A quick general note regarding regulation. It is my experience that in smaller systems regulation is best done at the electrical output end rather then water intake end. A power diverter using IGBT or TRIAC power elements, or even relays, is by far the cheapest and most reliable way to govern the output of < 5 kilowatt output systems. In the < 100 volt range these units are available off the shelf from many vendors, while the 120V and up systems are more costly and somewhat harder to to source. At the end of the day they are still a better investment if only for the reason that you might still want one even with a water flow diverter installed, in case the valve sticks open.
Rob Quoting tom kasmer <[EMAIL PROTECTED]>: > > > > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Does your company feature in the microhydro business directory at > http://microhydropower.net/directory ? 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