Joe: One solution to protect from field collapse is to insert in the stator windings a set of magnets, one at each end of a winding pole ( close to the casing ends) and the opposite polarity at the 180 degrees half winding. ( four magnets per pole pair).
This way if the field collapses due to over loads, when the overload is removed ( ELC off) the magnets will make the rotor produce voltage to re-new the generator field -- we did this several decades ago when we started using Induction motors as generators --. Also, the system had voltage detectors as well as current to shut off certain loads for proper re-magnetizing under power hydro power The concept was tested several times in different generators and worked well every time. Regards Nando ----- Original Message ----- From: "Joseph Hartvigsen" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, December 19, 2005 4:22 PM Subject: [microhydro] Re: Alternator recommendations > Hi Eric, > I also use a 3 phase capacitor excited induction motor. Just be > carefull not to have too much load in the dump loads or the field > will collapse and lose excitation. I have a 3 hp motor, 1800 rpm > rated running at ~2300 rpm. When I put the 3 16 ohm loads in at first > I had them in wye on all 3 phases, but that didn't work and the > system would freewheel after loosing excitation. So I went to the 3 > 16 ohm loads in series across only two legs. This scheme should > actually work more reliably with a PM type alternator or a powered > field type alternator. > > More details of my system are at the following link (not updateded > for this new mod) http://h-hydro.com/Aspen_Hollow_Hydro.html > > Joe > > > --- In [email protected], [EMAIL PROTECTED] wrote: >> >> Hello, >> >> Very good description of your system. >> Very interristing for me in direct application ! >> Thanks a lot >> >> I've got the same system of your >> >> I don't use all the power i can use because of the dumps load who > are >> limited in power. The dump loads are standard 240V 3000W water >> heaters on a pressure tank.(3 phases 400V/240V standard electric > boiler) >> But y use them in 24V so only 300W is used. >> If i use them on the 240V line, i will dump 9000W (only 1300W are OK >> for me) >> I've got the solid state relays in stock ! and the resistors too ! >> (3 phases relays with 3-32V DC command( internal 40VDC protection) >> Carlo gavazzi or crouzet) >> >> So i will try this arrangement soon. >> My generator is an old induction motor used in generator with > capacitors. >> What is your ? >> >> Regards >> Eric >> >> >> ----Message d'origine---- >> >A: [email protected] >> >De: "Joseph Hartvigsen" <[EMAIL PROTECTED]> >> >Date: Fri, 16 Dec 2005 20:25:11 -0000 >> >Sujet: [microhydro] Re: Alternator recommendations >> > >> >I agree with Rob that for small systems it is much simpler and more >> >reliable to regulate the power rather than the water flow. Most of >> >these small systems will be used for battery charging, but the > power >> >may be delivered as AC at higher voltage. In such cases there is an >> >easy way to regulate the system by putting the dump load across > the AC >> >line rather than the DC. >> > >> >Rather than deal in general terms I'll explain how my recently >> >modified system is set up. >> > >> >Power comes from the turbine driven induction motor as 3 phase AC > at >> >about 167V. >> > >> >[A side note: It is at 167V because it then goes to 3 transformers >> >setup as 240V (delta) primaries and 32V wye/star secondaries then > to a >> >3 phase bridge rectifier with the output connected to a 48V (56V >> >typical) battery bank. Unlike single phase, where the RMS voltage > of >> >the rectified sinewave DC output is exactly the same as the RMS AC >> >input, in 3 phase the DC output voltage is 1.35 times the leg to > leg >> >AC voltage. So, the battery clamps the rectifier output to 48-56V >> >depending on state of charge, which means the AC phase to phase > input >> >is ~52/1.35 = 38.6Vac, which means each of the transformer > secondaries >> >forming the wye/star is 38.6/sqrt(3) = 22.3Vac, that means the >> >primaries are 240*22.3/32 = 167V. If I had used nominal 24V output >> >transformers in wye to the 3 phase bridge, the primaries would run >> >closer to the rated voltage. 24*1.35*sqrt(3) = 56.1V ] >> > >> >I used a solar charge controller, Morningstar TS-45 and configured > it >> >in diversion load mode with its inputs connected to the battery +/- >> >and outputs connected to two resistors in series. These resistors > can be >> >relatively low wattage, sized for only 30-50mA. For example with > 60V >> >peak battery equalization voltage, split across two resistors > 50mA*30V >> >= 1.5W and 30V/0.05A = 600ohm. So you could go with two standard >> >value 680 ohm or even 1k-ohm resistors rated at 5W or 10W > connected in >> >series and connected across the TS-45 load +/- terminals. Clearly > this >> >won't dissipate much power, but it does provide a 24-28Vdc signal >> >between the load (-) terminal and the point between the two > resistors >> >which I use to fire AC solid state relays (SSRs). If you have a 12 > or >> >24V battery bank you can fire the 3-32Vdc triggered type AC SSR >> >directly from the TS-45 output terminals. If you have higher than a >> >48V battery bank use more of the resistors in series and take the > SSR >> >trigger (+) signal from the opposite lead of the resistor > connected to >> >the (-) terminal. >> > >> >Now, whenever the battery bank voltage is at the control limit, the >> >TS-45 in trying to dump power actually just sends a signal to > trigger >> >the SSRs. The SSRs are connected to AC line voltage from the hydro > on >> >one side, and a load resistor on the other side. You can find these >> >relays rated to 25A (using a heat sink) at 240V for about $20 each > at >> >most electrical supply places. >> > >> >I had previously used some old oven and drier heating elements, but >> >they took up too much space on the wall. So I put three 300W 16ohm >> >edgewound and enamel coated resistors in series across the 167V > from >> >the hydro. That will dump in my case ~580W, but it is easy enough > to >> >size these resistors to dump what power you need at the generator > line >> >voltage. >> > >> >I purchased the resistors from digikey.com The 300W version are > $16.48 >> >each, part number FVE-300-xx (xx is resistance in ohms from 0.5, > 1.2, >> >2.0, 5.0, 8.0, 10, 12, 16, and 20). A larger 1000W resistor (black >> >silicone finish rather than enamel coated) is available for $51.50 >> >each, part number FSE1000-xxx (-.25, .50, 1.0, 3.5, 4.5, 10, 15). > Both >> >also have a mounting kit available. Of course if you have a > useful AC >> >load of appropriate power and voltage rating that can be connected > and >> >disconnected such as a water heater use it. >> > >> >So, in simple terms, the PV load controller senses battery voltage, >> >triggers SSRs which connect an the AC diversion load across the > lines >> >from the hydro. >> > >> > Joe >> > >> > http://h-hydro.com >> > >> > >> >--- In [email protected], [EMAIL PROTECTED] wrote: >> >> >> >> 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 ? 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! 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