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Forum Index : Electronics : Crazy idea
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Ken. Newbie  Joined: 05/10/2008 Location: AustraliaPosts: 13 |
Hi guys, I had a bright idea that I'm hoping you guys can shoot down in flames.  We are talking theoretical at this stage.... We all know that field windings use power...Perm motors have cogging problems.
What about a marriage between the two? If I was to use a Delco Remy Alt as my main Generator (regulator removed). (big Vawt to push it and the gearing) and I used a small perm motor whose cogging effects wouldn't be felt by such a big turbine. The perm motors job is to supply power to the windings on the delco remy. That way the power produced by the alt' increases slowly until a good speed is atained. The speed the perm spins dictates how much power it produces to the field windings in the delco which in turn dictates how much drag is on the turbine at low wind speeds. So there you have it...genius!
Feel free to be brutal guys  It's just an idea that might let me use my favorite alt' (Awesome for hydros')
Has anyone ever put magnets in one of them?...I often wondered how that would go. "Imagination is greater than knowledge" Albert Einstien |
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Gill Senior Member  Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Ken, There seems to be some clever thinking in there. I am not a supporter of gearing so shudder at the thought of driving two generators, yet your system loads accordingly so for one who's heart is set on that Delco Remy perhaps this is the way. Remember we want a few good pics and the story to inspire us as you build.  was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
The output voltage of the small exciter generator will increase proportional to rpm. The wound stator will require higher current at low rpm, and as the rpm increases, the current can be reduced. The system you propose will not provide the required relationship without some external regulator. It may be simpler to just use an rpm sensor and engage the stator coils above a set point with current from the battery, controlled by an output regulator system. This would save a lot of mechanicals. Gordon. become more energy aware |
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| Ken. Newbie Joined: 05/10/2008 Location: AustraliaPosts: 13 |
Hi Gill, thanks for the encouragement. I wouldn't say my heart was set on a Delco as such but I do love the way they are put together! They are a "set and forget" alt' with sealed bearings and no brushes. A work of art really. Perfect for harsh environments EG: down in a rainforest creek just humming away for years. Short of some major rewinding or building an alt' from scratch (not my first choice, must be a nightmare) I can't see any way around the gearing issue. Exept make it a BIG vawt to handle the extra drag of the gearing. I have the go-ahead from a mate who I'm building this for (as long as it doesn't cost TOO much) He's a smart guy but electricaly challenged mostly due to apathy in this area. This thing HAS to be reliable and be "set and forget". It will have to eventually hook up to a grid feed solar system I'm helping him organise. I've allways wanted to build one of these things ( H wing vawt) and now someone else is willing to pick up the tab! Busy or not I'm sorely tempted.  There may be a whole HEAP of dumb questions to follow if I decide to start this project...I appologise in advance and promise a full running report (with pics) on progress. "Imagination is greater than knowledge" Albert Einstien |
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| Ken. Newbie Joined: 05/10/2008 Location: AustraliaPosts: 13 |
GWatPE, well spotted! you are quite right..Thanks for that. One option I was considering was using a voltage sensor on the perm output to switch the field windings on when there is sufficient power to run them but I was concerned about how to keep the drag gradualy climbing. I imagine you'd end up starting "hystersis" when the field windings cut in the rpm would drop cutting the power. ( unless I used a different cut-in voltage than cut-out) The possibilities are endless! This may have me scratching my head for a while yet..Thanks again  "Imagination is greater than knowledge" Albert Einstien |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Ken, that is pretty much how the generator is excited on my larger windmill. The main generator in the windmill is an old slipring motor, that is converted to work like a car alternator; supply dc to the field windings and it will generate 3-phase AC. The excitation current for the field is generated with a car alternator, which has the regulator removed, and replaced with direct feed brushes for the rotor. The output on the main generator can then be controlled by varying the small excitation current on the aux. alternator. The best part in this is that the output of the generator is easily controlled, and good power tracking curve can be obtained. The bad part is, that field extitation requires power, and hits the low wind efficiency. Janne If at first you don't succeed, try again. My projects |
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