Energy use of Phase Perfect versus Rotary Phase Converter

I know this has probably been discussed to death, resurrected, then discussed back to death, but for the life of me, I can't find it.

I'm moving some equipment into my garage at home, which currently has a fairly undersized electrical service. I plan on upgrading the house to 200 amps, and will be putting in a separate subpanel of a yet to be determined size (for a combined electric service probably in the 400 amp range.)

Going into the garage is:

1. 7.5 HaasPower CNC, three phase
2. 3/4 hp Saw, three phase
3. 1 hp Surface Grinder, three phase
4. 1 hp Compressor, single phase
5. 1 hp Belt Sander, three phase
6. 1/2 hp Pedestal Grinder, single phase

At most, I'd be running one of piece of equipment while the CNC runs.

I don't have, and cannot get, three phase power at the house, so I'm going to need a phase converter of some variety...right? Looks like I'll need an RPC rated for at least 15hp, correct? I don't know how the phase perfect units are sized, but I'll guess I would need at least 15hp there as well.

I have a basic understanding of how these types of things work (magical pixies make spindles move) but I was curious about power consumption. A rotary phase converter will have a decent sized motor running all the time, correct? I see that they list the 'cost to run per hour' on some of the models I'm looking at - does 23 cents an hour sound realistic? Is it crazy to think just the electrical cost of running the equipment will be a couple of bucks an hour?

I see American Rotary is selling 15hp units on FleaBay for $1049, and I can find a Phase Perfect PT-330 online for $3390. Am I missing something in how I might make up the $2341 difference? Power savings? Hassle?

Is there a better option than American Rotary for an RPC, or Phase Perfect?

Johnny SolidWorks said:

I know this has probably been discussed to death, resurrected, then discussed back to death, but for the life of me, I can't find it.

I'm moving some equipment into my garage at home, which currently has a fairly undersized electrical service. I plan on upgrading the house to 200 amps, and will be putting in a separate subpanel of a yet to be determined size (for a combined electric service probably in the 400 amp range.)

Going into the garage is:

1. 7.5 HaasPower CNC, three phase
2. 3/4 hp Saw, three phase
3. 1 hp Surface Grinder, three phase
4. 1 hp Compressor, single phase
5. 1 hp Belt Sander, three phase
6. 1/2 hp Pedestal Grinder, single phase

At most, I'd be running one of piece of equipment while the CNC runs.

I don't have, and cannot get, three phase power at the house, so I'm going to need a phase converter of some variety...right? Looks like I'll need an RPC rated for at least 15hp, correct? I don't know how the phase perfect units are sized, but I'll guess I would need at least 15hp there as well.

I have a basic understanding of how these types of things work (magical pixies make spindles move) but I was curious about power consumption. A rotary phase converter will have a decent sized motor running all the time, correct? I see that they list the 'cost to run per hour' on some of the models I'm looking at - does 23 cents an hour sound realistic? Is it crazy to think just the electrical cost of running the equipment will be a couple of bucks an hour?

I see American Rotary is selling 15hp units on FleaBay for $1049, and I can find a Phase Perfect PT-330 online for $3390. Am I missing something in how I might make up the $2341 difference? Power savings? Hassle?

Is there a better option than American Rotary for an RPC, or Phase Perfect?

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Download the manuals and brochures of their makers, please. Efficiency is stated.

It is actually difficult to build a BAD RPC, but some are better than others. Mine is a Phase-Craft, Brazilian-made 10 HP Weg motor as idler, both bought new, on-site assembly and wiring per Jim's instructions. Dirt-simple.

If Phase-Perfect even has ANY effective competition it is a well-kept secret. Mine was bought used, older 'blue paint' model.

Except for CNC-class loads, I essentially have 'all of the above', as-in 'native' 3-Phase 12 kW capable Diesel gen set, 10 HP Phase-Perfect, 10 HP RPC, 200 A service entrance, max 7.5 HP 3-Phase motor load.

A good, well-sized, well-balanced RPC generally drives a load-motor to around 90% of its nameplate, may need switchable balancing caps for different loads even to do that, and may fall a tad off-perch if its load is highly variable as to power needed. OTOH, an RPC is exceptionally rugged - bordering on 'bulletproof' - if unforeseen things happen, and on either side of it. "Good enough" for tens of thousands of folks if not millions.

A Phase-Perfect IS 'perfect enough' to drive its loads to 100% of nameplate, and handle varying load better. It is not quite as rugged as an RPC, but is 'rugged enough' that failure is very, very, uncommon. Rare for anyone who has one to want to give it up unless trading-up to a larger size or shutting down the biz.

