Author Topic: high volt coils (Read 1895 times)

Kid · « **on:** July 10, 2009, 04:15:08 PM »

I took some #24 mag wire and did a little test to see what voltage I could get so I wound 2 strands 236 times thinking more the windings more the voltage. I tested it on my 17ft turbine at 85 rpm and was getting 4 volts, using the formula to see what a complete stator would produce I came up with 29 volts. I guess my assumption was more the windings the higher the voltage. The coil fits inside the design just fine;What am I missing here?

SparWeb · « **Reply #1 on:** July 10, 2009, 03:02:52 PM »

Not exactly sure what you did, but some things that generally come up:

Is your multimeter lying to you? (they can, you know)

Is it able to read what you want it to? (they aren't all created equal)

Do you have axial flux dual-rotors face-to-face?

How have the two coils been connected together? (in series or parallel?)

Do the 2 strands turn the same way? (or are they backward?)

Have you checked the coil for shorts? (nicked the insulation varnish?)

That many turns of 24ga wire should have several ohms resistance.

Onthero · « **Reply #2 on:** July 11, 2009, 04:05:17 AM »

(try to replace your battery of your multimeter, mine gives the strangest readings with an almost empty battery)

Flux · « **Reply #3 on:** July 11, 2009, 02:50:46 PM »

I have just come back after an event and I am too tired to sort through all the data on the 17ft machine.

As far as I can remember it is 16 pole so you have done something wrong with your calculation.

4 coils in series gives 16v then x 1.7 for phase and x 1.4 for mean dc gives about 38v not 29.

Even so this seems very low. I assume the 17ft machine is 48v and the normal winding is about 60 turns but I can't remember the intended cut in speed.

As others have said you don't give a clear indication of what you have really wound.

You imply 236 turns of 2 in hand but the way you describe it I can't be sure but if that is right you seen to be in error by a factor of about 4.

Check your meter readings and battery as others have suggested. If you still get the same figures come back with full details of the magnets, and other details and ideally give a picture of your coil. I suspect you are doing something wrong.

Flux

imsmooth · « **Reply #4 on:** July 13, 2009, 05:48:26 AM »

I've wound my stator for high voltage, and I see a linear relationship with the number of turns and the open voltage for a fixed RPM. Are the coils connected to eachother the correct way? I think you will have to try again.

Kid · « **Reply #5 on:** July 13, 2009, 09:17:26 AM »

I have one test coil set up with a meter attached to the start of the coil and the finish of the coil. I have not built a stator yet just one test coil. I have the single coil secured between my magnet rotors and I am spinning the rotors by hand and I have a digital tachometer monitoring the RPM. The rotor is the 16 pole and I originally had the stator set up as a 48v system. I am experimenting with 24 ga. Wire to see how much voltage I can produce with my 17ft system if I were using 24 ga wire. So I made a single coil out of 24 ga. Wire and wound it 236 times with 2 strands of 24 ga. wire. I spun the rotors at 85 rpm and took a reading with the meter; here is the formula I used to calculate what I should get from the system if I built a complete stator. I am not sure if I am calculating this correctly.

4 volts x 1.4 = 5.6 x 4 = 22.4 x 3 = 38.79v

This is only an experiment to determine how much voltage I could get from this system using 48 ga. wire and utilizing the space available with this system. Would I get more voltage if I were to use 4 strands of wire and cut my windings down to 118 turns? or would it stay the same and give me less resistance? would it give more voltage with one strand wound 472 times?

Kid · « **Reply #6 on:** July 13, 2009, 09:21:51 AM »

oops another mis calculation looks like i should be getting 67.2v not 38.7v.

imsmooth · « **Reply #7 on:** July 13, 2009, 10:26:48 AM »

I don't know why you are using two strands of 24. Why not use a thicker gauge? Anyway...

Make sure your meter is on AC. Take the reading.

AC volts one coil x 1.4 = DCpeak volts one coil

DCpeak x number of coils per phase = DCpeakforphase

DCpeakforphase x 1.7 = DCpeakfor3phaseSTAR

Flux · « **Reply #8 on:** July 13, 2009, 10:57:34 AM »

I really haven't a clue what is going on. You still don't give any details to work from.

We have deduced that you have 16 magnets and 12 coils in the proposed winding. I assume this one test coil is the dimensions of one of the expected final coils. You don't say if you have one magnet rotor or two and no idea of the air gap if it is dual rotor. I assume the magnets are as specified for the 17ft machine.

As far as I can remember it is intended to be wound with about 60 turns for a 48v machine and 85rpm seems a reasonable cut in speed for 17ft.

If this is correct then the cut in speed at 48v with 60 turns will be 85rpm.

The voltage is directly proportional to the number of turns so your 236 turns should give you near 200v.

