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Author Topic: AC DC 250v or 600v  (Read 3532 times)
camillitech
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« on: November 14, 2014, 09:37:05 AM »

Bit of a dilemma here chaps,

I need to move the electrickery from my Stream Engine hydro turbine 200m, or do I?

One of my hydro turbines is 450m away from the house I'm in just now, it generates 3 phase at the turbine and is transformed and rectified to charge my 48v bank. Anyway, current house is sold and I need to move the energy to the new house 200m away. The normal AC voltage at around 800w is 250 and the OC voltage around 450.

I seem to have several options, extend the DC from the transformer straight to new battery, would need 35mm square 2 core at least.

Extend the three core 200m to the new battery bank and put the transformer there, 4mm or 6mm would do.

Rectify it where it is now and 'AC couple' it for the price of an inverter with no cables required. This would seem the cheapest and sensible option but the OC voltage once rectified would, I'm guessing be close to the 600v limit of most small inverters.

Any one know of an inverter that will take more, or a way of clamping the voltage at 600v.

Any suggestions of other alternatives most welcome.

Cheers, Paul
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Fintray
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« Reply #1 on: November 14, 2014, 10:28:20 AM »

Put the AC through a 240 to 110 transformer, rectify it and put into inverter?
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billi
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« Reply #2 on: November 14, 2014, 10:29:09 AM »

Hi Paul ,

if its transformed to 48 Volt DC  you could  use a small  GTI  like a Soladin or bigger ?

Not the most efficient  way , i assume


But , this sounds ok to me
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Extend the three core 200m to the new battery bank and put the transformer there, 4mm or 6mm would do


Billi
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camillitech
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« Reply #3 on: November 14, 2014, 12:50:03 PM »

Put the AC through a 240 to 110 transformer, rectify it and put into inverter?

It's three phase Fintray, would that work?

Extend the three core 200m to the new battery bank and put the transformer there, 4mm or 6mm would do



That's the way I was leaning Billi, for two reasons, 1, I know it'll work and 2 it's going straight into the batteries. However it does mean buying 200m of SWA and laying it. Whereas if I 'AC couple' it I could probably get a second hand GTI for buttons, I actually have a new SB3800 which is good for 500v and I've just noticed it will disconnect if the voltage gets too high. As my 'mini grid' is already in the shed where the transformer is, I could in theory be 'up and running' for the price of a rectifrier. On the other hand I could end up  sh*tfan

Cheers, Paul
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« Reply #4 on: November 14, 2014, 03:34:19 PM »

Duh, sorry missed the 3 phase bit!

Why not rectify it at the turbine then only 2 core SWA required?
TLC show 4mm 2 core SWA at 125/100m, might be worth trying your "nearest" electrical wholesaler for a better price.
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guydewdney
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« Reply #5 on: November 14, 2014, 05:01:42 PM »

The "wind interface" of a power one system limits voltage to 530v......
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Tinbum
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« Reply #6 on: November 14, 2014, 05:37:03 PM »

Duh, sorry missed the 3 phase bit!

Why not rectify it at the turbine then only 2 core SWA required?
TLC show 4mm 2 core SWA at 125/100m, might be worth trying your "nearest" electrical wholesaler for a better price.

Also volt for volt dc transmission is also more efficient.
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« Reply #7 on: November 14, 2014, 06:56:39 PM »

Over distance AC high voltage wins out, as you say one can use thinner cables.

If it were me I would send the 3 phase AC all the way, then you can see what the cable length voltage drop would be, then into some rectifiers to DC. That new Tristar Battery Charger unit can take 500vdc. ?

On the other hand Second hand SMA Sunny Boys are a good price and you can AC couple after your rectifiers now its DC voltage, into your mini Grid at your shed.
NB, I notice that my SB1200 will take 400vdc max while the SB3800 will take 500vdc max. 

I did get some 4 core 16mm/2 for my trackers 130meters distance on the DC output, from fleebay at a good price, and doubled up the cores so I have 32mm/2.

NB, according to Hugh when AC is rectified the DC voltage is nearly 40% more,  faint hmm not sure of that, need to look at that a bit more.
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« Reply #8 on: November 14, 2014, 07:08:50 PM »

I'm with Clockman, you don't want your kit out in the pi$$ing rain, AC all the way, if it means smaller cable.

keep your rectumfrier warm and dry  ralph
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camillitech
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« Reply #9 on: November 14, 2014, 07:52:13 PM »



NB, according to Hugh when AC is rectified the DC voltage is nearly 40% more,  faint hmm not sure of that, need to look at that a bit more.

Methinks you multiply the AC x 1.412 to get  the DC CM.

Why not rectify it at the turbine then only 2 core SWA required?

It's already 3core and three phase for 450m to the shed from the turbine, so no point altering that. However rectifying it in the shed then sending the high voltage DC down twin core to the new house is worth investigation.

The "wind interface" of a power one system limits voltage to 530v......


So basically it just 'trips' and does no harm? This would be the simplest solution as there is already a 10 or 16mm square mains cable laid between the shed and new house. Hmmmmmmmmmm
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guydewdney
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« Reply #10 on: November 14, 2014, 07:57:44 PM »

It gradually cuts in a dump load maintaining the 530v. Pretty crude but works.
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« Reply #11 on: November 14, 2014, 08:03:57 PM »

The "wind interface" of a power one system limits voltage to 530v......
 

Good thinking  GuY

Was there not as well  a WindyGirl idea ?   http://www.windygirl.biz/    

Paul ,    i hope you keep   a  part of   battery charging on the DC side  as well
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camillitech
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« Reply #12 on: November 14, 2014, 08:08:55 PM »

It gradually cuts in a dump load maintaining the 530v. Pretty crude but works.

Ahhhh, I recall you mentioning this in a post some years ago, think you referred to it as a 'bit of a sledgehammer' or words to that effect, crude but effective. Sounds like the way forward for me really, the voltage from the turbine is only ever likely to exceed that if the GTI 'drops out' for some reason. However, as I type this I realize that this does occasionally happen with the SMA GTI's if I start my large 'chop saw'. Hmmmmmmmmmmm  help 
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« Reply #13 on: November 14, 2014, 08:13:40 PM »

Paul.......

I am getting worried about the Sunny Island charging regime.

Like you, I think, ? I will retain DC battery charging with my 3 tristars, my Midnite and Morningstar MPPT controllers.

My main concern is that the Sun is out, I am getting PV feed in to the SI Mini Grid, AC Coupling, and my Tristar battery charger controllers go to Float first and the ruddy SI keeps trying to put a charge into the batteries.

Then my 3 tristar controllers then try and dump excess voltage, into my 8kW of dump loads,,,,, aaaaaaggggghhhh.

I will experiment.  
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guydewdney
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« Reply #14 on: November 14, 2014, 08:19:08 PM »

I have a spare interface, but sonething went wrong with it. Will try to find out. If it still works as an overvoltage protection (a 500v zener diode?) then you can have it.
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