220V turbine to 48V battery store...

[(unknown)]

 I'm about to build a house on Crete in Greece & will be incorperating stand alone power via Solar PV & Wind power...

 PV side of things I have arranged, It will be 500W (expandable)& 48v nom & feeding a 48V battrey bank, over a relativly short distance ...

 The 2kw turbine I have in mind is avalible in 48 or 220V... 48v seems like the way to go to match the rest of the system... but with the distance from the rest of the system I'm going to loose a lot of power unless I run massive CSA cable. It's not so clever to move the battery store to the bottom of the tower as that impacts on the PV supply...

 I'm sure I'm not the only person with a mixed input system who finds themselves in this situation...

 I had considered running the 220V mill as the higher voltage would cut out a lot of the high current losses & then feeding into a 2kw 48V controler & switching in a 3 phase transformer when voltage hit say 70V but this is ineligant...

 Is there a piece of equipment out there that will allow me to feed my 0-220V unregulated 3 phase output into a 48V (nom) battery bank... I had thought an industrial DC motor drive might have the capability, but I'm just not smart enough to know...

 Thanks for reading my ramblings...

 Steve

 (Wales, UK)

[wpowokal]

Yes, but please post the distance your mill is proposed to be from the batteries so you may receive an intelegent answer.

allan down under

[(unknown)]

 Yes I can see that might help... Sorry Allan.

 Not that great a distance probably to start with 200 meters... but I do have my eye on a much higher site with a better aspect about 800-900m away... Need to do some negotiating with my neigbours though...

[Ungrounded Lightning Rod]

I don't see why you'd need to switch in the transformer.  With it in circuit all the time you're essentially in the same boat as if you had the 48V genny with wire about 7 or 8 gauges thicker (except for transformer losses.)

[Flux]

Not enough information on the turbine to help much. I assume this is some chinese copy of a Bergey or something.

How it will react to line resistance is something we have no idea of. At 48v you can go a fair way before line drop becomes a serious issue but for very long runs you may have to use the 220v unit. You will need a 3 phase transformer or 3 single phase ones and you will need to rectify the transformer secondary to charge the battery.It will behave similarly to the 48v unit as long as you choose the transformer to suit the operating frequency ( you would need to find that out). Start up may be slightly delayed but if you choose the transformer right it should be possible to start without switching the transformer out.

The transformers may not be significantly cheaper than the heavier cable for 48v, much depends on the turbine. If it is cheap and cheerful then it may object to much line resistance but in some cases a bit of added drop will increase the prop output and you may not see any loss until you go fairly silly with line drop.

There is no commercially available device that I know of that will take the raw ac and match it to the battery and maintain correct tracking of the prop power curve. You will just have the equivalent of the 48v unit but with less line loss but with the transformer loss added. That loss will be cost dependent, efficient transformers come at a price as they use more copper and iron and if the alternator frequency is below 50Hz at full load then you take another hit in terms of cost.

Bear in mind that the nominal transformer voltage will not be 220 unless full turbine frequency is 50/60 Hz. if it was only 30Hz then you would need a 440v primary standard unit and its VA rating would be halved.

Flux

[(unknown)]

 I had a chat with sombody who had tried using 3 single phase transformers to drop the output voltage of his mill... He was using a 48V to charge a 12V pack, he couldn't get it to start to turn unless it was blowing a gail... It worked OK once on the move, but from stationary the primary winding of the transformer acts like a short across the genorator winding... Hence needing to start without the transformer...

 It's an AC curcuit when on the move but acts like DC before it gets going...

[TomW]

Might try some motor run caps in series with the transformer primary winding [turbine side]. Caps block the  DC component at startup but pass the AC once it gets turning.

Just an idea.

TomW

[(unknown)]

 

 I thought the best approach to this situation would be to rectify the 3 phase out of the genorater & play with getting that DC to stay at 48-56V by choping it into a higher frequancy inverter transformer... thats why I asked if anybody knew about industrial DC motor controlers , as thats the same sort of proccess .

