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Forum Index : Windmills : BRUSH LOSSES
| Author | Message | ||||
| FandPwithPVC Regular Member  Joined: 09/09/2006 Location: Posts: 64 |
HI ALL We have a test bench and two side by side windmills which which are meant to be the same except for the bits being tested. In putting up one of the F and P mills we smashed a brush assembly. So we built another which was still 3 brushes but made differently.It was decided to test one against the other using 24 volts and two 12 volt head light bulbs as a load . There was a voltage drop in each set and a big variation between the two assemblies which we had not looked at before. The automotive brushes were the best but far from 100%. It is probable the copper content of them makes them more suited. The newer set can be best described as a bit of a failure. MY QUESTION is about using no brushes at all and running 3 wires down the inside of the tower.We tried it some time back and it worked but we were put off by people who said it would cause problems. Has anyone done this and how well is it working. Brush assemblies are not the easiest to build and then find they cause losses. Thank you in anticipation of your reply and kind regards Dennis L |
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sPuDd Senior Member  Joined: 10/07/2007 Location: AustraliaPosts: 251 |
Pictures, specs, diagrams, measurements...? I have two cars and one of them always goes faster. sPuDd.. It should work ...in theory |
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| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hi Dennis,, Yes, I went to big trouble machining and making a nice brush holder assembly .. Even doubled up on the brushes (6) to decrease the resistance.. It didn't work -mechanically it was perfect- I even used braided wire ,heavy duty, did everything to lower the loss.. still some Ohms resistance ,,if I remember correctly. I've managed to get some chunky big brushes,,maybe one day I'll try again,,,or go to the spring brass slip ring contacts,,maybe this willwork.. As for the alternative,,,I've now got a 2 metre length of heavy duty 3 core (like welding cable) and use this from the hub to under the rotating hub ,,It works well,,hardly ever have to "un-twist" it ,,and mine is only 2 Metres long ,,others run this sort of cable all the way down the tower.. Sure,,u can see where it has twisted,,but it seems to make no difference,,and,,,,importantly,,no added resistance ,,like the brush set.. Hope you're keeping well,, Bruce Bushboy |
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| windlight Guru Joined: 03/03/2007 Location: AustraliaPosts: 331 |
I use drop cables down the tower centre and never unwind them. The secret to this is no turbulance, if you have trees nearby they will cause it to wind up. My origional mill would wind up badly, longest between unwinding was a week, removed one more tree and never unwound it again. allan "I like this place and willingly could waste my time in it" - (Act II, Scene IV). |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Hi Dennis, We have dumped the slip rings in the 3.6m AWP over here. Best thing we ever did.... and this one is High Voltage. (200-300volts) This means that resistance in the brushes was not the issue, (only 4-5amps), just the carbon glazing, ring wear, and just another place to fail. If the head moves vertically, then it damages the ring/brush alignment... sometimes badly. Now an unwind about once every 2 months, ... if it needs it or not. Mostly not really. If it were a low voltage high current machine, then slip rings would not even be considered. The bigger machines over here have no slip rings either. Unless you are a brave person with an unmanned for prolonged periods mill, or in a turbulent area (because you have no choice) then slip rings find it difficult to justify their existence. .........oztules Village idiot...or... just another hack out of his depth |
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sodes Newbie  Joined: 26/07/2006 Location: AustraliaPosts: 21 |
Hi all, I dont mean to butt in Dennis, but Bruce im very interested in your setup with ya welding cable. Im just building my first f&p gen now and wondering if you could share your details on that cable setup mate? Cheers Sodes "Do, or do not... There is no try." -Yoda |
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| sPuDd Senior Member Joined: 10/07/2007 Location: AustraliaPosts: 251 |
Liquid Metal Slip Rings - Mercotac These guys have distributors in just about every country. Don't know what the price is, but I'll be using them on my 1Kw conversion soon. I figure pay the $$$ and never have to deal with twist again. sPuDd.. It should work ...in theory |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi sPuDd, The mercury wetted devices you mention above would work well. The units have maximum current ratings of 30A per terminal. A 3 terminal 30A unit will set you back at least AU$300.00 . For higher current you would need more terminals. A 60A version is over AU$1000.00 . I am not sure if my budget could go that far. Gordon. become more energy aware |
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| sPuDd Senior Member Joined: 10/07/2007 Location: AustraliaPosts: 251 |
G'day Gordon, On the surface they seem expensive, but as an important part of a highly reliable system they are well worth it. For me at 48V the 30amp units are viable, but using them on 12V systems could be expensive. I suppose like any large purchase, one must weigh up the initial cost Vs reliability and decide what is most appropriate. From a technical perspective, they appear to leave brushes for dead. sPuDd.. It should work ...in theory |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hello,, Sodes,, This is the Cortina hub that I fitted the copper rings to --sort of 6mm "wedding" rings from copper water pipe with the cable soldered inside.. The brush holder is somewhere in my store ,,but too many black snakes in there at present to find it. Actually the brush holders were just automotive generator or alternator holders,,retrofitted to alumimium angle ,,two brushes per ring --worked very well,,but the resistance is the killer,,at 12volts. Bruce 
Bushboy |
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