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120VDC down to 48VDC converters out there??
By ve7khz, Section Controls Posted on Sun Sep 16th, 2007 at 06:57:27 PM MST
Looking for 2:1 voltage drop

There is a proliferation of 120VDC wind turbines out there now, and I want to play with them, but the output from their controllers (which control the tail to turn them out of the wind) is 120VDC, a bit too high to properly charge a 48VDC battery bank. Has anyone played with charge controllers that would accomplish this? I have been looking at Outback's MX60, Xantrex XW controller and a couple of other ones. I can't seem to get a definitive answer from anywhere, if any of these solutions will work.
I'm not sure exactly, how the turbine controller's output voltage is regulated, if at all. The one I am looking at is a chinese built 2KW unit.
Your thoughts on a good solution to get 120VDC down to 48VDC-60VDC for battery charging would be appreciated.
Cheers
Paul

120VDC down to 48VDC converters out there?? | 12 comments (12 topical, 0 editorial)

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#1)
by Kevin L on Sun Sep 16th, 2007 at 02:20:26 PM MST
(User Info)

Correct me If anyone has different information but converting power from 120 VDC to 48 to 60 VDC is not very feasible without large losses in efficiency. You would be better off to change to a 120 VDC battery bank, or stay with the 48 - 60 VDC mills. If you pull the AC power out of the generator though, you could run thru a 2:1 transformer to provide 60 VAC which could then be regulated to DC. Kind of a waste of the regulator in the mill as it will only be supplying power for the controller.

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#2)
by wdyasq on Sun Sep 16th, 2007 at 06:57:58 PM MST
(User Info)

The AC would need to be in the frequency range of the transformer for it to work properly.

Ron
Adventure is just bad planning." -- Roald Amundsen
[ Parent ]

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#5)
by jacquesm (j@ww.com- I run a whitelist, add 'stjoes' to msg) on Sun Sep 16th, 2007 at 08:02:23 PM MST
(User Info) http://www.greenbits.com/

if the windings are exposed you could try to parallel two sets of them instead of running them in series. If the windings are not exposed then you will be spending a lot of money or you will have to get a different mill.

Most commercial mills are based on 'standard' motor frames and are wound for a specific output voltage with each phase as a continuous coil, but sometimes you get lucky and the windings are exposed in sets of several coils.

The reason for that is that some manufacturers sell windmills in a variety of voltages and the easiest way to do that is to manufacture just one set of coils and hook them up in different configurations depending on the application.
www.greenbits.com
[ Parent ]

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#3)
by robl (rob_linschoten@telusDOTnet) on Sun Sep 16th, 2007 at 07:11:30 PM MST
(User Info)

Hi Paul

Having had a 120VDC system for about 18 years (switched to 48 just a few years ago) I can vouch for the relative efficiencies these systems can attain, simply because so much stuff runs right off the 120V.

In any event, you will find lots of very efficient switching-type dc supplies out there, both new and used. For new I was using Samlex supplies. They are ostensibly 120-240VAC, but if you look at the specs you will see many of them will also run at 120VDC. Ditto for Kepco, Power-One, etc. Also true for Liteon, Toshiba, HP laptop-type switching power supplies running at 7.5 or 15V out.

Regards

Rob

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#4)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Sun Sep 16th, 2007 at 07:25:50 PM MST
(User Info)

GET A PFC regulated PWM 48 volts output power supply and adjust it for desired out voltage.

BUT you need to regulate the output current depending on the mill generator output voltage.

Nando

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#6)
by jacquesm (j@ww.com- I run a whitelist, add 'stjoes' to msg) on Sun Sep 16th, 2007 at 08:22:30 PM MST
(User Info) http://www.greenbits.com/

hey there Hernando, old champ, you don't give up do you ?

"GET A PFC" yes sir, right away sir, money of course no object... we'll get one ordered in immediately. The caps lock key is just to the left of the 'a' on my keyboard, if you press it once the little led thingy on the top right of your keyboard will go off and you will no longer need to hold down the shift key to get regular letters.

PFC = power factor corrected iirc

48 volts output is not going to do much battery charging now is it, when the batteries themselves are at 48 V there will be 0 flow... So you need a bit more, possibly quite a bit more, especially if you plan to do equalization charging from the mill. Not usual for a 48 V DC out supply to be 'adjusted' up another 12 volts. That's why the original poster asked for something that would do 60 Volts, which is not equal to 48 Volts.

Isn't that what mppt is about anyway ? oh what am I thinking, you're an expert in the field.

So, how about this then, you go do some hunting about where you can get a 120V DC to 48V DC +- 12V PFC regulated power supply, in the 2 KW range. I'm sure that's a run off the mill item you can go and buy in any store but strangely enough I can't seem to find any after a good bit of searching. DC to AC in that power range is fairly common, but DC 120V down to 48V is not all that common, if it is commercially available at an affordable pricepoint at all.

Have you apolgized to TomW yet ? It really is not going to go away until you do you know...

lost the link ? Here, let me help you: http://www.fieldlines.com/story/2007/9/15/154035/292
www.greenbits.com
[ Parent ]

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#7)
by ve7khz on Mon Sep 17th, 2007 at 12:59:17 AM MST
(User Info)

Thanks guys!

