Hi all, I'm a relative newbie to this forum and looking for some help.
I recently purchased an older Fadal VMC 3016, wired 3 Phase. I've looked all over for the transformer to convert it to single phase, but have come up empty or looking at $3000+ pricetag.
I then turned my attention to an RPC to run this and any other machine I may find. I found a reasonably priced 30HP motor in great condition and have studied different solutions, but few go into details I can understand or to match the size of this motor.
One of the latest concerns I've had is the inrush of current to start this beast and whether my load center will support it. I have been toying with using a VFD to start up the idler, then switch to my single phase power with the created wild leg.
If anyone can help with this idea or other options, it would be greatly appreciated.
Starting load and its serious challenges aside for a moment..
"scale" the Fitch Williams RPC design at 3 times the capacitor values.
He publjshed his circuit right AT 10 HP to make that part easy.
Now.. slow-ramping the UNLOADED 30 HP idler up with a MUCH less-powerful VFD works fine ..for that PART...
What would be missing is any sychronization better than a dice-roll to the split-phase upstream feed's phase at the time you seek to cut it over.
That could get.."dramatic"
And then . VFD have some clever features, not all of which are always put to work. Taking input from a local shaft resolver or a remote data link is on that menu.
It "should be" possible, in a like manner, to "inform" the VFD that there is an external (to itself) phase you wish it to match its own phasing and load motor TO?
Ergo "somebody" has already done this. "Grid Tie" inverters do it, too.
"Your mission...." etc. or that of we chik'ns? .. is to find that info .. and see if the method can be applied.
Worth the research, IMNSHO.
You are not even CLOSE to the
only Seeker who would LOVE to have a better way to spin-up large idlers on barely adequate power.. that CAN easily haul the actual loads.. if but gotten up and running without a borderline major war, each attempt.
Getting this to work could be a LOT more "user friendly" than trying to "pony" an idler up ... and using a "synchroscope", manually. and "each go" . .ELSE risking the "drama."
The OTHER way to manage the inrush to a 30 HP idler is not to have it as so bad to begin with.
Start a 10 HP or 15 HP idler. Pause. Add another idler. Then again.
By four, if not three, or maybe just TWO?... the array of idlers is at your target 30 HP.. but it never hit the line for more than a portion of the inrush at any given point in time.
Works for me .. and even AT the 30 HP target.. if I'd but replace my 3 HP with a 5 HP.
10+3+7.5+7.5 = 28
Would become:
10+5+7.5+7.5 = 30
Downside is that is a lot of motors as idlers. And it was a lot of FREIGHT cost to get them HERE.
Upside .. and my primary reason to BOTHER -- is that I can tailor the idler HP actually on line to a wide range of loads. And put more online to START heavy loads than they will need to RUN in real-world loading... thus drop OFF some, if not MOST.. idler power once they ARE past THEIR starting inrush.
A modest VFD would have been CHEAPER, and not need as much SPACE, contactors, circuit breakers, capacitors, Weigemann boxes, wire, transformers and control switches.. so.
"Go for it!"
Manually . .with a synchroscope for openers. Those CAN be really SIMPLE. Blinkinwinkinlight simple.
It was how we paralleled-up multi-megawatt Diesel Gen sets "back in the....."
"Theatre of operations, NO commercial power.."... Vet-Nam War.
So the synchroscope part JF WORKS.
Now teaching a VFD... to do that sync... or a pig to whistle...