that is perhaps the simple setup. |> But you could also get a true six phases (twelve pulse) by having |> separate secondary windings on the 3 core transformer where 1 set are |> used for three of the phases, and another set or two are used in |> pairs from separate cores to get cross phase angles. You could also |> do this with a lot of separate transformers, but doing it with just 3 |> cores seems the most economical. Then the ripple would be 600 or 720 |> Hz and the capacitors could be even smaller. |>

| | 12 pulse converters are used routinely in variable frequency drives.

Right. But is it worth doing 12 pulse AC to DC conversion? Is the cost of the extra transformer windings less than the savings in capacitors for typical ripple reduction requirements?

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phil-news-nospam

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