Hi Bill
On (10 Dec 96) BILL BAUER wrote to Roy J. Tellason...
 BB> While it's not going to be free or particularly cheap nor all that
 BB> easy, I'm planning on building me a backup power system for my house.
 BB> I gonna use an older car engine and tranny that I can get for maybe
 BB> a couple of hundred bucks and a 10 horse induction motor that's 
 BB> rated at 220/440 volts single phase and use the car engine to turn
 BB> that. I don't know for sure how much power that will produce, but it
 BB> ought to be pretty hefty.
Good news, bad news. Your 10HP single phase induction motor will work OK as a
generator but ONLY while the grid is OK. Open the throttle on the engine and
see the meter spin backward. Great!
BUT when the grid drops [blackout, storm, whatever] you will find that your
engine driven 10 HP motor will go quite mad. No generation. Its terminal
voltage will collapse or at worst, oscillate all over and maybe damage your
lamps, refrigerator etc.
 I think it ought to produce maybe 30 KW
 BB> of power
I think I may have missed something here. A 10HP induction motor running as a
generator can hardly generate 30 KW.  As the windings would carry roughly 3
times rated current, the copper losses and the temperature rise, would be
roughly 10 times the proper value. Very hot and smelly.
 BB> ................................................... I'll have to
 BB> build a frame for the system and put it on wheels so it can be towed
 BB> if necessary and I'll also have to design and build a good regulator
 BB> for it and some means for it to detect when the grid power goes off
 BB> and make that trigger startup of the system. I'll also have to have
 BB> a system to regulate the speed of the engine so it produces 60 cycle
 BB> power and under varying load conditions. Then there will have to be
 BB> a system to pulse the motor windings with a D.C. voltage if it needs
 BB> a kick start to start it generating.
You are in for an exciting time. Get expert help! How will you hold the load
voltage at a reasonable value? Be prepared for wild oscillations in the range
zero to 50 percent excess voltage.
Induction motors driven by gas engines, were very common in Sydney NSW after
WW2. But these could ONLY generate while the grid was alive, the reason these
were used was because no generating capacity was added during WW2 and the 
oad
had grown. The large number of large induction motors driven by petrol
engines, helped reduce the district blackouts at that time.
Sorry I can't offer any solutions. But I feel certain, an induction motor
won't do the job. BUT if it is that rare beast, a synchronous motor having
sliprings and windings on the rotor....... then you can generate while the
grid is dead.   Cheers....ALEC
... ....The wheel is environmentally unviable
--- PPoint 1.92
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