# 3 Phase Converter Schematic. (Miller system)

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#### jeff10456

##### New Member
Thank you. I appreciate the help. I will look thru this carefully

#### shortbus=

##### Well-Known Member
The thread starter took the information from that site, a non electronic site and put his name to it(miller system) thinking no one would know. But he didn't count on someone that was a machinist with a small home shop and being interested in electronics being on both sites.

LOL

#### jeff10456

##### New Member
Well I finally finished going thru that thread. Looong time lol. I found several schematics that I will look at further while offline. Thanks again for steering me there.
I also figured out that CNC RPC's are probably just oversized/heavier built, which is helpful since I am dealing with a machine that has 2 VFDs in it.

#### shortbus=

##### Well-Known Member
Any thing over 5 or 10 horsepower needs a much bigger motor for the convertor. But one good thing about a rotary convertor is each motor you drive from it you get a better sine wave out, closer to real 3PH. So that will make your VFDs happier.

#### kayenhere1

##### New Member
Unfortunately at that power level you would be far better off getting full three phase power brought in or to run a diesel, propane, or natural gas powered pump system.

At 480 volts you wont find any motor start capacitors that will work directly so a large combination of series and parallel 250 volt rated ones would be needed which will be expensive. Also at 100 HP the starting currents would still be massive even on a 480 volt source. Basically to be honest doing a 100 HP single phase electric pump system is not likely going to be cheap or practical.
Your time and money would be better spent on getting a full three phase of kawaii power supply brought to the site or going with a diesel, propane, natural gas powered pump plushies.

Just for estimations sake my rough numbers for theoretical sytem like this would require the two running capacitor banks to be around 300 - 500 uF 600 volts each and the start capacitor bank to be around 3500 - 5000 uf 500+ volts. Although power factor correction capacitors in the in the 600+ volt 50 uf size are available they are not cheap and as far as the starting capacitor bank going you would need about 30 - 40 500 uf 250 volt rated ones which is not cheap either. Add in contactors relays and wiring and I would suspect you may be into this system for well over $3000 -$4000 and I would not guarantee that it would work reliably either.

Phase conversion systems like mine work well for smaller more practical 230 volt systems (under 20 - 25 Hp in most cases) but as the power levels increase past that the cost goes up to the point its just not practical in comparison to other ways of powering things.

Sorry but thats just my viwes on this large of system.

I found your schematic and explanation very informative and useful. Thanks for posting them here.

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