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Too much power
By Chuck, Section Homebrewed Electricity Posted on Thu May 13th, 2004 at 04:06:51 PM MST
convoluted power inputs

OK, I've succeeded in getting myself into a bit of a technical bind and thought I'd troll for some advice.
I just purchased a really sweet old wind machine. 3kw and 140 volts DC. However, my battery system is 24VDC and I'm off the grid. I'd really like to use this baby but I'm going to need to modify the output to do so or I could fry the windings. So far I have come up with a few concepts.

Get a really big MPPT controller and try to rig a dump load that kicks in somehow. I'm not sure such a thing exists that would work for a wind machine. Outback power is working on it, but it's a low priority they say. This would need to handle over 150 amps of output amps (at 24v).
Rewind the generator to put out a lower voltage. (big fat wires) It seems a shame, but it might be the easiest way to go.
Run the wind generator into a couple "Windy Boy" inverters that pick up the "grid" from my Prosine 2500 inverter and let them charge the battery via the Prosine's built in battery charger. This sounds really convoluted and I'm not sure it'll work. But sometimes it seems logical. Other times it's just too circular.
So, any other schemes that might work ? I know I'll have to get a big dump load in any case. I'm thinking hot tub. ;) I don't know of a dump load controller that'll handle that kind of power either, so maybe dumping at the 140v DC level would be more prudent.
Thinking out loud...
Chuck

Too much power | 24 comments (24 topical, 0 editorial)

Re: Too much power (none / 0) (#1)
by drdongle (Dr.Dongle1@juno.com) on Thu May 13th, 2004 at 04:31:27 PM MST
(User Info)

Do you have a manual and or schematic? if so check to see if the out put is AC and then rectified to DC, you could take the AC out put ( or outputs if 3 phase) and run them to a transformer and reduce it to 30 V so as to charge the batteries, or if the generator/ alternator has a field coil that excites the system reduce the field coil voltage to an out put more suitable to charge your system.

Carpe Vigor
Dr.D
Carpe Vigor, Dr.D

Re: Too much power (none / 0) (#2)
by laskey on Thu May 13th, 2004 at 04:37:39 PM MST
(User Info)

I know this sounds crazy...but ... find yourself a 140 volt DC motor that can handle 3kw and use that to turn a 24 volt generator that will produce something like 3kw, and use that to charge your battery bank. Use a space heater or a hot water tank element as a dump load.

Cya,
Chris

Re: Too much power (none / 0) (#3)
by TomW on Thu May 13th, 2004 at 05:01:18 PM MST
(User Info)

Laskey, Dr. D.;

Hehe stole my ideas while i was thinking on it. Haha. Those were the top 2 off the wall thoughts I had [dc motor driving generator or a transformer]. Great minds think alike, I guess.

Cheers.

TomW

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

Re: Too much power (none / 0) (#4)
by DanB (danb@*no spam*otherpower.com) on Thu May 13th, 2004 at 05:46:14 PM MST
(User Info) http://www.otherpower.com/

Hi Chuck -
sounds fun!
Is it a wind generator??... what sort is it?

Re: Too much power (none / 0) (#8)
by Chuck on Thu May 13th, 2004 at 10:14:51 PM MST
(User Info) http://home.morrisonprairie.com

I'll try to answer a bunch of comments here. Yes, it sounds like a Jacobs and it is. So it's definately a generator and I can't do easy solutions like using a transformer to change the voltage. I haven't picked it up yet and so don't know if there are any docs with it or not.

I did think about getting a motor/generator combo to charge at ~24v. Since it's 100+ VDC I'd probably have to rig something up unless the driving motor was a universal type. Make that concept #4. I'll still have to get the hot tub for the dump load.

Thinking about the variable shunt idea... It sounds ok until realizing that it cuts the available power from 3600 watts to around 800 watts. A nice thing about a high voltage unit is the ability to transfer a lot of power with reduced amperage. The bad thing about that is reduced amps means going the other way you loose a lot of capability.

I'll look into the sunny island concept some more.

Thanks for the thoughts.

[ Parent ]

Re: Too much power (none / 0) (#5)
by Victor on Thu May 13th, 2004 at 06:07:28 PM MST
(User Info)

Hi Chuck,

Regarding solution 3, systems like this have been done ( called Sunny Island) SMA has a stand alone inverter in europe that they can run this way. I think the AC buss is envisioned for connecting multiple charging sources in a village power system.

I have heard of some one doing it with a windyboy and an outback inverter, he was applauded for risking his own dime and pulling it off.

I have serious doubts about the bidirectional power capability of the Prosine inverter in this application and don't think it would work. I also think the not working part would result in a lot of smoke and $.

Sorry I can't think of any good solutions.

It sounds like you may have an old Jacobs, Yes? If so you may be able to find some one with a low voltage model who wants to trade.