The gen set is no different in quality from utility-mains 3-Phase, save that its frequency is not precisely locked to a global 'clock'. OTOH, it is smelly, and fuel and the maintenance of stored fuel are a costly nuisance. Given that it is ALSO my emergency power source for the entire residence, I can live with that.

If I had CNC? I'd start with the Phase-Perfect. The Haas will appreciate it. A Surface grinder would be another candidate. Compressors are annoying bed-partners on a shared power source. I'd want that on an RPC, minimum double the compressor load rating, four or more times better-yet, just so starting is not an issue.

So.. if more money was there, the compressor and all other more forgiving tools would go separately onto an RPC as it could now be a smaller one. 7.5 HP or even 5 HP should do, DIY or 'kit build' with your own motor, such as Phase-Craft does is cheap and easy, and the harmonic distortion a smaller RPC pumps BACK up the line less of a bother to the Powerco, your neighbours, and your own residence.

Take your pick. More than one is allowed. Used-but-good works. You are allowed to change your mind later, and more than once.

I'm not sure you can live long enough to recoup the energy savings but after years of a Kay RPC, I'm a diehard PP fan. Quiet and balanced from high to low amperage. I'm not sure a RPC balanced enough for your 7.5 hp CNC and balanced for your small motors can be had for $1000 so the differential might be less. My 10 hp PP started a ten hp motor easier than my 10 hp Kay which is rated similar to a 15-20 hp AR. Dave

beckerkumm said:

I'm not sure you can live long enough to recoup the energy savings but after years of a Kay RPC, I'm a diehard PP fan. Quiet and balanced from high to low amperage. I'm not sure a RPC balanced enough for your 7.5 hp CNC and balanced for your small motors can be had for $1000 so the differential might be less. My 10 hp PP started a ten hp motor easier than my 10 hp Kay which is rated similar to a 15-20 hp AR. Dave

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If I had no P-P, I'd have to add a 5 HP or 10 HP 'supplementary' idler to the RPC to assure good starting, even of the 7.5 HP Alzmetall DP, and may do just that, as I don't want the unpredictable load bugger on the P-P.

That second idler could be shed if a load machine were to be left running, but still... the P-P was quite affordable, used, even with palletizing, long-distance shipping, and lift-gate residential delivery.

Just not easy to find, used. Those who have 'em tend to keep 'em.

Monarchist said:

It is actually difficult to build a BAD RPC, but some are better than others. Mine is a Phase-Craft, Brazilian-made 10 HP Weg motor as idler, both bought new, on-site assembly and wiring per Jim's instructions. Dirt-simple.

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I got a Weg motor as a replacement in a warranty type situation. Solid and heavy. Good motor.

Johnny SolidWorks said:

I'm moving some equipment into my garage at home, which currently has a fairly undersized electrical service. I plan on upgrading the house to 200 amps, and will be putting in a separate subpanel of a yet to be determined size (for a combined electric service probably in the 400 amp range.)

Is there a better option than American Rotary for an RPC, or Phase Perfect?

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My only suggestion is to trade up and buy the bigger PT-380 (30hp) model so you will not outgrow it in the future. I have seen several PPs for sale here only because the owner either installed 3 phase or needed a bigger model. Never have I seen a PP being sold because it was too big.

My PT-380 uses about 400 watts of power idling per their literature. I use my PP to power everything in my shop from a 1/2hp drill press to my 30hp CNC lathe. Been in use for 5 years. Best thing I ever bought for the shop after the ductless A/C system.

Johnny SolidWorks said:

Going into the garage is:

1. 7.5 HaasPower CNC, three phase
2. 3/4 hp Saw, three phase
3. 1 hp Surface Grinder, three phase
4. 1 hp Compressor, single phase
5. 1 hp Belt Sander, three phase
6. 1/2 hp Pedestal Grinder, single phase

I see American Rotary is selling 15hp units on FleaBay for $1049, and I can find a Phase Perfect PT-330 online for $3390. Am I missing something in how I might make up the $2341 difference? Power savings? Hassle?

Is there a better option than American Rotary for an RPC, or Phase Perfect?

Click to expand...

Phase Perfect generates the third phase by digital modulation. I have reviewed their literature and give thumbs up.

Another option is to have a 10Hp and a 5Hp RPC. Run both when Hassiing away, otherwise just run the little 5Hp with the other tools. Both can be built by you with a price way less than $3390.

rons said:

I got a Weg motor as a replacement in a warranty type situation. Solid and heavy. Good motor.

