John Lussmyer via EV wrote:
Would a "bad boy" full wave 3 phase rectifier work? (I'd probably need to
adjust the voltage output of the generator.)
Figuring out the inductor size might be a bit difficult, but hopefully not TOO
critical.
I'm unlikely to need more than about 30KW out of this continuously.
It's not critical. The more the better (up to the point where the
inductor becomes impractically big/heavy/expensive, or its resistance
adds too much loss/heat).
The inductor's job is to spread out the current spikes at each AC peak.
32kw at 320vdc is 100 amps average. With no inductance, the current is
liable to be 400a spikes for 1/4 of the time. That will put a real
strain on the diodes and wiring.
The more inductance you add, the smoother the current becomes. The peaks
go down, and fill in the zero-current valleys.
If you manage to get too much inductance (which would probably take an
inductor too big to lift), the output current essentially becomes DC.
The current in each of the 3-phase windings becomes a 33% on-time square
wave.
Note: That big inductor will have a hell of an inductive "kick" if
something tries to interrupt the DC output current. A switch, fuse, or
circuit breaker on the DC output will arc like mad if it opens while
charging at 100A!
An old arc welder transformer should work as an inductor. Disconnect or
remove the primary and rectifier, and use the high-current secondary as
your inductor.
If you want to fully regulate the output voltage and current, three of
the diodes in the bridge could be replaced with SCRs, and phase
controlled. Copy a classic circuit from an SCR manual, or use your
favorite microcontroller and program it yourself.
And also thanks for giving the ONLY useful answer that didn't boil down to "go buy a
30KW 3 phase hi-voltage charger".
You are most welcome! Though my solutions are often on the crude / old
tech side, that is because it's more likely that people can actually
*do* them. Wonderful high-tech solutions are great on paper; but often
never get implememted.
In your case, I know you are a great programmer; so a solution that
includes a micro is not going to be a roadblock. That's the part you
like! :-)
--
You never change things by fighting the existing reality. To change
something, build a new model that makes the existing model obsolete.
-- R. Buckminster Fuller
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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