otherpower type turbine

[gordon01639]

Finally got started on my windturbine page on my site the url is

http://www.segmentedturning.co.uk/windturbine.html

got started on the testing today.full report to follow.

please comment here though not in my guest book, although you could say something nice about my turning in my guest book if you like.

Gordon

Wales in the UK.

[Flux]

I don't like the idea of having to read this on one site and comment here so that your site looks pretty.

You are a little unfair on British magnet suppliers, they are more expensive but £4.25

is about typical in that quantity, not £10.

Flux

[gordon01639]

I haven't been able to find any supplier over here that sells them in quantity, do you know of a supplier that does? please let me know. as £108 would not be so bad.

Gordon.

Wales in the UK.

[Flux]

Powermagnetstore is that price for greater than 20 of the metric version 48 x 30 x 10mm, which I find to be the better option. I think their price is a little higher for the imperial size unless you buy 100.

John Miller has some on his site Otherpower. co.uk but again I think they are metric and although he claims to be cheaper there is little in it.

With your 10" discs the imperial ones would be better, but on 12" discs the metrics seem to be a good choice, and would better suit the thin stator you seem to have adopted. Did you mention the number of turns, I couldn't find it or system voltage.

Nice looking blades and lathe work.

Flux

[gordon01639]

flux.

Thanks for the info I will look into it at least if I buy them in the UK I wont have to worry so much about them getting lost on the way. The system is for 12 volts 42 windings of 17 swg 2 in the hand. I have done a little testing and cut in seems to be around 118 rpm for charging. I will update the other page later, cooking the dinner at the moment.

Also I have changed my mind about my guestbook if you want please do use it.I just thought it might be better to have it here as it is easier and keeps it all together.

Gordon.

Wales in the UK

[Flux]

That cut in is dreadfully slow, I think you will end up delta connecting it to get it out of stall. It will let you get more out of the thin wire, but you will have to put up with circulating currents.

Flux

[gordon01639]

Flux,

I did try delta connecting it and got cut in at about 140 rpm to charge a battery, I have read an awful lot on this site and the speed that most people tend to aim for is 120 rpm for cut in. although we do usually get wind most of the time it tends to be in the 10 to 20 mph range, do you think I should change it for delta? this is the first windturbine I have made so everything I do is a new experience for me and any advice will be gratefully recieved, negative or positive. I was a bit worried that the voltage when star connected went very high well up into the 30's at about 350 rpm (blew a few bulbs) even when connected to the battery. I thought that the voltage would remain at what the battery voltage was or 2 or 3 volts higher. I dont want to damage my batteries.

Gordon.

[Flux]

I can understand why the confusion, some people here are always reluctant to give full information and it does lead to the wrong conclusions sometimes.

Cut in speed needs to be related to prop diameter and to tsr. Most of the props here are typically of tsr6 or 7 so the main confusion is the cut in speed compared with prop diameter.

At cut in the average prop will reasonably happily run up to tsr 8 so if we think of your case with an 8ft prop ( just over I think) for 7mph cut in you have 7 x 88/60 ft sec = 10.2ft/sec wind speed. Tip speed will be 8 x 10.2 = 81.6 ft sec.

prop circumference is 8 x pi ft = 25.12ft.

Revs/sec =81.6/25.12 = 3.25 rps or 195 rpm.

Yes many here do talk about cut in speeds of 120 rpm but that would be for about a 14ft prop at the same tsr.

Even 140 that you got in delta is a bit on the slow side and you would be wise to increase the air gap to raise it to over 170 rpm. There is no useful power in winds below 7mph and lower cut in speeds will cost you dearly in output in the 12 mph and upwards band.

Don't worry about the voltage, the battery will clamp the voltage until fully charged, then you will need some form of charge control unless you are prepared to control load manually ( not really practical) unless you are there all the time.

Ignore the voltage issue until the batteries are near full charge then try to maintain about 14v. Without some form of charge controller you will get up to about 17v in high winds and if maintained that will use lots of water and cause rapid battery damage. You can't overcome this issue by messing with cut in speed.

flux

[gordon01639]

Flux,

Thanks for the advice I will alter the air gap and see what I get, at the moment the gap is only about 7/16 inch this is a gap of 1/16 inch iether side of the stator, what do you think might be reasonable gap if I was to reconnect in delta. I can do this quite easily as I have all the wires connected to posts on the stator.

are you in the UK or America.

Gordon.

[Flux]

With those magnets I would have made the stator 1/2" thick and used about 30 turns with an air gap about 3/4". You would have had room for thicker wire.

Try your gap at about 5/8". You will manage with that size wire connected delta if you are careful with an 8ft prop. Try to keep your furling to fairly low winds but you should be ok for short bursts up to about 30A, but don't push that thin wire too hard.

You may be safer to keep cut in a bit lower than ideal to keep things stalled a bit in higher winds to make control easier. Try cut in at 160 for a start but normally over 170 would do better.

I am in the uk.

flux

[gordon01639]

Flux,

Hi again, I have altered the gap this morning to about 5/8 I get cut in at 150 rpm with star configuration and cut in at about 200 rpm in delta. I tried it with a load(12 volt 50 watt halogen) as well as the battery, and in delta I couldn't spin it fast enough to get over 7 volts (turning by hand) but in star I could still get cut in at about 200 rpm.

When you talk about stalling do you mean the point at which the force from the flux on the coils gets to a stage where it is to great to speed up anymore? not really found anything much about stalling on this board. I should think it is probably current related.

I'm not sure whether you noticed that I used 2 17 swg in hand or not, so I actually have over 2mm of copper.

You have really been a great help to me, Thank you very much.

Where are you in the UK?

Gordon.

[Flux]

Some of this data is conflicting, I am not sure what you are calling cut in speed.

It is the speed at which it just starts to charge a 12v battery. If you are measuring open circuit dc volts then it will be when you reach about 12v dc. If you have an ammeter it will be when you start to see current into a battery.

If you are measuring things into lamps then you are confusing things.

If you have a cut in of 150 rpm in star, then in delta it should be over 250 rpm in delta, that is why I question your figures. Let's be sure you are measuring the right thing before doing too much worrying about air gaps.

Stall refers to the effect on the blades when you hold them below their ideal speed, it has to do with aerodynamics and nothing at all to do with electrical things.

You are new here and this has been covered many times, but it is sometimes difficult to find what you want without going through many pages of slightly related but not the same data.

At some time in the past I did a diary entry on matching the load, see if you can find it, it will cover all the basics that you need.

Regarding wire size, 2 x 17 swg is fairly thin for a 12v winding. Typically with 12 magnet discs that winding would have about 33 turns per coil of about 2.5mm diameter wire ( 4.8mm squared csa)

Flux

[Flux]

Hope this link works

http://www.fieldlines.com/story/2006/3/17/185646/194

[gordon01639]

Flux,

Sorry I should have said that the 12 volt cut in for star at 150 rpm was into a battery as it was with delta at just over 200 rpm . The test with the lamp was a seperate test.

Been reading your diary entry for about 90 minutes now and I must say in all honesty that most of it just went right over my head. Although I did city and guilds electronics it was a long time ago, if you dont use it you lose it.

I am going to try it in star configuration and see what happens in the wind on a test pole, it's never quite the same spinning something by hand its hard to keep a constant speed. Thanks agin for your help. I will update you when I get some real world figures.

You never said where in the UK you are.

Gordon