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Homebrewing a Three Fase Generator

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MRacerxdl

Wed Aug 26 2009, 03:43AM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

I am planning to make in next year an wind turbine or something so. And I am thinking about planning the three fase generator.

I have seen a lot of designs over the web (including 4hv) and I see that mosts uses low voltage/high current coils on the generator. Is there any reason for that? I was thinking about make something to generate 300VDC with 3A instead 10V 90A, that is thinner wires and less heat dissipation on regulators. Is there any problem doing like this?

Other question is about of the speed of the generator. As I think as the generator runs faster (in case a wind turbine, it gets more wind speed) the frequency output goes up, that is correct? If so, the best thing is to retificate the three fase and made a Syncronous 60Hz Sine Inverter to have Mains Like output.

Someone who already made something like that, if can help me I will be grate =D
That is a next year project, as I have a few projects to this year (three fase brushless motor inverter, and a Digital Amplifier Protection Circuit and Managent), but I think its better to starting planning this before, as if its a wind turbine, it will be alot expensive. I planning to made a few low-scale tests with HDD Magnets and some small coils to test it before made something bigger.
Thanks =D

IamSmooth

Wed Aug 26 2009, 04:30AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

welcome to the party!

you have a long road ahead. The best immediate advice is to check out this website that has a lot of information:

A help forum (like this one) for RE is here:

There is no problem with higher voltage. It all depends on your goal? battery charging or grid-tie? If the former, you want lower voltage around 12v, 24v or 48v. If you are going into an inverter you have to consider what is the maximum voltage the inverter will take. You need to make sure your generator will never exceed this voltage. This is usually accomplished with a shunt controller that goes to a dump load.

Frequency does not matter with wind speed because you will rectify and smooth whatever output you get. You will then take this output and go to a battery bank, inverter or grid-tie inverter.

You will also have to consider how much power you plan to get and at what average wind speeds. You will need to plant anchors and build a *safe* tower. You also need to consider the highest possible winds in your area and if your tower will be able to withstand that thrust load. This affects the prop size you choose. You will need to protect your generator from overspeed conditions (very high winds). This is accomplished with furling the prop out of the wind, changing the blade pitch or having a centrifugal governor.

Check out my web diary at

I've been down this road and I'm still walking on it.

MRacerxdl

Wed Aug 26 2009, 03:29PM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

Last night I saw pratically all your site =P

I am planning to made a wind turbine to get the lamps of the house turned on, as I dont have much lamps and they are only 20W (Fluorescent bulb) I think here I will have 300W of lamps or so (I will calc it later before made the wind turbine).

I plan to made an sort of grid-tie, but a little different:
When wind generator is running good and can supply the lamps, the lamps are only supplyed by the wind generator and charges a nobreak (basic its a battery, but I choose a nobreak, because that I wont need to make a battery charger circuit and inver from 12VDC->110VAC), when it cant run the lamps, it will run the nobreak until it have battery, when the battery is about to get discharge, one relay turns the nobreak on the mains line to charge it again.

If there is enough wind here, and the wind turbine can run things good, there will never a connection between the nobreak and the mains. But as wind is never the same every day, I need to think that too. The nobreak with my current batteries can handle it for hours, so it might be good making a wind turbine.

I am starting with a "low size" project, as 300W because its my first of this type, and I am making for tests, that is because I will put only lamps on it.
The only thing that I dont know now, is how tall I will put the wind generator, I live on a high place, but its a residencial place. That is not a big problem, I have good winds here, but it cant be too much taller because I have an near airport here (some about 1km away, I can see it from my window), so everything here can cause me problems =P

I thinking about 2 or 3 meter up to my house roof. All houses here are constructed with concrete and steel, but mine have some sort of nice walls and so that can handle very high loads, so if I made a good "weld" of wind turbine base, I wont have much problems.
With 2 meters up to the roof, I will have some sort of 6 meters, far more high than other things here, luckly I dont have any high building as neighboard =P

IamSmooth

Wed Aug 26 2009, 05:18PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

do not attach your turbine tower to the house. you will get low frequency vibrations that will drive you crazy. others at the websites I offered may have more things to say. You will need to clear your roof top.

As far as size, I have a 10.5' rotor that on an average day makes 100watthrs. I am hoping for more in the winter. When I get higher winds it can make close to 2kw every hour; however, you design for your average winds. If I lived on a farm and wanted to run a significant portion of my house, I would need a rotor close to 30-50'.

If you go ahead with your battery scheme you will find that you are depleting your battery frequently and then depending on your mains. A better idea might be to pick and isolated circuit in your house, charge a battery bank and run this circuit of of the battery. Find an off-grid inverter than you like and determine what battery voltage you need for it. Then design your alternator to achieve that target voltage (cut-in) when the winds are at the 5mph range. You will have to determine the rpm of the alternator and the rotor size that will achieve this.

For example, my 10.5' rotor spins near 80-100 rpm in 5mph winds. I designed my alternator to hit 70v near this speed because that is the voltage required by my alternator before it starts extracting power for the first time.

Available wind power increases with the square of the radius and the cube of the wind speed. Keep this in mind. Good luck.

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