# 3 Phase Wind Turbine Wire Sizing?

Jayboy
Registered Users Posts:

**24**✭
Heya Chaps.

Trust all is well.

I need some help in the calculation of the recommended wire sizes for 3 phase Wind Turbine.

I'm looking to use a 1000W (Max 1200W) 24V Wind Turbine, About 25-30M away from battery.

3 Phase wire calculations are a bit confusing it seams. Can some one walk me through the calculation so I can apply it to all other smaller 3 phase Turbines too?

Thanks so much guys it would really help.

J

Trust all is well.

I need some help in the calculation of the recommended wire sizes for 3 phase Wind Turbine.

I'm looking to use a 1000W (Max 1200W) 24V Wind Turbine, About 25-30M away from battery.

3 Phase wire calculations are a bit confusing it seams. Can some one walk me through the calculation so I can apply it to all other smaller 3 phase Turbines too?

Thanks so much guys it would really help.

J

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## Comments

3,009✭✭✭✭Hi "Jayboy", welcome to the forum!

Question: Can you provide make and model of your wind turbine?

24✭Thanks

Its a HYenergy 1000W 24V

Regards

3,009✭✭✭✭http://www.smarthome.com/68121/WindMax-HY-1000-24-HYenergy-1000W-24V-5-Blade-Residential-Wind-Turbine-for-Low-Wind/p.aspx

OK, thanks, now we know what you're working with.

Before we go further - - what do you expect it to do for you once it's up and running?

Where will it be located, on a roof top? On a 100 foot tower? What is your real average wind speed?

Reason we're asking these questions, is because these types and sizes of wind turbines have hugely exaggerated power output ratings, and unless you happen to be located (really, not just hoping) in an extremely windy area, they all too often end up being expensive but pretty lawn orniments. Been there, done that, and I'm only one of thousands who have gone down that same road and learned the hard way.

In almost all cases, you'd be far ahead to spend that money on solar. There are many threads in this forum that speak to this exact problem with such turbines.

24✭Thanks so much for your reply and concern.

If anyone however could explain to me the calculation of wire size requirements for 3 phase power wrt to wind Turbines that would be great.

J

32,923adminThe ideal equation between 3 phase and single phase power is the sqrt(3).

_{3phase}= sqrt(3) * Voltage * Current (per phase) * Cosine (current vs voltage phase)So, one leg of current of a balanced three phase alternator will map to current after a full wave rectifier would be:

_{single phase}= 3^{1/2}* I_{one of phase leg}_{single phase}= 1.72 * 10 amps (three phase balanced current per phase) = 17.2 amps single phaseNote that rectifiers suppling a battery bank (relatively constant voltage) will be a "pulse train" of current (very high current peaks near sine wave peaks, no current when input voltage is less than battery voltage). Only a True RMS meter will accurately measure the "true" current flow. A non-RMS reading meter will (probably) over estimate the RMS reading (based on the mapping of sine wave peak voltage/current to RMS by a factor of srt(2)).

-Bill

24✭Thanks for this. I was reading up on the where this equation stems from. Trigonometry of the Y wiring. Makes more sense now. Thanks so much.

Could you give me a practical example of how much Current would be in each wire coming down from the turbine. How to calculate this, I very interested

Thanks, Can we use the 1200W 24V Turbine as example.

963✭✭Does the manufatuer suggest anything. I got recomendations when I built a turbine using hugh piggott's wind turbine plans. If it is the same turbine the link is for, seems to only be a 500 watt turbine unless solar is added with it. Only a six foot blade. Surly you can get what you need from the manufatuer.

gww

32,923adminSay the turbine was outputting 1,200 watts at 32 volts (battery+rectifier+wiring drop):

That would be my first guess... If you use an MPPT wind type charge controller, the turbine side voltages may be quite a bit higher (and lower current).

-Bill

24✭Thanks Bill. This make so much for sense to me.

