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Smart Drives Senior Member Joined: 06/07/2009 Location: AustraliaPosts: 115
Posted: 12:03am 19 Jul 2009
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Hi everyone,
I am about to connect 3 x 24 volt wind turbines to my battery bank. I have 3 x 25mm2 cables. I am hoping(praying) that i can take the 1st phase of each turbine to wire 1, second phase from each turbine to wire 2 and third phase to wire 3. Then split wire 1 back to 3 wires at the rectifier then connect to the batteries
and so on for the other two wires. will this work ?
Thanks.
Cameron.
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JackS Newbie Joined: 04/03/2009 Location: New ZealandPosts: 7
Posted: 07:41am 19 Jul 2009
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If you are saying combine 3 seperate wild AC generator outputs from 3 separate wind generators as 3 phaze AC then I would say No as they will tend to fight each other as the speed/frequency/phaze would not match.
You may be able to rectify to DC then combine them depending on your regulator setup.
woodchips Newbie Joined: 05/01/2009 Location: United KingdomPosts: 27
Posted: 05:00pm 19 Jul 2009
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Hello
No.
Never connect AC things in parallel, the circulating currents will set it all on fire.
DC is better, but won't there be problems with the load continually changing on each windmill due to the bus voltage it is working against continually going up and down?
Bob
Robb Senior Member Joined: 01/08/2007 Location: AustraliaPosts: 221
Posted: 04:22am 20 Jul 2009
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3 rectifiers at the junction point then run DC down the cable. Waterproof all the DC side well.
Smart Drives Senior Member Joined: 06/07/2009 Location: AustraliaPosts: 115
Posted: 08:40am 20 Jul 2009
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Bugger, the problem is the cable is burried from an earlier turbine setup, and i am too far away to run DC at 24 Volts (will lose to much power). Is there a way to pump up the voltage in DC so i dont lose it all in transfer (that doesn't cost an arm and a leg ) ?
and then drop back to 24 Volts at the batteries.
Thanks.
Cameron.
All smart drive parts sold
Custom built turbine parts on
Multicam flatbed CNC Router
davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499
Posted: 10:07am 20 Jul 2009
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There is, but the loss for converting it up and then down again at the other end is going to hurt. Also, having high voltage DC running around the place is MUCH more dangerous then high voltage AC. In fact there are special regulations in this country regarding DC voltage above 32 or 48 Volts.
I got about 2 million hits on <3 phase to single phase converter>, see what you can find.
davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499
Posted: 10:36am 20 Jul 2009
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Well, I didn't find anything useful. Can the F&P be re-wired to produce single phase? Easily?
Hang on a moment, you say you have three wires. Can't you just rectify at the far end without the ground return. All the phase currents should be equal.
I don't have much 3 phase experience, so maybe someone can say why this is not a good idea. Edited by davef 2009-07-21
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 10:49am 20 Jul 2009
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1. As a last resort you can put the batteries and the inverter at the turbine/s (if near each other) and run the inverter from up there .... only need to transmit single phase 240v then.
2. Use three phase transformers to up voltage the mill then rectify to DC and transmit. (I could see 9 microwave transformers with a rewound primary if cost.. not time is the essence. The down shift could be psu supplies. This is a time not money exercise..... all should be free.
3. Rectify and DC:DC convert at both ends. Fast but expensive. (commercialised #2)
4. Wind the turbines for HV and rectify and transmit.... only DC:DC conversion at one end. (no transformers)
5. Bury more cable.
I'm figuring 1 or 5.
........oztulesVillage idiot...or... just another hack out of his depth
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 02:48pm 20 Jul 2009
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Here is a crazy? point 6. for you oztules:
Use a single 3 phase transformer with 3 separate primary windings and one 3 phase secondary winding. My three phase theory is too rusty by now to figure out if that would work so I pass this little challenge to you Klaus
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 08:44pm 20 Jul 2009
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Hi Carrying Ac at the higher frequencies generated by FP units is very lossy. I had a moment and did a test on my one of my hydro units, these unlike windmills have a constant input power and allow constructive testing nearly to the standard of bench testing.
First I ran the unit with a 30 metre 2.5mm 3 core cable added between the rectifiers and the windings. DC output to my batteries was 14 A.
