Hi Craig
On (27 Aug 97) Craig Healy wrote to Alec Cameron...
 CH> Re: Cogeneration unit..
-> Ahah! And how do you achieve constant power? I guess you might clamp
-> throttle bar and have a speed limiter to protect your machine if the
-> dead on you [breaker or fuse opening at your end]
 CH> That would cause an overvoltage.  Could easily disconnect the ignition,
 CH> fuel and AC by means of relays.  Same with undervoltage.  Or, a
 CH> simple frequency comparitor could be made.  If the frequency seen is
 CH> more than a Hz off of 60Hz, then a shutdown occurs.  Lots of ways.
Nothing you do with an induction generator [ie a conventional AC motor, non-
synchronous] will cause overvoltage- unless you have added shunt capacitors,
which I would advise against.
Any overvoltage resulting from the trip of a synchronous generator, should be
followed by voltage regulator action. In which case the tripping of a voltage
relay, should be time delayed to give the AVR a chance to do its thing.
As you say, lots of ways. But it ain't easy to pick the right way first off.
Trial and error design,  may mean early retirement of some damaged hardware.
                                             
 CH> My initial thought was to use a generator designed to run from a tractor
 CH> PTO at 540 RPM.  That would be a synchronous generator, and regulated.
 CH> Probably closer to the "constant power" thought.
I assume 540 rpm is the engine speed not the generator speed. To generate
approx 60Hz at 540 rpm you would need a 12 pole induction motor or 
ynchronous
alternator. Not a common machine. Belt gear or chain drive to spin the
generator much faster than engine rpm, desirable.
 CH> That may well be so, but the area covered by the substation is quite
 CH> substantial, and I'm right off a main feeder.  One of those things you
 CH> can't tell for sure until you try.
Let's have your report when the champagne bottle is cracked!  Cheers....ALEC
... ....Horsepower was a wonderful thing when only horses had it
--- PPoint 1.92
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