The number of turns is decided by how many times a wire is wound round, it doesn't matter how many strands in hand there are and within reason it doesn't matter much on wire size.

If you actually have 236 turns and only get 4v you must have much less flux than the intended machine, either you only have one magnet rotor, you have the air gap miles wide or the magnets are weak. The other possibility is an error in your voltmeter or tacho. At 85 rpm you can easily check by increasing it to 90 rpm and counting the turns.

Your formula should include root 3 where you have 3.

As I said previously 4 volts per coil gives 16v for 4 coils ( one phase). The line voltage when star connected will be x 1.73 ( root 3). The mean ac when rectified will be x 1.4.

Taking your 4 v per coil you should have 4 x 4 x 1.73 x 1.4 which gives your 38.7v which you seem to have got by luck with the wrong formula.

This is nearly a factor of 5 lower than what you should get from 236 turns per coil.

Until you sort out the errors there is no point in using more than one strand of wire. Just wind 60 turns of your wire on the intended coil winder former and you should get a figure that more or less matches the normal 48v machine.

Assuming the 85rpm cut in is correct then the volts per coil should be 48/( 4 x 1.73 a 1.4 ) which is very close to 5v. When you get this then wind 235 and you should get near 200v.

Unless you are trying for a high voltage machine I can't understand what you are messing with more turns for anyway, keep things to the book until you understand what you are doing.

Flux

Kid · « **Reply #9 on:** July 13, 2009, 10:12:26 PM »

I have dual rotors with about a 1" gap between the 2. The coil is close to the size I will end up with. I will try another one of my other meters to make sure that it is not the problem and check my air gap although the coil was almost rubbing when I did my test. Originally I had it wound for a 48v system with 14 ga wire and my readings were just fine but I was using a different meter.

Yes I am looking at building a high voltage system and I do agree to just using what is proven but I like to experiment a little. I build electrical panels and automated equipment for a living but find that this wind generator stuff is a little challenging if you never have done it. Well at least it helps stimulate the mind by studding something different.

I will double check my work tomorrow, until then thanks for the help.

"If you need a machine and don't buy it, then you will ultimately find you have paid for it but don't have it" - Henry Ford.

Flux · « **Reply #10 on:** July 14, 2009, 01:48:13 AM »

If the original coil worked then it must be your meter. The voltage should be directly proportional to the number of turns and really you don't need any more tests. If you double the number of turns you double the volts and it is just a case of using the correct size wire to get the maximum copper in with your chosen turns.

The air gap is the distance between magnets, the clearance between coil and magnets doesn't affect the voltage it just determines the thickest wire you can get in.

Meters are not expected to be used on low frequencies and waveforms that are far removed from sine waves, some work over a wide range but others are way off if you depart far from 50/60hz. See if the original meter makes sense.

Flux

Kid · « **Reply #11 on:** July 14, 2009, 11:39:12 AM »

Ok the other meter did the trick. I am getting 19v at 85rpm and 22v at 100rpm and I was spinning it by hand and holding the Tachometer in the other.

So using your formulas 19v x 4 x 1.73 x 1.4 = 184v @ 85rpm and 22v x 4 x 1.73 x 1.4 = 213v @ 100rpm that's more like it I will probably be adding some additional windings to get the voltage a little higher.

Don't know if I am wasting my time and going to the class of hard Knox; but the next step of investigation is to look into a grid tie only inverter and I was told that virtually all grid-tie small turbines are wound for 200 to 400 VDC. Well with my vary little experience in wind generated electricity I have not convinced my self nor have I been convinced that this will even work so before spending the money I must ask has any one been successful with a high voltage grid tie only wind turbine with furling and fixed pitch blades.

"Ambition is the path to success.

Persistence is the Vehicle you arrive in"

(William Eardley IV)

Flux · « **Reply #12 on:** July 14, 2009, 12:23:09 PM »

I am glad you sorted the voltage thing out, not all cheap meters are to be trusted when off frequency.

I am not sure what grid tie inverters are readily available but typically the 110v ones will need about 100v plus in and 240v ones will need 200v plus.

The main problem is the inverter maximum voltage limit. This is no problem with pitch control but simple turbines can easily go over the maximum inverter voltage before it has time to synchronise and they will be certain to do so if you loose load in a high wind.

The scheme works fine and these inverters all have some degree of tracking ability so they give more power than a simple battery charger.

Success or failure depends on your ability to limit the peak voltage, the circuitry is just about as complicated as the inverter, there are commercial devices and that is your best option unless you really know something about electronics. I believe that SMA now have something to protect the Windyboy inverter and any other serious inverter manufacturers should be able to offer something similar, if not you need something from an independent supplier or look for another inverter. Either way the solution will be expensive in the short term but you avoid years of continuous battery costs so in a good wind area it should pay off. Not a play project in a poor wind area.

Flux

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