Wire..Stranded or solid?

[Shadow]

I need a run of about 100 feet of cable from my tower to power shed, I have 3 wire #10 gauge stranded copper wire coming down the tower. (Dual rotor 48 volt,)But I ran out of that stuff. To buy new its 6.00 a meter. Thats about $180.00! So can I get away with using #10 or #12 solid copper wiring? House wiring? Rated for outdoor use?  Thanks

[ghurd]

It is common, and to most AC codes I believe, to use UF-B. It is solid. Sun light resistant, can be buried, suspended, etc.

Its like 'Romex' but usually grey or yellow. 2 or 3 conductor (not counting the ground).  Comes in #14, 12, and 10 that I know of.

Being common makes it a bit cheaper.

G-

[stephent]

"Get away with" ??

I won't tell if you don't.

[thunderhead]

The advantage of stranded wire is that it resists flexing more.  Solid wire that is regularly flexed will break.  

If you're burying the wire, stranded or solid makes no difference.  If you're suspending it, then it will swing in the wind, so it does.

[calchuck]

If you are talking about wire coming down the tower, I wouldn't use anything but stranded. The part from the tower to the power shed can be solid but I would tin the stranded wire ends and make the connection between the two with a split bolt and then tape them. For the lower voltages you need to keep the wire resistance down. 3M makes a poting compound to weatherproof this connection, make sure your wire is UV resistant.

[Sue Karber]

One advantage no one has brought up is that stranded will carry a higher amp load.

My 2 cents. Harold & Sue

[Shadow]

Here was my solution.. Local store had 100' 3 wire(16gauge) outdoor extension cords on sale for just over $20.00 each. So I bought 3 of them. Cut the ends off soldered the 3 wires together and now each leg of the  three phase from the turbine has its own 100' cord. I'm not sure what 3x16gauge works out to be but should be adequate.

[craig110]

Well, "adequate" depends upon how many amps the lines will carry and how much line loss you're willing to have.  How many amps is each of those phases going to carry both typically and (presumed) max?

Craig

[stephent]

Well, as long as top amps aren't above 20 amps er so, ya should be ok. (ignoring voltage drop)

Just going by the circular mills area you have the equalivalent of just better then #12.

Closer to a #11 actually. But using 3 strands of wire in parallel you MUST make sure each termination is very solid--like strip an inch of each conductor and solder them to a terminal. It's not pressure of the connection--it's the contact area.

Using crimp conncetors outside will give grief, pure and simple, unless soldered.

Now for the biggie--using the paralleled #16's and a 100' run will give a lot of voltage drop with more then 12 amps or so draw..

And the green ground wire is usually one size smaller then the hot/neutral wires--but it should just drop total wire size back to the #12 range.

Seal the ends of the cords outside well,,,the moisture will get into the end of the individual wires and travel back up inside the insulation and corrode the wires..the water will travel up inside the outer sheath too--use electrical grade silicone based goop to seal good.

[Shadow]

All good advice , Thank you.As far as amps go, I've seen 28 amps at about 60 volts from this turbine. So I'm presuming thats about 10 amps per phase.As far as wire size, all 3 are the same size. I was expecting the green to be smaller also. I soldered the 3 wires together and will be using a 220 volt receptacle on each end for connections.

[harrie]

Hi Shadow, I ran #8 three conductor under ground in plastic conduit 125 feet from my inverter. IT comes in to the house at 118 volts AC. I think I payed 120 bucks for a 100 foot roll. It is stranded.

[craig110]

At 10 amps through each of the 16ga wires, you'll drop/lose 8.3 volts (17%!) on each phase.  Running all three phases together (28A) through the 10ga would be a loss of 5.7 volts (12%).  Depending upon how badly you need every watt and/or the amount of money you've spent on the tower and genny, spending extra money to eliminate line losses can be very worthwhile.  It isn't as spashly as a bigger turbine or taller tower (who points out a fat buried wire to their friends? ;-), but using, for example, a 1/0 aluminum run to avoid the currently horrid copper costs would probably be in the hundred dollar range and lower your line losses to only 1.1 volts (or 2%).

There is a voltage loss calculator at the bottom of this page, http://www.powerstream.com/Wire_Size.htm, that is very handy.

Craig

[craig110]

Oh, I should have mentioned that these numbers are just for the 100 foot run to the power shed and don't include any losses due to the wire coming down the tower.

[Jerry]

As far as the higher resistance and voltage/power losses. Some of the GURUs here on the board talk about doing just that to some gennys to compensate for a genny to load missmatch.

As far as star conection you've allready got some resistance and voltage loss built into the genny. Some feel more resistance is a good thing?

You would think the higher resistance would alow the genny to spin up faster and compensate for some loss?

                         JK TAS Jerry

[wooferhound]

There is more information about Solid vs Stranded

in these stories . . .

http://www.fieldlines.com/story/2006/2/17/64130/3585

http://www.fieldlines.com/story/2005/7/19/153516/575

http://www.fieldlines.com/story/2004/12/23/03723/906

[DanB]

Hi Jerry -

"As far as the higher resistance and voltage/power losses. Some of the GURUs here on the board talk about doing just that to some gennys to compensate for a genny to load missmatch."