This is a good equation:1,200 Watts * 1/32 volts * 1/1.72 = 21.8 amps per phase (AC Side)

Am I correct in saying that in each Wire Coming down from the Turibne Tower (AC side) : At Turbine Max Power there will be 22amps running through each of the cables at 32/1.72=18V V?

Thus 18V and 22amps per phase.

Totaling 1200W? (18x22)x 3

J

24✭I think I need to start here : http://www.windstuffnow.com/main/3_phase_basics

hehe

Thanks for all the trouble.

74✭✭The following cable sizes are recommended for the HYENERGY systems:

Distance from generator to controller

. . MODEL . . . . . < 150' . . . . 150' - 300'

HY- 400/12V . . . . 08 AWG . . . . . 06 AWG

HY- 400/24V . . . . 10 AWG . . . . . 08 AWG

HY- 600/26V . . . . 10 AWG . . . . . 08 AWG

HY-1000/24V . . . . 08 AWG . . . . . 06 AWG

HY-1000/48V . . . . 10 AWG . . . . . 10 AWG

HY-2000/48V . . . . 04 AWG . . . . . 02 AWG

HY-3000/48V . . . . 04 AWG . . . . . 02 AWG

32,923adminBecause of the "rotating" nature of the 3 phase power, they don't add up like three single phase cables.

In this case it is the current that is divided by 1.72 because the voltage was constant (as set by the battery bank).

If you have a constant current load (such as an arc light or arc welder), then the voltage would vary.

Also--Remember that AC voltage is usually measured as Root Mean Square. The actually "peak" sine wave voltage is srt(2) times higher than the RMS value. So--Your 32 VAC is really 32*srt(2)=45 volts peak. And the battery is really clamping that at ~30-32 volts. At that point, the alternator is going into current limited mode (you cannot expect an alternator to supply "unlimited" current at the voltage peaks).

It has been years since I played with motor math--And I have not worked with Wind Turbine Alternators--So I don't really know what the "real life" math looks like (non-linear outputs like voltage clamped alternators is not going to be very pretty math). I am just using estimates to get you kind of close.

Perhaps something like this place can give you more accurate information on turbine/alternator design:

www.otherpower.com

Midnite Solar has a version of their Midnite Classic MPPT charge controller (and a forum) where they can probably give you some design tips too.

http://midnitesolar.com/

Sorry,

-Bill "a person has to know his limits" B.

74✭✭The 1,200 Watt system is a 1,000 Watt Wind Turbine PLUS a 200 Watt Solar Panel. The 200 watts from the Solar Panel uses a seperate pair of wires to the Charge Controller. So, the amps in wires of the 1,000 watt Wind Turbine in 28 MPH wind is ...

1,000 Watts / 32 volts / 1.73 = 18 amps

1,000 Watts = 32 Volts * 18 amps * 1.73

32,923adminNote the 1.73 factor is from three wires (3 phase circuit) each carrying XX Amps to one pair of wires (single phase--or total output power like a heater or motor) carrying YY Amps

-Bill "just to be clear" B.

1,807✭✭With a three-phase wind turbine generator being rectified to DC for battery charging the conventional calculations for phase current in three phase motors and generators do not work. Basically, you have to figure that each leg of the three phase from the turbine is carrying the full amps 2/3's of the time when you're rectifying to DC and charging batteries. Therefore with battery charging wind turbines there is no downsizing of the wire on the three-phase vs the DC portions of the circuit in total circular mils. And transmitting the DC power is more efficient than transmitting the three-phase power since you're not dealing with capacitance issues with DC, charging the wire run twice with each complete AC cycle.

The wire run resistance of the three-phase portion of the circuit is double the resistance of one leg. This is because at any one time you have two conductors (and two phases in the generator) carrying the full amp load (DC out from the rectifier, plus power dissipated in the rectifier). Therefore the amp loading on the three-phase portion of the circuit is actually slightly higher than it is on the DC side of the rectifier.