 A DC motor controler would be taking a fixed rectified AC input & turning it into a variable time sliced & smouthed DC output...

 I want to take a variable rectified AC input & turn it into a fixed time sliced & smouthed DC output...

 Shouldn't be too difficult, as the feed back control is still running in the same direction in both examples...

 If I were going on grid I would just plug straight into a grid tie inverter... maybe I could run with a higher voltage battery bank, but I think 48V DC is safer...

 I just thought sombody might have bumped into the "Low voltage at a High Current, over a longish distance" problem before & found an elegant solution...

 Thanks for taking time to reply to me guys...

 

[Flux]

It won't start into transformers if they are chosen for the wrong frequency as the magnetising current becomes excessive.

Yes the pwm controller will work but you will have to build it until such times as a commercial unit becomes available. You may be able to use an inverter drive as some sort of starting point but I suspect starting from scratch might get you there quicker.

If you are an electronics designer then go for it. Unless you include some form of cube law tracking it will just be the dc equivalent of the transformers.Having gone that far you might as well go the whole way if the efficiency of the turbine is high enough to justify it. ( I doubt that it will be unless intended for some form of grid tie inverter by the makers as the low efficiency will be needed to work as a direct battery charger).

Flux

[oztules]

" I just thought sombody might have bumped into the "Low voltage at a High Current, over a longish distance" problem before & found an elegant solution..."

Well here is 1 solution

 A 240v AWP turbine (about 11' diam)

A three phase transformer: Note the input voltage. (as per Flux statements elsewhere in this thread...)

Gadget to turn on transformers when approaching 20-25hz.

Then off to the batteries via rectifier . Simple and elegant.

This system is in a good wind site and delivers over 24kwh/day  a lot of ...2/3 of days, and very rarely less than 15kwh/day.

power inversion (sine output)and battery control is here, with dump controller alongside.

Am currently wrestling with 3ph dc motor drive....#@#@#@# things....... wouldn't use it for this application.

........oztules

[dinges]

Nice orderly setup, Oztules. Joy to look at.

Some questions:

• I assume you switch the input (primary) of the transformer? So it basically free-wheels until 20-25 Hz when the AWP starts to be connected to the transformer ?
  
• what ouput voltage does it normally put out ? I.e. 400V 50Hz input, xxx V output?
  
• what system voltage do you use ?
  
• how do you determine the correct RPM (20-25 Hz); is there a separate tacho (and LM2907?) installed on the generator, or do you sample input voltage ?
  
  

W.r.t. conversions, this system could work without a rewind for a lower voltage, i.e. using stockwinding. Simply build a new rotor and transform to whatever voltage you desire (12, 24, 48, ...). Downside is, you now have to deal with both the iron losses of the machine and the transformer losses. But in a site that regularly yields 15-24 kWh/day, I'd accept those losses with glee.

Anyway, one of the plans with the 10 hp conversion is to install both a temperature sensor and 'something' to determine RPM. Rather have it installed in the genny and not need it than need it and not have it. My main rationale was for star/delta switching though.

Peter.

[dinges]

Off-topic but possibly of interest to you, in regard of your last remark w.r.t. 3 phase motor drives.

Am at the moment also looking a bit into 3-phase VFDs (I assume that was what you were talking about?). Are you familiar with this IC (IR2130)? 10 E at my local supplier, she mailed me 3 hours ago. Even comes in good old 28-pin DIL version. Throw in some big transistors and there ya go ? Could it be that easy ?! If so, I may try to build one....

(tried to re-find the link but couldn't find it. Instead, have uploaded the Application Note AN985 to my files):

http://www.otherpower.com/images/scimages/3538/3_phase_motor_driver_an_985.pdf

Peter.

[oztules]

Hi Dinges,

 This will answer the above questions:

http://www.otherpower.com/images/scimages/5171/awp_1.html

This will give you a fair insight I think.

