Rotary phase converter

kuraki

kuraki

Fimbulvetr Knifeworks
Joined
Jun 17, 2016
Messages
4,679
Has anyone here built their own rotary converter? VFDs are great but I'm spread out enough now that using 1 to power multiple pieces isn't really viable, and it would be rather expensive to put one on every piece I've got.

I got into a really nice TEFC 10hp 3 phase motor. I'm thinking of turning it into a converter, so I could run my surface grinder and hydraulics, and still have power to run my mill or drill presses at the same time to multi-task.

I pass up a lot of screaming deals on 3 phase welders too, which I could likely run just fine with a rotary.

I understand the general principle but get lost in the smaller details like what kind/size of capacitors, switches, how to rig a pony motor, etc.
 
I bought this on a whim at an auction thinking if it was the right size (there were no details in the auction) I'd use it to power a hammer down the road, but it's just way too damn big for that. For $30 it was worth a try. Kind of a shame to split the motor to build an RPC but the limited application for these things makes selling it for enough to buy a phase converter unlikely.
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google Phase-craft and go to their store. they offer a 10Hp rotary phase converter control unit for about $200, there are others around also for same price. all you need to do is attach the wires. just a thought
 
We used to use a roto-phase. Last year we purchased a Phase Perfect which is a digital phase converter. It was much more expensive than the roto-phase, but it has almost paid for itself in energy savings.

Chuck
 
Alpha Knife Supply said:
We used to use a roto-phase. Last year we purchased a Phase Perfect which is a digital phase converter. It was much more expensive than the roto-phase, but it has almost paid for itself in energy savings.

Chuck
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Chuck were you running the RPC all the time? I know the digitals are more efficient and would eventually pay for itself, but even if it's 1500 watts to idle it would take me a long time to pay for a $3,000+ digital.
 
scott.livesey said:
google Phase-craft and go to their store. they offer a 10Hp rotary phase converter control unit for about $200, there are others around also for same price. all you need to do is attach the wires. just a thought
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Oh god thank you. That's definitely worth $200 to me. The minutia of wiring and sourcing components for stuff like this makes me want to put my head in the forge.
 
We only used the roto-phase while running 3 phase tools. Now we run the Phase Perfect 24-7. The savings on our power bill is $200-$250 per month.

There are other benefits to the Phase Perfect. The voltage is digitally balanced to +- 1%. The tools run much smoother. If you decide to get a CNC mill, you will be ready with clean balanced power.

Chuck
 
I have a Phase Perfect too. It's great. Rotary converters will sometimes do a poor job of powering a 3 phase welder, Phase Perfect is about the best conversion method I'm aware of for that. I'll be running my big hammer off the PP too, as my VFD only goes up to 3 hp. just thought i'd add that about welders, might want to do some reading around the net concerning that.
 
I didn't realize how much power an idling RPC uses. I put an amp meter on one here and it was drawing almost 40 amps idling. We run two of those. :eek:


...might be time to bite the bullet on a Phase Perfect, though the big ones are a little spendy...
 
480 or 240 doesn't matter, you pay for watts used. 1 kilowatt is the same whether 120 or 240 or 480. 480 just lets you use half the current than 240, but you have to have cable rated for 600v instead of 300V. 10hp would need 8awg cable for 240 but only 12 awg for 460. at home not much difference. on a aircraft carrier with literally miles of copper wire, having 1320 volt mains saved tons of weight.
 
kuraki said:
So, how many watts was Nathan using?
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40 amps at 240 volts is 9600 watts (there is actually a little more to it than that, but this is simple and probably pretty close), which costs about $1 per hour, which jives with my power bill.

ETA: That's a lot of power. My electric water heater is only about 5,000 watts. The fact it isn't generating a huge amount of heat tells me there is some power factor compensation magic I'm not considering. This has to do with different kinds of loads and amp draw across the sine wave that I don't really know much about, I'm not an electrical engineer and there are RMS type meters that could probably make a better measurement. Like most things, I think it's actually a little more complicated than we were taught in HS physics...
 
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Nathan the Machinist said:
I didn't realize how much power an idling RPC uses. I put an amp meter on one here and it was drawing almost 40 amps idling. We run two of those. :eek: ...might be time to bite the bullet on a Phase Perfect, though the big ones are a little spendy...
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by idle, you mean there was no load on the 3 phase produced but that the motor being driven by 240 single phase was turning? was the 40 amps read on the single phase line(don't know how big the setup is?)
 
Consider American Rotary also. I've been running one for years, and very happy with it after I blew up my home built one.


Go ahead and spend a few bucks for something CNC ready and digitally controlled.

They have a chart listing the idle power consumption based on a certain watt hour rate. Wanna say my 10hp model was listed at like 6 or 12c an hour idle. I leave it running for days often, and don't notice the difference in power. In fact, there's more month to month rate variation just from the power co's ever changing peak rate season bs.

FYI they also have an ebay store where their prices are often a fair bit better than catalog prices.

Only problem I have is that I didn't buy a bigger one, wish I had gone with a 20hp at least. New shop is getting 400 amp service from power co, but no 3 phase, at that point I'll be buying a 30 or 40hp model probably and hard wiring everything.


I've got a few friends that I've suggested get them that have bigger ones from the same company and have been very happy with them. The variety that use an idler motor have specially made baldor motors without ever having a shaft protruding for example, but I think they've also got all digital models also, obviously, they're more expensive.
 
" ... My electric water heater is only about 5,000 watts. The fact it isn't generating a huge amount of heat tells me there is some power factor compensation magic I'm not considering...."

Nathan, what is missing in the equation is that the rotary converter runs full time. The water heater only uses electricity when it needs to heat the water up a few degrees. The draw is 5000W, but the duty time may be only 5-10 minutes per hour, unless you are taking a shower. Power is paid for in kilowatt hours, so 5000 watts drawn for only 10 minutes in an hour is .5KWH. The phase converter drawing 9600watts is using 9.6 KWH.
 
another option would be to find a Government Liquidation sale of a diesel generator. there are a couple of 60kw (440 3 phase 105 amps) just down the road from Stacy that will sell for $1000 or so. there are a bunch in Ohio, same size, that are made by John Deere. there are several small sawmills nearby that use big diesel generators to power their big saws and conveyors.
 
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