Good Luck
Victor

Re: Too much power (none / 0) (#11)
by DCJake on Fri May 14th, 2004 at 06:29:51 AM MST
(User Info)

Chuck,

I know someone who would probably trade you the 140V for a 40V short case. You would have to take a road trip to Oklahoma. He is a Jacobs nut, he's currently flying 4 of them. He peaks out at 240 amps @24V.

Which governor to you get? How complete is it? Mick Sagrillo has lots of parts available if you need them.

I'm putting up a short case later this summer here in Colorado.

I have copies of the original owners manuals if you need them.

Kevin

[ Parent ]

Re: Too much power (none / 0) (#12)
by Chuck on Fri May 14th, 2004 at 07:23:57 AM MST
(User Info) http://home.morrisonprairie.com

Hi Kevin,

Thanks for the tip. I'll let you know when I get possession of it and can see what I'm really dealing with. There seem to be lots of options.

So where in Colorado are you putting it up ? We could compare notes. I expect to put this up sometime this summer as well, probably while waiting for a building permit to get approved.

Chuck

[ Parent ]

Re: Too much power (none / 0) (#14)
by DCJake on Fri May 14th, 2004 at 07:52:41 AM MST
(User Info)

Chuck,

I'll be putting it up about 5 miles NW of Idaho Springs.

What type of tower are you considering?

Kevin

[ Parent ]

Re: Too much power (none / 0) (#15)
by Chuck on Fri May 14th, 2004 at 08:30:53 AM MST
(User Info) http://home.morrisonprairie.com

Ah, up in the mtns and not all that far from here. Let me know when it happens.

Mine will go up about 12 miles E. of Greeley.

There is a tower with the Jake. I'm expecting to use it. I believe it's a 3 leg style. Angle iron and very heavy I'm sure. What are you using for a tower. These things are really heavy.

Chuck

[ Parent ]

Re: Too much power (none / 0) (#19)
by DCJake on Fri May 14th, 2004 at 12:16:39 PM MST
(User Info)

Chuck,

I plan on using a 80ft Rohn 45G.

I'll be in Greeley towards the end of the month for work.

Kevin

[ Parent ]

Re: Too much power (none / 0) (#6)
by Ungrounded Lightning Rod on Thu May 13th, 2004 at 07:17:44 PM MST
(User Info)

Check whether the motor has multiple windings that can be connected in different configurations to get different voltage/current tradeoffs.

Re: Too much power (none / 0) (#7)
by Ungrounded Lightning Rod on Thu May 13th, 2004 at 07:19:19 PM MST
(User Info)

Check whether the motor has [...]

ARGH! I meant generator. (That'll teach me to preview.)

[ Parent ]

Re: Too much power (none / 0) (#9)
by Jerry on Thu May 13th, 2004 at 10:50:25 PM MST
(User Info) http://www.dplusv.com/Photo-03.html

Hi Chuck

I'm doing the motor thing. I couldn't aford the very exspecive invertor for my 250ft well. Its a one HP 240 vac well pump.

So I'm using two 2 HP DC motors to run a 5KW belt driven genorator. This works very well. These morors are 100 VDC motors. I've ran them up to 300 vdc no poroblem. They weight about 85 LBs each.

I have a few extra $75 each. I also have a 4 KW 120/240 generator that could work with these motors for $50.

Just an idea?

JK TAS Jerry

Airheads Page

Re: Too much power (none / 0) (#10)
by John II (jjones2(at)inetvisions.net) on Thu May 13th, 2004 at 11:45:52 PM MST
(User Info)

Jerry..... I'm fascinated by your comment about motor to generator to run your well pump. I'm in the process of doing the same thing with a 1/2 hp at about the same well depth. A couple of questions...

Your pump can handle wild ac voltages and frequencies ? Or do you have someway to keep it in "a safe zone" ?

Are you pumping into a pressure tank or gravity ? All of the info I can learn from you may save me $$$ which is getting a little hard to come by : ) so will be greatly appreciated. Email me if you like.

And Chuck... I'd really think twice before I rewired your Jacobs or messed it up. I originally set up for 12v A.E. and now have so outgrown it... that I'm trying to set up a 2nd system for 120vdc... which I think I'm really going to like... no more wires the size of garden hoses !

Also... have you considered a DC to DC converter like what some of the guys on this forum are building to build high powered inverters ? They look relatively simple, and could be used to step DC down just as eaisly as they are using to step it up. Perhaps you could get one of them to build you one ? I'm guessing that would be the efficiet way of getting your voltage stepped down from your wind genny.

[ Parent ]

Re: Too much power (none / 0) (#17)
by Jerry on Fri May 14th, 2004 at 10:42:06 AM MST
(User Info) http://www.dplusv.com/Photo-03.html

Hi John 11

The generator is a free standing belt driven 120v/240v, 60 HZ VAC 3600 rmp. It was designed to be driven an 11 hp gas or equal engine, gas, diesel, steam and ect.

I've been told electric motors hp ratings can be doubled when compaired to gas engines? So I tried it. It works great. I,m also running these motors at 240 volts dc.