Dinges "W.r.t. conversions, this system could work without a rewind for a lower voltage, i.e. using stockwinding. Simply build a new rotor and transform to whatever voltage you desire (12, 24, 48, ...). Downside is, you now have to deal with both the iron losses of the machine and the transformer losses. But in a site that regularly yields 15-24 kWh/day, I'd accept those losses with glee."

Theory.... never mind the loss just put bigger blades to compensate and no problems.....

Practice....  problem with rewinds is that the pole number is usually small. This means bigger blades... lower freq, bigger tranny...... still do-able, but could get rather cumbersome transformers. However, still possible.

The beauty of the AWP is the 30 poles. low rpm, high voltage, high freq at these low rpms.

I'm sure you could add another foot to the prop and still have no freq problems.... (maybe furling problems and overunning etc, but no conversion problems)

The upside in transformer selection, is that while not very efficient at low freq, the power is low at this time as well. At cut in , only about 100w needs to flow through the tranny at low freq (25hz). As she gets more speed, the power increases and so to does the efficiency in the tranny as freq climbs to 80-90hz, so it all sort of dynamically matches itself.... if that makes sense.

With respect to drives...... thanks for your pdf, won't dilute this thread any further, but we should talk I think.

Maybe do a diary and ask for input from some smart folks here. think optoisolators and maybe 5 separate isolated (flyback with 6 output windings etc.) voltage sources for high side drives (3), low side drives, (1) and chip (1). for high current applications.

...........oztules

[(unknown)]

 A lot to think about in all the replies... Thank you.

@oztules: Thanks for sharing your experiance & providing the link to the "African Wind Power Review....." this gives me hope that I can find a low tech way to implement my plan. Most of the pitfalls are there to be seen... That said it seems to be a robust enough system... It has me thinking, & my revised idea is below.

@Ungrounded Lightning Rod & TomW: Both valid points, but we might be missing a trick by switching in the transformer... If you make a direct connection to the 48V controller until the voltage from the 220V generator gets to say 60V you get a fair wack of low current usable voltage that could be trickle charging the battery bank in low wind conditions... so it would not just be to get the blades spinning...

@Flux: No... my knowledge of electronics is not up to designing a floating input controlled voltage output PWM controller... only wish it was...LOL I am reassured that it wasn't a daft idea though... If somebody wanted to make some I'd certainly buy one from them though & I think there would be a market for the controller too... If correctly integrated you could have a controller that charged a battery bank & also grid tied, that would be a plus for anybody who required to keep a degree of independence but was happy to sell there excess... Would be of great use in area's were power outages are all too common... Like they are in Crete.

 OK... having decided I'm not up to designing the "Floating input controlled voltage output PWM controller"... I'm back to transformers, contactors (heavy duty relay) & a 48V standard controller... I have found that my max frequency is likely to be about 100 Hz at 400rpm... still waiting on some different performance graphs & pole counts...

 The plan:

 Custom wind 3 Toroidal power transformers to handle 1kVA each input. With 4 output windings I can run series, parallel or a mix giving we a range of output ratios this should also help with current handling as at max input all four windings will be in parallel...

 Control is going to be interesting though... If I direct feed the 48V controller from the generator from start-up I will need to switch in the series strung seconderies at say 60V in... I was thinking of using a trigger winding/s on the transformer for this with some simple zeners feeding transistors as switches for the contactor energising coils... will have to go away & think some more at this point...?

 I've been discussing this subject on a UK based forum & cross referencing to this forum to illustrate some points there... I hope Thats OK?  If anybody would like me to pull the links or remove the content please let me know.

http://www.navitron.org.uk/forum/index.php/topic,1934.0.html

  2kW 220V Turbine... Now:- Remote connection to 48V system.

 Once again, thanks for all the contributions & If anybody spots a commercial product that does the job please let me know...