Yes, if the machine is such that resistance is so low that it stalls the blades then adding resistance downstream can improve performance a lot.  Consider the extreme case - imagine a system with 0 resistance (an alternator wound with superconducting wire) - then it would take an infinite amount of torque to increase alternator rpm above cutin rpm - the blades could never speed up.  On the other hand - if the alternator has infinite resistance then no power would be generated (or an infinitely small amount) and the blades would free spin.  Somewhere between is the 'best' match for the blades and often times this involves adding resistance.  My thinking with these machines lately is that it's wise to overbuild the alternator - you have to have resistance (heat) somewhere in the system, it makes sense to remove some of it from the stator I think.  There have been a few burnouts lately in 10' machines we made.  Some of these were not really the fault of the machine but rather the load it was hooked to.  A couple recently were the fault of the machine - 10' machines on very good wind sites and the bottom line was simply too much heat in the stator.  By using larger magnets - changing the coils a bit (fewer turns, heavier wire) I think we can lower resistance 50% without only a bit more cost in magnets.  But -  in order for those machines to run well in high winds we'll have to add resistance down stream.

"As far as star conection you've allready got some resistance and voltage loss built into the genny. Some feel more resistance is a good thing?"

Star -Delta -Jerry rigged doesnt even enter into it at all.  Wound for the same cutin speed with the same magnets then each way would be about the same.  Given the same magnet rotors - if I wound with Delta then it'd be lots more turns and thinner wire per coil.  In the end, if cutin speed is the same, so would resistance be.  It's not that 'more resistance is better' - its that we need the right amount.

Of course - with an electronic controller (some sort of PWM MPPT controller or something) then resistance could be extremely low and the controller would do the work of matching the blades to the load.  That's not what most folks are doing though.

"You would think the higher resistance would alow the genny to spin up faster and compensate for some loss?"

Yes, in some cases if the alternator was built to produce more power at a given rpm than the blades can produce, adding resistance helps.  

[DanB]

3 strands of #16 gage wire comes out to something about like 12 gage wire, not that heavy but probably up to the task in 'average winds' with some significant losses in higher winds.  If your machine tends to stall in higher winds then it may be a good thing.

I think you need to figure though that each phase is about 2/3 of your total current - not 1/3.

[Volvo farmer]

Hehe, that last story, two years ago, was mine.

I hooked up #10 solid to a 160W tracking solar array. It's been going back and forth with the sun every day now for almost a couple of years and the wires haven't broken (yet). Yeah, it isn't "right" but it works. Heck, the charge controller bit the dust before my "incorrect" wiring did. I'd not try this in a wind turbine tower but if you run big enough loops, the stress on solid wire appears to be within an acceptable limit, even on a tracking solar array, over many months of use.

[electrondady1]

guess it might be obvious but if wired it so the green were one phase and the black and white the other two, you could add as meney extension cords as you require to bring the resistance down were you  want it to be.

[Jerry]

Hi Dan.

Thanks for expanding on this and giving more insite to acttuly takeing addvantage of more resistance to improve wind generator preformance.

You mentioned some 10ft machines burning up. Are these the 9 12 combos? What are the typical voltage of the machinse? How many coils are involved in the typical burn up?

                          JK TAS Jerry

[DanB]

Hi Jerry -

There have been two recently.  One we built over 2 years ago (its been flying for 2 years) and its a brake rotor machine with 12 poles per rotor, 1" x 2" grade 35 magnets and 140 turns of #17 gage wire in each of the 9 coils.  The other machine is 1 year old but basically the same setup.  Both are in very good wind sites (better than were used to up here).  In the future I think I shall be using larger magnets and a lower resistance stator for those 10' machines - about $40 more in magnets and I can reduce the heat in the stator by 50% I think.

[Jerry]

Hi Dan.

Good plan. The lower resistance realy helps survival in those high wind conditions.

I was very pleased when my littel 8" dual rotor genny without furling survive the 68 to 80 mph winds for 6 HRs without a scratch. When I left the store at 6:30 that night the littel genny was doing over 1600 watts. Later that night there gusts of around 80 mph so the wattage must have been much higher.

What is so surprizing is the 9 coils are wound with 250 turns each of 22 gage wire and none burnt. All 9 of the littel 6 amp doide bridgres are fine also. ( stringth in #s I guse).

Merry Christmas and keep up the great work.

                       JK TAS Jerry

[Turbulent]

Just a little concerned about your curent draw figures on each phase for your cable run. I have tested on my own setup current draw on each phase, If you are getting say 30 anps DC then on each phase you will be about half an amp to 1 amp less on the AC side of it in current draw as I myself have an AC amp meter on each phase as well as on DC side, Mainly to see every thing was working properly, Mind you was surprized myself to see those figures ask a sparky friend of mine, did the maths and said it is about right, so just a thought to keep in mind. Don't know if anyone else has checked to see if it is simular or maybe it might be the type of confguration of the stator that might have somthing to do with it.  Turbulent