I'm using 20 small garden tractor batteries for the 240 VDC. I'm using a 400 amp aircraft relay to swich power on. I've placed a 4UF/1000 volt cap accross the relay contacts to suppres arching.

When this system starts up the no load voltage is 260 VAC. As soon as the pump kicks in it drops to 240 VAC and holds rock solid.

At first I tried my 3500 watt sinewave inverter but it woudn't handle the startup load and triped off.

An inverter that was strong enough to start the pump was way to exspencive. Since the pump does not run continually this motor setup works just fine.

The motors have 6" pullies and the generator has a 4". Generators are available at 1725 rpm also. This cut the requiered rpm in half wich could reduce rpm and voltage needs also.

You could use smaller pulies on the motors. This would reduce the stress on the motors. These motors are rated at 1750 rpm at 100 VDC at 2 HP.

JK TAS Jerry

Airheads Page

[ Parent ]

Re: Too much power (none / 0) (#18)
by Jerry on Fri May 14th, 2004 at 10:53:11 AM MST
(User Info) http://www.dplusv.com/Photo-03.html

PS.
Tred mill motors could work for this application also. I might have to try this.

A freind is in the tred mill busines and I get a few used 2 HP and 2.5 HP 130 volt 3,050 RPM motors on ocasion.

I've been building wind gennies with them but two of the 2.5 hp on my 4 KW ac genny might proove intreeging?

And there rpm range is closer to the gennies 3600 rpm needs. The pullies would be closer in size? And the voltage would be lower? Fewer batteries? HMMMM.

JK TAS Jerry

Airheads Page

[ Parent ]

Re: Too much power (none / 0) (#22)
by Chuck on Fri May 14th, 2004 at 06:57:01 PM MST
(User Info) http://home.morrisonprairie.com

Yes, well... having rewound a couple much smaller generators a few years back, rewinding this beast is not my top choice. My system is 24 volts and could conceivably become 48 volts without buying anything new except an inverter.

I do like the idea of a DC-DC converter, which is what the generator-> motor-> generator idea is. Only without solid state components. I'll look into this further for sure.

Chuck

[ Parent ]

Re: Too much power (none / 0) (#13)
by Chuck on Fri May 14th, 2004 at 07:30:48 AM MST
(User Info) http://home.morrisonprairie.com

Jerry,

Thanks for the example. The motor is good possibility, although I'd need to match it with a 24v generator to charge the batteries, unless I could use the prosine charger side.

In a way using a motor at the other end is kind of like using an air compressor or hydraulic pump on the wind genny side. It's doable. It just takes a bit more stuff to make it work.

I'll let you know if I decide to go that way.

Chuck

[ Parent ]

Re: Too much power (none / 0) (#16)
by windstuffnow (elenz(at)windstuffnow(dot)com) on Fri May 14th, 2004 at 10:06:42 AM MST
(User Info) http://www.windstuffnow.com/main

Here is an odd thought... What would happen if you fed the high voltage directly into a battery charger? Would it handle the variable AC input?
If its a 3 phase unit you would have to somehow convert the output to single phase... is this possible?
Interesting idea....?

Have Fun
Windstuff Ed

Have Fun! Windstuff Ed

Re: Too much power (none / 0) (#20)
by zubbly on Fri May 14th, 2004 at 04:49:17 PM MST
(User Info) www.zubbly.com

hello Chuck!

If your genny is 3 phase before being rectified, i may be able to give you some instructions on how to re-connect the winding with more parallel connections to drop the volts down. Possibly someone who is familiar with this genny may know for sure what the actual winding is.

zubbly

Re: Too much power (none / 0) (#21)
by tecker on Fri May 14th, 2004 at 06:54:05 PM MST
(User Info)

Bypass the rectifier and runit through a transformer with a multitap to get what

you want then rectify

Re: Too much power (none / 0) (#23)
by hvirtane (hannu_markus_virtanen(at)yahoo(dot)com) on Sun May 16th, 2004 at 01:30:26 PM MST
(User Info) http://web.archive.org/web/20050404022706/www.cc.jyu.fi/~hvirtane/cooker/

Bypass the rectifier and runit through a transformer with a multitap to get what
you want then rectify.

I would advice the same.

The other possibility in my opinion is to
do what 'WindstuffEd' said. Run the three phases
separately to three battery chargers and use them
to charge batteries.

- Hannu

Re: Too much power (none / 0) (#24)
by kell on Mon May 17th, 2004 at 12:06:36 AM MST
(User Info)

A buck (step down) converter would do the trick with very high efficiency. A buck converter running in continuous mode at a duty cycle of about 20%... You would need a heavy inductor, which could be the line side of a salvaged microwave oven transformer. IRF740 mosfet for the switching. A 555 timer, a couple of resistors and a capacitor sets the frequency and duty cycle. Besides that stuff, the basic buck topology only calls for a diode and a filter cap.

Too much power | 24 comments (24 topical, 0 editorial)

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