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LOL! Well I'm a Reliance guy, so I regard mine with a bit lesser regard. But 'brand new' and 'not Chinese' were plusses. Beside, the founders of Brazil's Weg were expat Germans, so.."fit for its purpose" well-enough I'd buy another.

RPC are rated at the biggest motor they well start ,,, not the full HP they can run at one time ,,, I ran two fadals off one 20 HP RPC for years and it worked great,,, both machines were ran off a single 60 amp input. if your talking 7 1/2 Haas power your only looking at a 4 or 5 hp motor tops ,,, even my new VF4SS that haas calls 30 HP only has a small 7.5 HP motor in it ... so yes a 15 or 20 HP RPC would work out fine for you ,,, as for them using power to make power yes but the "ONLY" loss is in heat and its not a lot ,,,
In NY you would use the heat for your shop 6 or 8 months out of the year anyways ... one HUGE upside to using a RPC is you can fix them cheap and there simple ,,,

Sizing is different with each company. Some size by the largest hard start motor, but most size by largest easy start which works out to 1.5-2x difference.

If looking at used for PP, the 20 hp unit seems to be priced better than the 10 hp as I suspect the 10 is most popular among the hobby guys. I picked up a 20 hp just for a back up and plug it into a 50 amp welding recepticle. Works just fine but doesn't have full capacity. Dave

My opinion is that PP is an absolute beautiful converter. I've worked with them, around them, Been shops that use them.

To compare apples to apples, a PP will do 90% of what it is designed for. A RPC Will do about 50 to 60% of idler size. But if you're OK with electrical work and salvage, you can build an 20-30hp for under $200-500. I built my portable RPC that has 20 hp Idler, a 600 V transformer, it'll run off 40-100A Single phase . It ran me about $700 Canadian which is like $400 US. When I say portable, it's on wheels. The whole unit weighs about 450 pounds. At 12 hp load it starts to see some voltage lag. At idle, I'm wasting 5 A at 240 V (single phase) with three-phase transformer energized. My idoler consumption is reduced by about 30% when I have a load. Most of my numbers are calculated. My Hydro bill went down recently from $300 a month to $200 a month. But I installed natural gas heating instead of electrical heating. I usually take two months off during the summer and a month during the mid winter and I am (mostly)a one-man shop. My shop electrical bill is about $80-$100 per month more (can) when I am working. I couldn't justify a PP as it stands right now. I used to have 2 x 5 hp's RPCs, now I have one 5 hp RPC and I use the 20 hp portable unit when the need arises. Based on my needs, I might be selling the 5 hp RPC and 6 kva transformer this summer and just running everything off the 20 hp and 15 kVA transformer portable unit. Sorry if I've rambled on.

Based on my calculations and how I run my RPC, a PP would not pay off in the next 20 years.

my air compressor, tablesaw, lathe, drill press, small press, large press, and one bandsaw all run on sp=>3p VFD's.

PP vs RPC in 10 years, my bet for longevity is RPC.

Matt Matt said:

At 12 hp load it starts to see some voltage lag.

Based on my calculations and how I run my RPC, a PP would not pay off in the next 20 years.

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I bought my PP based off the fact it maintains a constant voltage over any load. My 30 year old CNCs do NOT tolerate voltage imbalance well at all. Fed proper power, they are proven to last a long time. Been proving that at work for the last 20 years.

I figured out the difference between a RPC and a PP for me was less than the cost of one spindle drive repair. I bought the PP literally as an insurance policy against electrical failures in my CNCs. Been working great the last 5 years with the stable voltage diet.

Second reason I bought the PP was to squeak the most out of my 200 amp garage service. I can run my two CNCs with no problem and run the 15 hp turret lathe and the 7.5hp air compressor all at the same time.

If I had no CNCs to worry about, then I would still be using an RPC.

Bet your PP is blue if it has been around a long time. Word has it they can no longer fix those, so you may be investing again if it has a problem. But they arepretty trouble free, as I am told (and would expect).

JST said:

Bet your PP is blue if it has been around a long time. Word has it they can no longer fix those, so you may be investing again if it has a problem. But they arepretty trouble free, as I am told (and would expect).

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Not sure who this comment was directed at but I bought my white PT-380 brand new in July 2012.

Philabuster said:

I bought my PP based off the fact it maintains a constant voltage over any load. My 30 year old CNCs do NOT tolerate voltage imbalance well at all. Fed proper power, they are proven to last a long time. Been proving that at work for the last 20 years.