Now I reconnected the rect directly to the windings as close as pos ( this is always my policy ) and used the same cable connected between the batteries and rect 2 cores in parallel +ve other core -ve simulating a 30 metre run to the batteries output is now 21 A No other changes.
Cameron Use rect on each turbine.You can only combine varible ac frequencies by rectifing first.
use rectifiers at each tubine then parallel the dc to two cores in parallel +ve other -ve. with existing cable.
re the theory on three phase yes it does mean you can run three single phase supplies on three wires in stead of 6 but the saving in the small distances we use is minimal.
re comment re 24 dc needing to be pumped up for distance runs yes great idea but no more than AC .
The work being done by the members on smps I see as heading this way. At least it is a area I want to use them. Transporting high voltage DC is the answer. In NZ / Aust we are allowed to go to 100V before regs kick in after that you only need a registered person to instal cable. Luckly I can do my own.
Even the main grids go back to DC for many reasons when the going gets tough. My initial training was in the commissioning of the DC link in New Zealand 600 MW 500Kv(250 to earth ) using huge mercury arc rectifiers.
Edited by herbnz 2009-07-22
Robb Senior Member Joined: 01/08/2007 Location: AustraliaPosts: 221
Posted: 12:46am 21 Jul 2009
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If they are smart drive mills can you rewire them for higher voltage?
Smart Drives Senior Member Joined: 06/07/2009 Location: AustraliaPosts: 115
Posted: 01:07am 21 Jul 2009
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Thanks for everyones input, i am using 2v 500amp batteries and i only have 12 . I am starting to think i might have to put these in to storage as i have heap of 300amp 2 volt batteries. This way i can jump to a 48 volt system but i will still have go back to 24v for my pure sine wave inverter (which cost me a $2,000 so i dont really want to toss that !) That will make my losses drop from 28% back to 8% which is acceptable.
Does anyone have a 48v to 24v converter that can handle 30amps(48v) or maybe i could use 3 10amp(48v)to 24v(20amps).
Once again thanks.
Cameron.
All smart drive parts sold
Custom built turbine parts on
Multicam flatbed CNC Router
Smart Drives Senior Member Joined: 06/07/2009 Location: AustraliaPosts: 115
Posted: 11:02am 21 Jul 2009
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Problem solved, Thanks to sPuDd i now have 48v inverters
so i am wiring up 3 100S units in star with a steppar to switch to Delta. 48v star wired in a 100S kick in at 200rpm . 300 watts at 400rpm at 500rpm i will change to delta (about 350 watts) then it will max out at 630 watts at 750rpm. best of all i dont have to dig another trench !
Thanks.
Cameron.
All smart drive parts sold
Custom built turbine parts on
Multicam flatbed CNC Router
woodchips Newbie Joined: 05/01/2009 Location: United KingdomPosts: 27
Posted: 07:17pm 21 Jul 2009
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Hello
Just how long are these cables? 25 sq mm is a pretty big cable, resistance is only about 1 ohm per km. Even at 100m 10A is only a 1V drop.
Bob
Smart Drives Senior Member Joined: 06/07/2009 Location: AustraliaPosts: 115
Posted: 11:04pm 21 Jul 2009
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Its 100m from the turbines to the battery bank (Due to large trees next to my house). I will get approx 13 amps
from each so 39 amps in total.
Thanks.
CameronAll smart drive parts sold
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Hi all,
Was interested to read what Herbnz said about the losses involved when running 3 phases over a long distance. I actually thought you would loose more converting at the windmill and running dc from windmill to battery bank. I am no electronics wizz and will take onboard the results of your experiments, will have to modify a couple of things. Thanks for your input...cheers Pete.
I have toyed with the idea of using 1/2 copper pipe as a buzbar, just unroll it to wherever you want to take heavy current to.
Yesterday I needed to repair my welder leads, so I cut a 4 inch length off, then insurted the ends of the welder leads (output leads) then hammered both ends flat, made a great fitt.
Saved buying the propper lugs from the expensieve shop which is too far away from me anyway.
jim
HeadsUp Regular Member Joined: 06/12/2009 Location: AustraliaPosts: 43
Posted: 06:53am 30 Dec 2009
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gee Jim i hope youre a licenced plumber , dont wanna get electrotickled .......... ;)
.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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