A few good ideas...

The other road I could take is to get a 120VDC - 120 or 240VAC grid tied inverter, then feed that into grid. I also haven't been able to find any of these...except in China. I already plan to install a grid tied inverter from Xantrex or Outback, which will take care of battery charge, battery backup and load dump. Mainline mfrs like Xantrex, Outback etc. seem to only go to 48VDC in their regular line up.

The reason I am looking at the Chinese 2-5KW turbines, is that they are priced right, compared to Bergey or SWWP etc., and seem to have the overspeed control taken care of by the controller. They all have FRP blades, aluminum housing, rare earth magnets and look to be relatively well built. Also gets me generating right away...as build time is scarce these days. :-(

Any thoughts on this route?

Cheers

Paul

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#8)
by TomW on Mon Sep 17th, 2007 at 06:18:26 AM MST
(User Info)

Paul;

There are a few things I would avoid at all costs:

Flying on a Chinese built anything

Flying a Chinese Airline regardless of the aircraft make.

Mounting large Chinese built rotating objects high in the air.

Wearing a $5 Chinese built wrist watch is one thing, trusting life and limb to something they built is quite another.

Not bashing China. All you have to do is be current on events to know they can't be trusted to use safe paint on toys, make safe food for either humans or pets, so I sure don't trust them to use properly built and graded bolts to hold things together. Not to mention castings with massive sand pockets and voids.

Your mileage may vary but just ponder the above a minute. Especially where safety is a concern you do not want things built "to a price" by bronze age level manufacturing.

Of course, these are just my opinions and may be of no concern to you.

Good luck with it however you decide to proceed.

Cheers.

TomW

"Education consists mainly of what we have unlearned."--Mark Twain
[ Parent ]

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#9)
by ve7khz on Mon Sep 17th, 2007 at 09:37:30 AM MST
(User Info)

Hi Tom,

I hear ya. All valid points, and I too have had these thoughts...

My current thinking is to get one unit and have it erected a fair distance out back in the clear, monitor it for the winter and drop it once in a while for inspection, then once it is confirmed to be good, pick up a couple of more. If there are problems, then it will not be a total loss, and a good learning experience. The 2KW units are right around $800 and the controller, which has load dump, shunt and shut down all automatically controlled, is about $160. Shipping about $120. Not bad for a 2KW unit.

If anyone is interested, I can report back in the apropriate section on my experience with it.

Thanks for the thoughts.

Paul

Oh, BTW, I found a few manufactures that supply controllers that output 48VDC, not just 120VDC.

[ Parent ]

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#10)
by geoffd on Mon Sep 17th, 2007 at 09:46:43 AM MST
(User Info)

I use an MX-60 to convert nominal 48 volt to 24 volt. My PV's are wired in series and I have seen 70+ volts out of them. The batteries are nominal 24 volt and the MX steps the power down with very little loss.

A friend of mine uses an MX-60 with a 120VDC hydro turbine and the only problem he has is when he has an excess of water and the input goes over 150VDC. The MX-60 shuts down due to too high input voltage.

So it can be done with an MX-60.

Cheers
Geoff

[ Parent ]

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#11)
by ghurd on Mon Sep 17th, 2007 at 10:44:01 AM MST
(User Info)

If it is of a decent design, shouldn't it be brushless, 3-phase, and wired in star?
So it shouldn't be too hard to reconnect the coils in Jerry-Rig or parallel Jerry-Rig to get the voltage lower and closer to a `normal' voltage.
For what I have done (nothing on this scale), they work a lot better if the coils are reconfigured when the voltage is too high at the beginning. The same principles should apply.

The Chinese stuff tends to look better from a distance. That's why there is rarely a close-up photo.
Example. This looks a few decades before the Bronze Age. Started with miscellaneous ferrous garbage, cast in some guy's garage, finished with an angle grinder, and painted with `dollar store' spray paint?
I like how the power wires are exactly the same color as the housing. None of those crazy black and red wires to get confused about!
http://www.promuster.com/china_professional_tools_products/generators_view.asp?editid=578&editid 2=&editid3=&TargetPageNumber=5&todo=readonly&masterkey=

Chinese factories make what they are told. If the manufacturer wants a good product, they are not cheap. If the manufacturer wants the cheapest unit possible, the factory will make that too.
I have some items with the same specs, both made in China. Some are nice, some are junk. The difference is the price. Inverters come to mind, Big-name quality = big-price, and No-name = cheap-on-eBay.
G-

[ Parent ]

Re: 120VDC down to 48VDC converters out there?? (3.00 / 0) (#12)
by robl (rob_linschoten@telusDOTnet) on Mon Oct 1st, 2007 at 11:00:46 PM MST
(User Info)

Paul

I have bought and used Exeltech 120 VDC in inverters with great success. They are well-built (in Texas I think), sinewave out and reasonably priced. Their larger units are stackable into the ten's of KW out.

Regards

Rob

[ Parent ]

120VDC down to 48VDC converters out there?? | 12 comments (12 topical, 0 editorial)

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