# Transforming the output of a Wind Turbine Generator

#### vielle568

Joined Feb 3, 2012
13
I have installed a wind turbine on my property. It has a 3KW generator that outputs 240V to charge a bank of 20 x 12V batteries connected in series.
There are two problems with this set-up:

1) When one of the batteries in the bank fails the whole system comes to a standstill
2) The inverter has recently failed and I cant get a replacement

What I would like to do is to reconfigure the system at 12V by connecting the batteries in parallel. My question is how do I transform the voltage coming out of the turbine generator down to say 14V to charge the bank of batteries?

There are three wires (and ground) coming from the generator, so do I need three unity transformers connected in parallel to obtain a single phase 240VAC output? Perhaps then a regular charger can be connected to charge the batteries?

Im only guessing; please put me on the right track! Thanks for any suggestions.

Vielle568

#### DMahalko

Joined Oct 5, 2008
182
You would need to post model numbers of the equipment and probably a schematic of how the existing system is wired, for this discussion to go anywhere.

Does the generator directly charge the battery bank, or is there an intermediary charger/inverter device between the generator and the batteries? The inverter may be a dual purpose charge controller too, or the generator could have such capability by itself. Unknown.

If a battery fails and the whole system goes down, that suggests the charge controller is doing its job, sensing the voltage is too low and not charging the string.

Wiring them in parallel will not do you any good if a battery fails. All the others will discharge through it uncontrolled, and this will possibly boil the bad battery's electrolyte or blow it up, plus also damage all the other cells due to being in a continuous discharge state.

You really should have a controller in there to mediate these failed-battery interactions before they get out of hand.

But it's too hard to make any educated guesses without a schematic.

Lead-acid cells are about 2.3 volts each when charged, so a string of 20 12v batteries is actually about 276v. (Hmm, another "odd" alignment of DC with AC, 277v RMS...)

#### vielle568

Joined Feb 3, 2012
13
Thanks for your comments about my project. I've attached a basic system diagram showing the set-up. Sorry, but I have no more technical information than this to offer.

There is a charge controller that functions correctly. The problem with the system is the inverter that has stopped working. I've asked the manufacturers for a schemantic but they tell me that their design is confidential and they will not release any information. The unit was constructed and shipped from China and so you can probably understand the difficulty in follow up and after sales service; it simply doesn't exist.

I was hoping to reconfigure the wind turbine system to 12 volts in order to replace the inverter with a model that I can buy over here in the west. I have inspected the existing inverter but have found no evidence of a burnt component or fuse. Normally the inverter would go through a brief start-up cycle before a green LED would indicate power, but now there is little sign of life. I don't know if the H-bridge transistors are damaged or if the electronics that control the inverter are causing the problem; there are some PICs here and without a schematic this is too complex for me.

I've included a couple of photos of the inverter (both sides without the covers); the H-bridge is up at the top on the right on the first phot with the huge transformer down at the bottom.

Any suggestion or ideas onhow to get this system back into operation would be greatly appreciated. Thank you.

Vielle568

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#### DMahalko

Joined Oct 5, 2008
182
You should still be able to find a new inverter that will work with your system.

This is NOT what you want since the output is 60Hz for USA, but just an example that your 240v DC system is not in any way obsolete.

SMA Sunny Boy 3000US Grid-Tie Inverter
http://www.sma-america.com/en_US/products/wind-power-inverters/windy-boy-3000-us.html

Input (DC)
Max. DC power 3200 W
Max. DC voltage 500 V
DC nominal voltage 250 V
Min. open circuit voltage for activating "Turbine Mode" 228 V
Operating range "Turbine Mode" 180 V – 500 V / 200 V – 500 V
Max. input current 17 A

The main item to note here is that this device isn't specific to 240v DC, but actually a wide range of DC voltage input, so finding a device intended for "exactly" 240v DC isn't required or necessary.

Also it's unclear to me if you want grid-tie capability or just a standalone inverter for your own off-grid needs.

I see that SMA has a website for France, which will likely have the specific inverter models you need. I do not read or speak french, but this looks like the same unit for 50Hz 230v AC output:

http://www.sma-france.com/fr/produits/onduleurs-pour-energie-eolienne/windy-boy-2500-3000.html

You really need to get assistance from a qualified local electrician specializing in off-grid power systems. This SMA company may have some recommedations for you if you need help.

#### DMahalko

Joined Oct 5, 2008
182
Also a good question to ask, is how long you've had the system installed, and how often you have a battery failure.

If you are having very frequent battery failures, you may be using the wrong type of battery for the application, such as using automotive starter batteries rather than deep-cycle batteries.

If you are discharging them too deeply for too long, then you need batteries with either more reserve capacity or a more durable plate design.

#### DMahalko

Joined Oct 5, 2008
182
This looks like the Kingship generator, company product info:

Well, finding a replacement inverter at their price will be hard. the SMA one I found is something like $2300, but this Kingship 3KW inverter is ...$350?

Page 14:
FD4.0-3000 3KW WIND GENERATOR SEPARATE PRICE (Intelligent Type)
No. - Designation - Quantity - Unit price (USD)
1 - Turbine - 1 set - $1900 2 - Blade - 1 unit (3Pcs) -$90*3
3 - Controller - 1 set - $360 4 - Inverter - 1 set -$350
5 - Tower - 1 unit - $420 6 - Storage battery - 20Pcs(12V 120AH) -$60*20

You may be better off seeing if they have a replacement inverter for their own system. That may be the lowest-cost replacement option.

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One more thing to ponder before plonking down your hard earned $$on a new unit from the same company.. We've got a 6kW PV system on our roof with a pair of German inverters -- they are failing at a rate of about 1 failure every 2 years which is then repaired under warranty (warranty runs for about 10 years)... IF yours has failed within a few years of being installed, it's possible that the new one might follow suit and do the same -- costing you$$ every few years. If that's the case it might be better to buy a decent product such as the above mentioned SMA Sunny Boy inverters which I've heard tons of good stuff about... Anyway, just something to ponder -- weigh in all angles of the equation..