1.  2- 10 mf capacitors in parallel = 20 mf. ?
   2. 2- 10 mf in series = 5 mf?
   3. can 2- 100 volt rated caps placed in series handle 200 volts?

That is correct.

Cheers.

TomW

got anymore info on induction generators? i could use a bit more info on connections and how much capacitors to use

Once you are done I believe you will find that an IMAG (induction motor as generator) is a poor substitute for a real generator. The frequency will fluctuate with RPM and the voltage will fluctuate with load which will require capacitor value changes to bring the voltage back in line with the load. In addition to which if the load swings too much the motor will just plain quit generating.

On the caps you are correct.

as for using the motor as a generator, i realize there are limitations. There is no active voltage regulation, and additional caps may have to be incorporated to correct for loading. frequency is another issue, but as i understand it is more a function of driven rpm and thusly the ability for the prime mover to hold the rpm constant over the design load rating. Am i correct so far?

the motor i am using is a 230/460 15 hp unit.

the most it will ever see at anyone time is approx a total of 1 hp of induction motor, the balance will be resistive loads ie. lighting

this unit is incorporated into the cogenerator scheme, and will only be used to run the washer/dryer while in the run mode, which is targeted to be no more than two runs of 2 hours per day maximum

cost is also a factor as i picked up the motor for 75 bucks including a 42/gallon per min at 1000 psi hyd pump, with love joy and all mounting hardware. as you see i have little investment in the motor, and i think an over capacity for what i plan on actually pulling off of it, so voltage regulation should not be as large a problem as with a smaller (lower hp) induction motor to generator conversion.

does this make sense? does to me

still looking for capacitor values, anyone else have any links or ideas?

found a couple of good sites last night, getting more and more info on power factor correction and switching schemes to correct voltage under load.

i think i am getting closer, bought ready to order some run caps and build up the cap bank.

2. The frequency might not stay exactly 60 hrz.
3. I pull off one leg to run the washing machine. it does fine.
4. Sometimes if the caps sit too long it won't start under load.
5. With generator spinning, arc a battery across the caps, to start when dead.

thanks for the input, a couple of questions

1. the redrock schematic, where do i find it?
2. where are you connecting the 220 vac 50 mfd caps? it is my understanding that i need at least 480 vac units.. perhaps the schematic i have has them connected differently than you do on yours.
3. can i get a copy of you schematic to compare to the one i am using?

the predominant use would be washer/dryer motors, refridgeration compressor, and light loads while the cogenerator is running.

so far i have the control panel completed, it is basically a relay system to auto switch from inverters to the induction generator while the cogenerator is running.

if you can add more help or ideas i would appreciate it, as well if i can get to use 370 vac caps or less i am all the more ahead as i can get them cheap from surplus center in nebraska.

thanks for your help

http://www.redrok.com/cimtext.pdf

thank you for the effort

i like your genset, looks good

i looked up the redrock site and found two differing shematics, one is wye and one is delta.

which did you use?

I am a registered electrical engineer, and happen to be setting up a home cogen setup much like the ones you folks are describing.  I have some serious concerns about that pdf file you are referencing, with the myriad connections in different places for caps and 120V feeds.

First of all, the setup as indicated is wired for the standard high voltage configuration, likely 480V configuration.  This necessitates that you install higher voltage, mor expensive caps than necessary.  I don't see why the author thinks they need to be placed on the high voltage legs in the first place.

Secondly, and more importantly, the configuration shown is not only extremely confusing, it is providing only half the rated capacity of the motor/generator if you are set up to take off 208Y/120V which is what most people are doing (whether they know it or not :-))

Mosst of the rest of what is written in that article however is pretty accurate, but that schematic is confusing enough that it may get somebody killed, thus I thought this note was in order.

Those windings within a typical motor are much like a center-tapped transformer, and are meant to be series wired for the higher voltage and parallel wired for the lower voltage.  This is why the wires are taken to the outside of the case for field arrangement in the first place.  Tapping only the midpoint of the series arrangement, will only give you half the current capacity of the motor's rating.  The other (3) coils are just sitting there in series with the caps making reactive (unusable) current. Unless I misunderstood the circuit, which I doubt.

Regarding capacitor selection, don't look for some reference book to tell you what you need, this needs to be selected in the field due to rpm, inherent inductive value, hp and other factors.  It is quite simple, just get your rpm regulation in order, set the system up with some caps just enough to make some voltage (by trial and error) and adjust your rpm to get as close to 60 Hertz as possible.   Obviously the rpm has an operating window and will fluctuate a little but if its swing is minimized, it won't affect anything except line powered motor type clocks, which almost nobody has nowadays anyhow.

Then, adjust your no-load voltage by adding or subtracting caps.  Get your no load voltage at the high end of tolerance, say 130V line to neutral.  Then as you add load, the voltage will droop some, but if your system is large enough, it will still be within acceptable limits.  I would avoid drooping below about 105V though.

Reactive loads such as motors are going to cause the most droop during continuous running, and you can fix this too.  Add the correct value of motor run (power factor correction caps) directly to the large motor's leads, so that the cap is only connected when the motor is powered.  This is standard industrial practice and there are charts available which tell you exactly what size to use (unlike for motors-as- generator cap selection).  Then your big motors won't cause such a droop.

Again, most of what others say in this thread is correct.  Wire in series same value caps will halve the mfd value and double the voltage rating.  Parallel will double the mfd rating with keeping the same voltage rating.  Don't undersize the voltage rating unless you want fireworks and oil sprayed all over the place.

Another note, what you are looking for is nominal 208V line to line measurement.  That is standard 3-phase voltage, which gets you the 120V rating.  Of course you will be varying the voltage as previously discussed, but many people confuse 240V with 208V systems, and think that they are going for 240V, and wonder why the single phase voltage is up to 138V or more.  The reason is that sq.root of 3 times 120V gives you the necessary line to line voltage for three phase systems.

One other note.  You don't HAVE to take off all 3 phases.  You can just put one bank of caps across 2 lines, use those 2 lines plus your center tapped neutral (GROUND IT for SAFETY) and have a nice 208V single phase system with 120V available from either leg to neutral also.  So remember, your caps go from line-to-line, not line-to-neutral.

Regarding startup, you are not supposed to start up ANY generator under load in the first place, so if you follow that rule, you should nearly never have a problem unless you run out of gas or something and possibly lose the residual magnetism for that reason.  12VDC across the lines for a second or 2 will fix that in a hurry.  You could even automate that with some contactor arrangement to spark the windings during initial startup to be sure :-)
Hope all this helps,