using a PM motor as a generator has the following tenet. It has no regulation mechanism other than shaft speed, so here's what I suggest. You could rig up a smart bypass of the flow to regulate the speed so as to regulate the output power. Im sure that a magnetically coupled rotor excitation will indeed be expensive. Having a lot of experience in the fields of electricity and magnetism, unless this fancy generator has a few successful years of use in the field, I would stay away from it. You will have little or no recourse if it fails since is not in a car. Tom
--- williameverettstone <[EMAIL PROTECTED]> wrote: > Thanks for the reply. > > 50gpm is the minimum flow even in times of drought. > > Several formulas on the net showed we could expect > to produce about 20 > watts w/ 50gpm and 4-5' head. This equates to 1.6 > amps at 12 volts. I > figured 1-1.5 just to be realistic. > > Thanks for the advice on PM motors, I'll check them > out. Since posting > I found that Delco has come out with brushless > alternators available > in 12, 24 and 48 volts. I'm waiting for a quote on > one now, rewound to > produce at lower RPM. I expect it's going to be too > pricey. > > Thanks again. > > > > --- In [email protected], tom kasmer > <[EMAIL PROTECTED]> wrote: > > > > > > my experience witn GM alternators is that the > brushes > > will last > > about 150,000 miles + or -. That is a half year of > > steady driving. The alternator is subjected to > > underhood temperature extreemes and wild > > accelerations. In an outdoor enclosed housing, > > running at a fairly constant speed, you might get > a > > year of 24/7. > > Your 1-1.5 amps sounds low. How did you get that > > number? As far as PM generators, any PM motor will > > work nicely as a generator. > > 4 feet of head is only 2 psi of pressure. How much > > total flow > > does the creek have worst case drought time? Is > that > > the 50 gpm number? If you are limited to this > level of > > power, that is about > > 20 watts best case with an automotive generator. > You > > might better spend your budget on a photovoltaic > array > > and settle for > > daylight only solar power with less hassle. Im not > an > > expert in microhydro power so others may do > better. > > Tom Kasmer > > > > --- williameverettstone <[EMAIL PROTECTED]> wrote: > > > > > Hi All, > > > I have a situation with minimum 50gpm flow year > > > round (I have been > > > measuring for 5 years, through drought and > different > > > seasons). > > > > > > My wife and I are planning to rebuild the > remnants > > > of a small dam on > > > the creek which would provide about 4' head. We > > > estimate we could > > > generate 1 to 1.5 amps here. > > > > > > We are on a budget, and a prebuilt micro hydro > unit > > > is out of the > > > question, at least the ones I've seen so far > ($1,000 > > > and up). > > > > > > If we were to use an off the shelf auto/truck > > > alternator w/ brushes, > > > how long can we expect the brushes to last > running > > > 24/7? Are PM > > > alternators available, and how pricey are they? > > > > > > My second dilemma is predicting the best turbine > > > type and size, and > > > pulley ratio to obtain the highest RPM at the > > > alternator with the > > > available water flow. Is there a method to help > make > > > these decisions? > > > If we fabricate some sort of squirrel cage type > > > turbine, how do I > > > decide the optimum radius of the unit? > > > > > > Thanks so much for any help! > > > Bill > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