If you measure the current on any leg of the three-phase portion, you will get .67 the value of the DC current from the rectifier. And if you measure voltage between any two legs of the three-phase portion you will get DC voltage plus 1.4V forward drop in the rectifier divided by root 2 (1.414). However what you are measuring on the three-phase portion is RMS values, not peak values. So the peak voltage and current is the same between any two phases or legs of the three-phase as it is on the DC side.

I always recommend making the three-phase run as short as possible - usually only down the tower - rectify at the tower base and run DC the rest of the way to the utility room. I don't like rectifying at the turbine because rectifiers are prone to failure in the severe duty environment encountered at the top of the tower. Also shutting down a high voltage turbine by using stator braking with DC coming down the tower is rather exciting due to the nice welding arc you can get with high voltage, high amperage DC power.

The size of the wire to be used depends on the length of the run and how much power dissipation you can tolerate in the run. If you size the wire small for the amp load a lot of power will be dissipated in the run, the turbine will run faster and at much higher voltage. If you size the wire larger, it is usually better. One of my turbines has a wire run of about 1,000 feet to the utility room. That turbine runs at 148 volts and 23 amps at rated output. The wire run is 2/0 aluminum buried underground and I get very little loss (~135 watts) at only 23 amps on that 1,000 foot run.

With even smaller turbines less than 3.0 meters in size and down to 2.5 meters I would not use smaller wire than 6 AWG, even on a short run on a 24 volt system. If the system is 48 volt I would not use smaller than 8 AWG. 12V turbines are close to being impractical unless the wire run is very short and large conductors because the losses become intolerable - unless you use a MPPT controller to get the wire run voltage up to reduce losses.

--

Chris

74✭✭IF the manufacturer's Charge Controller is going to be used then I think that controller should be located "indoors". I am not sure their controller can survive the humidity and/or temperatures at the tower. Maybe, a special enclosure can be used? The manufacturer's controller expects 3-phase power from the Wind Turbine since it has a built-in rectifier. That implies 3 phase down the tower and to the Charge Controller, where the controller is located nearer to the battery than the tower. Also, there is NO WARRANTY on the wind turbine if you use your own rectifier or different controller!

If the Wind Turbine is "used" and warranty is not an issue then Jayboy has much more flexibility in placing the various components.

So we need to know ...

Is the Wind turbine new with a mfr warranty or used without warranty?

1,807✭✭That may well all be. But that's bad design on the manufacturer's part. There is no electrical code that allows for ungrounded three-phase service from anything, with no neutral, to come into a building. And chances are the charge controller is not really a charge controller. Charge controllers perform bulk/absorb/float (and sometimes equalize) functions. More than likely it is the typical "dump load controller" that is used on most Chinese-manufactured wind turbines. Rectifiers and resistive "dump load" controllers are fire hazards and should not be located anywhere close to, or inside, of a building. Nor do you want an ungrounded three-phase power supply that's mounted on a 90 foot lightning rod coming into a building.

When it comes to off-grid wind power there's the right way to it, and the way it's usually done by the Chinese turbine manufacturers. So I digress.

--

Chris

74✭✭Jayboy,

OK, so know you know that you will push about 18 amps (+/-) in each of the 3 phase wires with 28 MPH winds. Typically, 12 AWG wire can handle up to 20 amps. BUT, the manufacturer reccomends that you use 8 AWG wire from Turbine to your controller (see table below) ...

. . MODEL . . . . .

< 150'. . . . 150' - 300'HY- 400/12V . . . . 08 AWG . . . . . 06 AWG

HY- 400/24V . . . . 10 AWG . . . . . 08 AWG

HY- 600/26V . . . . 10 AWG . . . . . 08 AWG

HY-1000/24V . . . . 08 AWG. . . . . 06 AWGHY-1000/48V . . . . 10 AWG . . . . . 10 AWG

HY-2000/48V . . . . 04 AWG . . . . . 02 AWG

HY-3000/48V . . . . 04 AWG . . . . . 02 AWG

You know WHY you should use the 8 AWG wire vs 12 AWG wire, right?

1✭