I figured out the difference between a RPC and a PP for me was less than the cost of one spindle drive repair. I bought the PP literally as an insurance policy against electrical failures in my CNCs. Been working great the last 5 years with the stable voltage diet.

Second reason I bought the PP was to squeak the most out of my 200 amp garage service. I can run my two CNCs with no problem and run the 15 hp turret lathe and the 7.5hp air compressor all at the same time.

If I had no CNCs to worry about, then I would still be using an RPC.

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Not to be "that guy" but there has to be some variation in supply to the CNC out of the Phase Perfect - it's just a matter of how much, right?

.05%? .5%? 5%? I'd guess less than 1% or better for the phase perfect, but on the phase craft that are stated to be for CNCs, they're claiming less than 2% variation. Is that realistic? I have no clue, but if I had to take a guess, in my area, I'd think 3 phase power directly from the power company would vary that much.

But I'm no expert on any of this stuff, and your concern about blowing a drive trying to save a couple of bucks on the converter is very valid, and one I hadn't thought of.

How many members are running 15 year old CNCs on RPCs? Anybody ever fried a servo drive due to power variations?

The PP has ALL SORTS OF VARIATION IN OUTPUT it is not at all constant.

The PP does not supply all 3 wires, so all it does is keep the BALANCE correct. The actual voltage variations go right through, the PP keeps the 3rd wire in sync with the line voltage changes.

Philabuster said:

Not sure who this comment was directed at but I bought my white PT-380 brand new in July 2012.

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Was you, since you talked about having the CNC for 20 years or so.... If you have a new one, you are good for the present.

JST said:

Was you, since you talked about having the CNC for 20 years or so.... If you have a new one, you are good for the present.

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To clarify, I bought the same 1986 vintage Mazaks for my home hobby shop that I am still running at my real job 20+ years later.

One thing I just recently read from a .pdf on the PP website was the line filter capacitors need to be tested or swapped out every 3 years. Looks like I am overdue.

http://www.phasetechnologies.com/downloads/products/phase-perfect/Op & Install Phase Perfect.pdf

Using a multi-meter set to measure capacitance, check the capacitance of each capacitor by measuring between the two terminals on the capacitor.
Remove the wire from at least one terminal of the capacitor in order to obtain an accurate measurement.

Compare to the capacitor value in Table 7. If any capacitor value is less than specified by more than 25% contact Phase Technologies customer support at 605-343-7934 to order replacement capacitors.

If you do not have a meter or other means to test the capacitors it is recommended to
replace the capacitors every three years as a preventive measure. Do not operate the converter with degraded capacitors!

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Zowie......

They must work the crap out of them, or they know something "interesting" about the deign. If the caps have voltage on them regularly, they should last more than 3 years. MIL would want longer than that, and might use the same parts in a "COTS" design.

JST said:

Bet your PP is blue if it has been around a long time. Word has it they can no longer fix those, so you may be investing again if it has a problem. But they arepretty trouble free, as I am told (and would expect).

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Phhtt. They may have CHOSEN to no longer support those. Cost-benefit exercise.

Mine is a blue one. If it needs fixed, it will get fixed. They are patented, not encrypted.

Monarchist said:

Phhtt. They may have CHOSEN to no longer support those. Cost-benefit exercise.

Mine is a blue one. If it needs fixed, it will get fixed. They are patented, not encrypted.

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Mmmmmmmmmmmm.................

Problem may be something actually unobtainable, or something they do not want to fiddle with. I was actually told that a specific PC assembly is the issue, exact reason not known, but guessable.

For example.... Many VFDs use a power module (IGBT/Rectifier/Brake) that is no longer available, because those things change every few years. There WILL be one in a new package to do the same job, of that you can be pretty sure. But if it does not fit in the old PWB, it is not usable, and it is pretty certain not to fit..

Same with other parts, they go obsolete, and are available only from the vendors who buy up obsoleted and surplus parts specifically so that they can later charge "we know you REALLY NEED this part" rates. Sole source vendors in many cases. Parts that were 25 cents now cost $10. Each.

PT is not likely to design a new version just to maintain old units, so for most folks it means no parts. To "repair" it means a "design project", which some folks are qualified to do, and others are not. Rapidly becomes an uneconomical use of time of you are normally billing out at engineering rates.

Frankly, they might actually find it worthwhile to have a replacement part, for the "we can repair any machine we ever made" points. Nobody says they have to give away the parts..... just make it low enough to convince most to not scrap the old one. Plenty of folks have not bought a PP yet, and dollars don't care where they come from.