In article ,
Old Nick wrote:
On 26 Aug 2004 16:31:22 -0400, (DoN. Nichols)
vaguely proposed a theory
......and in reply I say!:
remove ns from my header address to reply via email
Now you see, _this_ is where the idea of a normal old 1 PH motor or 2
driving an alternator start to kick in again....G?)
So. I have a 20HP motor...3PH. If I ran it up to speed, using a pony,
I can then expect 80 amps, until I get it tuned? I just don't HAVE 80
Amps.
Hmm ... you could start out by adding a respectable capacitance
(power factor correction) in parallel with the motor to reduce that
current quite a bit so you could then tune the converter, and then tune
the power factor correction capacitance for the optimum current draw.
Note that the optimum will shift somewhat depending on load applied, so
if you expect to have the idler running unloaded more than at a
respectable load, you probably should tune the power factor correction
capacitance for the no-load condition.
Apparently running these things unbalanced is a lot messier than
running them on the right no of phases.
I'm not sure about that as far as the power factor correction
bit is concerned. It is just that if you have the right number of
phases available, you also typically have beefier breakers and wiring
available to start with.
Also -- I *think* (but I don't know for sure) that a fully
loaded motor would have much less need for the power factor correction.
Once tuned, what current would it use? How much more would it use than
say, a 10HP 3PH as an idler, in and of itself (not under load).
With both tuned, of course the 20 HP one would draw more
current. However a tuned (and power factor corrected) 20 HP motor
running as an unloaded idler probably will draw significantly less than
an unloaded 10 HP one running as an idler with no tuning or power factor
correction. You have a clamp-on ammeter don't you? Check what the 10
HP is currently drawing (I believe that you already have that one).
I don't have anything that big to check, since I actually use
VFDs, and lucked into my first one before ever building the planned
rotary converter -- or even acquiring the motor to serve as the idler.
Good Luck,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |
http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---