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single phase vs 3 phase compressor (already have phase converter)

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River Runner

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Good day,

I will need a bigger compressor for my operation, 30 cfm minimum. I will already have a Phase Perfect converter to run my 3ph 480 volt CNC. My question is does it make more sense to get a 3phase unit and run in off the converter vs a large single phase compressor? The CNC and the compressor would not be needed at the same time as the compressor will be used for polishing the cut pieces. The CNC does require a small volume of air to operate but that could be supplied with my current 10cfm 240v compressor.

For simplicity sakes I would think just one big single phase would be easiest but I'm trying to think ahead in the event that someday I am able to get into a bigger facility with 3 phase power should business increase.
 
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Chuckster in NJ

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You can get a single phase for now and when you move it will be easier to sell or you can "invest in the future" and buy a 3 phase.…….. "IF" you are definitely/positively moving within the next few years I would go with a 3 phase.
 
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theoldwizard1

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You are losing energy converting from single phase to three phase (Second Law of Thermodynamics).

Having said that, I don't know if you can find a single phase compressor capable of 30 CFM ! What are you running ?

I used to work in a large garage. Over 20 stalls. The air storage tank was probably over 250 gallons. 2 pumps, 2 motors. To get that volume of air to where you need it, you will likely need 1" pipe and 1" hoses.
 
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cannuck

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You actually CAN get a 30 SCFM compressor that runs on 250VAC (7.5 HP). You just need to see that it is rated for 100% duty cycle (if your application actually USES 30 SCFM). If you are going to buy used, the hot tip is that 3 phase stuff sells for far less than single phase. The downside is that the lower end of the power range is not nearly as common (at least around here) in 3 phase as bigger power. I find that you can get some genuine bargains in 10HP and over range (I bought a very low hour 30HP screw last year for 3HP recip prices) that makes the option of a screw with a dryer possible (WAY quieter and long lasting than a recip, but my 3HP recip is well over 60 years old and still going strong so not so sure that part is applicable).
 
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marinusdees

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River Runner said:
Good day,

I will need a bigger compressor for my operation, 30 cfm minimum. I will already have a Phase Perfect converter to run my 3ph 480 volt CNC. My question is does it make more sense to get a 3phase unit and run in off the converter vs a large single phase compressor? The CNC and the compressor would not be needed at the same time as the compressor will be used for polishing the cut pieces. The CNC does require a small volume of air to operate but that could be supplied with my current 10cfm 240v compressor.

For simplicity sakes I would think just one big single phase would be easiest but I'm trying to think ahead in the event that someday I am able to get into a bigger facility with 3 phase power should business increase.
Click to expand...
In general, air compressors don't do well on phase convertors. Starting (inrush) current, not running current, is a problem.
 
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sparky 1971

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theoldwizard1

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sparky 1971 said:
Here you go. 38 CFM at 100psi. I have a customer with the same thing, but a 120 gallon tank along with another 120 gallon storage tank. For a hobby garage.

eatoncompressor.com

10 HP Quiet Air Compressor, Single Phase, 80 Gallon Tank, Vertical

Eaton Compressor carries an impressive line of quiet air compressors, including this single phase 10 HP Quiet Air Compressor with 80 Gallon Tank.
eatoncompressor.com eatoncompressor.com
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Big tanks are great ! Just make sure the plumbing can deliver the volume.

I would also check out TWO non-commercial 5 HP units feed another tank. When you don't need the big volume, you on!y have to run one.
 
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u3b3rg33k

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my 10HP Eaton VFD compressor at work comes with an oversized VFD, specifically so it can be either 1ø or 3ø 240V.
 
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alfredeneuman

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kaffine said:
He didn't say he has 480V single phase. Just that he has a phase converter to run his 480V 3 phase CNC. Could be using step up transformers to power the CNC.
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What way do you interpret this ?
River Runner said:
My question is does it make more sense to get a 3phase unit and run in off the converter vs a large single phase compressor?
Click to expand...
The OP asked this question and hasn't come back since. Only he knows for certain.
 
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kaffine

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alfredeneuman said:
What way do you interpret this ?

The OP asked this question and hasn't come back since. Only he knows for certain.
Click to expand...

With a little common sense. I know 480V is not a common single phase voltage therefore a step up transformer is more likely than him having a non standard single phase supply. You are right that only the OP knows for certain, I am making an assumption.
 
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alfredeneuman

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kaffine said:
I know 480V is not a common single phase voltage therefore a step up transformer is more likely than him having a non standard single phase supply.
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I am in full agreement with that. (The OP shouldn't have left 10 minutes after he posed the question.)
EDIT: Where I live Southern Cal Edison offers 240/480 single phase services, but I think it's for billboard and signage use.
 
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jar944

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u3b3rg33k

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$3k extra spent to run a single appliance, why not just get the fancier appliance with the integrated VFD?
 
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jar944

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u3b3rg33k said:
$3k extra spent to run a single appliance, why not just get the fancier appliance with the integrated VFD?
Click to expand...

What is 3k extra? He already has 480v 3ph from the PP. The question is single phase or 3p motor on the new compressor.

I'd go 3 phase every time.
 
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u3b3rg33k

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jar944 said:
What is 3k extra? He already has 480v 3ph from the PP. The question is single phase or 3p motor on the new compressor.

I'd go 3 phase every time.
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another phase perfect rated for 10HP. unless his current one has the spare surge ampacity to start a 30CFM compressor (10hp, IIRC) DOL, which seems unlikely. without info on his existing converter, I erred on the side of "what u got ain't big enough".
 
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u3b3rg33k

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jar944 said:
Its a PP not a vfd, they have the option to output at double the voltage of the input, depending on model without adding a additional transformer.

Phase Perfect Enterprise | Single to Three Phase Power Converter | Variable Frequency Drives and Digital Phase Converters | Phase Technologies

www.phasetechnologies.com www.phasetechnologies.com
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VFDs can have that feature, too. I have a handful of 120V 1ø in, 240v 3ø out, VFDs. I was more surprised by this:
The Phase Perfect® will also return power to your single-phase source when any three-phase load is in generating mode. Returning this power and making your utility meter run backwards is a much more efficient solution than wasting any excess power by heating a resistor.
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but from the look of the pictures, they pass L1, L2 through and generate L3. my guess is only two legs pass power back through. probably works just fine.

or a phase converter to generate three-phase power, the two incoming power lines are directly passed through to the output and the phase converter generates the third leg in a configuration known as “high-leg delta.” This will power most three-phase machines. Some machines however require wye-configured power, which includes a neutral. If your machine requires wye-configured power, you will need to send the output of the phase converter through a delta-to-wye transformer before the load. In the graphic below, T3 is the generated leg.
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seems like that's what they do
 
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