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Old 17th December 2012, 06:24 AM   #11
RJM1 is offline RJM1  United States
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And then there is the voltage conversion the cycloconverter will not do. You would still need a transformer to drop your voltage from 500Vac to 125Vac. A 3000VA 500V transformer might be hard to find.

Last edited by RJM1; 17th December 2012 at 06:37 AM.
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Old 17th December 2012, 11:47 PM   #12
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RJM1
480-500VAC 3phase is a fairly common configuration on maritime/aviation vessels and configuring a delta set of transformers seems not to be as challenging as dealing with the Hz. Those parts are fairly easy and cheap via salvage but setting up a working diode array has a lot more going on.

freax
Let me understand how you would approach this, are you suggesting that I aggregate the entire turbine output to DC and invert to the specified AC from there? This would seem to require triple the part count with quality/protection circuits and because of the high power levels we are working with could become unaffordable really fast. Synchronizing and balancing the wave cycles isn't looking like too much fun either if that were indeed an issue.
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Old 20th December 2012, 08:12 AM   #13
freax is offline freax  Australia
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Quote:
Originally Posted by gmaslin View Post
RJM1
480-500VAC 3phase is a fairly common configuration on maritime/aviation vessels and configuring a delta set of transformers seems not to be as challenging as dealing with the Hz. Those parts are fairly easy and cheap via salvage but setting up a working diode array has a lot more going on.
Is it 3 phase?
Also transformers have a fair amount of power loss.

Quote:
freax
Let me understand how you would approach this, are you suggesting that I aggregate the entire turbine output to DC and invert to the specified AC from there? This would seem to require triple the part count with quality/protection circuits and because of the high power levels we are working with could become unaffordable really fast. Synchronizing and balancing the wave cycles isn't looking like too much fun either if that were indeed an issue.
On second thoughts considering that its 500vAC I'm not sure that you should even try, that would bring the Voltage up by quite a margin and into and past the kilovolt range.

What you could do is use a custom wound transformer with a 500vAC primary and a couple of low voltage high amperage secondaries, then rectify that, filter it, then dump it into an inverter, there is your 115vAC at 60Hz.

Or If its unfeasible to convert it to DC then consider finding one of these: Motor-generator - Wikipedia, the free encyclopedia

This would in my book be the safest route to take, finding one of those shouldn't be too difficult.

Aside from that ask someone else because I've come up empty handed, you are asking a fairly difficult question, you want the 500vAC output of a generator to come down not only in frequency but in voltage in one step with high efficiency, which is going to take some considerable power loss to do no matter how you cut it.

You know what I would do? sell the generator to someone else who can put it to good use and go out and buy a proper 125vAC single phase generator.

Either that or get the generator head rewound.
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Last edited by freax; 20th December 2012 at 08:35 AM.
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Old 22nd December 2012, 01:31 AM   #14
JMFahey is offline JMFahey  Argentina
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Funny, never heard of 1KHz generator.
Can you link to some place which shows one?
What will drive it?
Gasoline/gas/wind/water/fusion/fission?
Do you need the 3 phases ?
Straightest solution I see is rectifying those 500VAC , being 3 phase you will have very low ripple to begin with, being 1KHz makes it even easier, and *then* invert it, so you solve 2 problems in a single step.
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Old 22nd December 2012, 01:54 AM   #15
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There is likely no way to re-wire the generator stator for 60Hz because of insufficient back iron between so much greater a grouping of poles. (except for impractical reduction in power output and efficiency) Even the rotor is probably mutli-pole. You'd be faced with some kind of rectification and inverting plan.

Last edited by Andrew Eckhardt; 22nd December 2012 at 01:57 AM.
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Old 22nd December 2012, 02:03 AM   #16
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Default or really old school...

Although I never saw it, here is what the U.S. Government did until the 1980s: imagine you have a building full of "american" electronic equipment (120 VAC, 60 Hz) but you are in a European country (220 VAC, 50 Hz). We used something called a "rotary converter" which apparently was little more than a very large 220 V motor connected to a 120 V alternator! They had a diesel generator hooked in by some means for emergency back-up but it was not highly reliable. But anyway there is a "West Virginia" solution for those who, like the government, have lots of money and little common sense!
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Old 22nd December 2012, 02:07 AM   #17
DUG is offline DUG  Canada
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Greetings gmaslin.

Another technical quest.

What about an MG set...how efficient are they?

I have no idea but it might be better than translating to and from DC.
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Old 22nd December 2012, 01:06 PM   #18
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DUG
I'm still working the numbers here so I don't have your answer.

Andrew Eckhardt
Absolutely corrent.

Soldermizer
That's a funny anecdote that just might become useful.

JMFahey
It's an oddball prototype gas turbine. Really quiet, smooth and strong. I think freax suggested this too and it looks like going DC first might be the least problematic all things considered.

freax
Your voltage comments with DC conversion are noted and I thank you for your well considered replies.

DF96
I think rectifying first and inverting to spec is looking like the smartest solution so thanks for hinting me there.

Last edited by gmaslin; 22nd December 2012 at 01:16 PM.
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Old 22nd December 2012, 01:54 PM   #19
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Are you seriously suggesting the Toshiba M-G Set pictured here for me? I thought you were talking about a set of diodes, LOL.
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Old 23rd December 2012, 12:18 AM   #20
JMFahey is offline JMFahey  Argentina
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Motor generators are an old school classic and can be purchased for pennies at military surplus shops (the ones which are 1 acre size with a 2 story high mountain of military junk, including rusty tank engines and Vietnam era radio packs with bullet holes, no kidding).
Problem is they usually convert 50 to 60Hz and vice versa, or AC to *a lot* of DC .
And you would require one driven by a 1000 Hz motor .
So the real solution is going DC (which solves the frequency problem) and invert.
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