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Forum Index : Windmills : Stop Switch
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kenputer Newbie  Joined: 02/05/2006 Location: CanadaPosts: 30 |
Slowly getting my F&P up and running, what I would like some help on is setting up stop switch to short things out also weather to mount retifier at the gennie or at the batteries. Thanks Ken As good as you are and as bad as I am,I'm as good as you are as bad as I am! |
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| RossW Guru  Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Kill-switch is easy. A decent, high-current double-pole switch is all you need. Connect one side of both poles together and connect to one phase from the alternator. Connect the other side of each pole to the remaining two phases from the alternator. When the switch is open, all 3 phases are isolated from each other. When you close the switch (even though only two pole), you join all three phases together. Don't throw the switch when the thing is running at full speed though! As for the rectifier - I'd put it near the batteries. 1. It means you can put the kill switch near the batteries where it's convenient. 2. Running 3-phase down the mast reduces the current in the longest cable length, reducing losses. Cheers, RossW |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5019 |
Yeah I agree about putting the rectifier near the battery, even though I have mounted mine at the top of the windmill. I did it that way because it meant I only needed to run two wires down the mast, and it also meant the rectifier was up in the cool breeze. But it limits your options. If the rectifier fails, you need to take down the mill to replace it. And I would like to play around with "Kicking" the windmill to get it started in light winds by sending an electrical pulse back up the windmill. This is not possible with the rectifier up there. Ross is right about not throwing the kill switch while the windmill is running flat out. It wont have any effect, other than overheating the windings and possibly burning something out. You need to short it out before it gets a chance to speed up. If it is running flat out, say in a storm, there is not much you can do but cross your fingers and hope it stays together. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| kenputer Newbie Joined: 02/05/2006 Location: CanadaPosts: 30 |
Thanks for the advise and I will be putting the rectifier down near the batteries. I will have a run of less then 50' from gennie to retifier so will # 10 wire be large enough?,and then I have some large welding cable to use from rectifier to batteries. Thanks again Ken As good as you are and as bad as I am,I'm as good as you are as bad as I am! |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
It's all a balancing equation. Its not that 'x' size cable will be ok, and one size down will instantly burn out. Sure, thin hookup wire would probably melt... but assuming it's a "reasonable" cable, it comes down to your losses. In a house, a standard power circuit is wired with 2.5 square millimeter cable. That's good for at LEAST 10 amps, and usually has a 16A or 20A circuit breaker on it at the switchboard. A lot of houses only have one or two power circuits... and the wire loops from powerpoint to powerpoint. A lot more than 50m in total, I'd guess. Given you have 3-phase from the F&P, the current will be less per conductor for a given power than with a single phase circuit. So even if you have only 2.5 sq mm cable for 50m, it will certainly handle your 20 amps. Question is: at what price. Length in metres x current in amps x 0.017/conductor size in sq mm = voltage drop. (assuming DC, but it'll give us an idea for RMS/AC) 50m x 20A x .017/2.5mm = 6.8V. On a 12V system, you'd need at least 19V from the generator to get 12V at the battery, and WORSE is that you are *WASTING* 6.8V*20A = 136 watts heating up the cable. 50m x 20A x .017/4mm = 4.25V, so somewhat better. If you ran (lets be silly for a moment) 35mm welding cable, you'd have just under half a volt wasted, and under 10 watts lost in the cable! |
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