Who has an air compressor with a phase converter.

[Tractor Seabee]

There is a lot of info on motor starting methods such as this one:



Ron

 

[ultrarunner]

You could try to reduce the inrush current. Most compressors have an unloader. The problem is that the pipe between the compressor and check value is short and the compressor quickly gets loaded while it's still ramping back up to speed. You could take it a step further by having the compressor just vent to atmosphere for a few extra seconds with an electric valve before closing so the motor starting up and the load of compressing air are separated.

I have a very old Devilbiss Commercial Compressor that has a built in unloader... the motor never starts under load and this 1950's compressor is remarkably quiet.

 

[claya]

What have you done to resolve getting power to this compressor? 3Phase, or switch over the motor to single phase?

I have a 40Hp RPC, running a Machining center, and am looking at this exact same compressor. Would also like to cycle the converter ONLY when the compressor needs air.

clay

As the title says, would here is running a 3 phase air compressor with a phase converter.

I acquired a joy twistair ta010. Not sure the cfm but it's pretty good. It will charge it's 80 gallon horizontal tank from 0 paid to 120 paid in about one minute flat.

But ran low on oil and locked up. So I am gonna look into a rebuild as it is a nice compressor.

It has a 10 hp motor.

I am no stranger to phase converters and vfd's.

I have a 10hp rotary that is running a mill and lathe currently. And another 15 hp rotary not used now. And a 5 hp vfd I use for the log splitter.

If I need to use the mill or lathe, it's no problem to just push the button and start the rotary.

However....the compressor I just want to be like my current one. Plugged in ready to do it's own thing whenever it needs to charge. Don't want to have to worry about starting a phase converter Everytime I want a little air, or Everytime it needs to kick on. But also don't want to leave the rotary running 24/7 either.

So those that are running a 3phase compressor off a converter.....what setup are you using?

 

[LD1]

I went with a single phase 10hp / 240v motor.

Sorry i never updated thread

 

[Industrial Toys]

Best thing! I bought a BIG Lincoln Welder at an Auction by accident that was only three phase. I built a nice 10HP 600 Volt phase converter. Then got a drill/milling machine. What a pain to stop and start a phase converter. I sold everything 600 volt and bought a Lincoln 220 volt MIG. I don't even know how you would stop and start a rotocon for a compressor.

 

[LD1]

Starting and stopping the phase converter is no big deal for things like the mill and lathe. Just two buttons to push to start the lathe I stead of one.

But the air compressor was a different animal. It starts and stops on its own whenever it needs to. Sure, one can wire up the phase converter to the pressure on off switches....and a start up timer to give the converter a few seconds to get up to speed before starting the compressor.

But at the end of the day, it was just easier to get a single phase motor. And if I happened to be turning something heavy on the lathe.....and the 10hp compressor decided to kick on....that probably wouldn't be good unless I went even bigger on my phase converter

 

[claya]

What motor and pulley setup did you go with? And can you measure cfm? I need a bare MINIMUM of 28cfm, and probably 40cfm is better in my situation. But, Pretty sure running my 20hp spindle on the MILL (VMC) when the compressor kicks on will be bad, if I keep the compressor 3ph, as suggested. Sent a couple PM's. Did you get them?

 

[Industrial Toys]

My 10 HP Rotocon draws insane amounts of power on startup. Not something you want to be starting and stopping every time you want to drill a hole. It's possibly not even allowed by the utility to suck such inrush currents!

 

[LD1]

What motor and pulley setup did you go with? And can you measure cfm? I need a bare MINIMUM of 28cfm, and probably 40cfm is better in my situation. But, Pretty sure running my 20hp spindle on the MILL (VMC) when the compressor kicks on will be bad, if I keep the compressor 3ph, as suggested. Sent a couple PM's. Did you get them?

10hp single phase motor. Pulleys are the ones that came with it. Not sure exactly what you are asking for.

No way to measure actual cfm.....other than it charges the 80 gallon tank to 110psi in 3m25s.

Doubt that I am actually getting 40 cfm.

The head was locked up when I got it. So lots of trash went through the rotors. But with these types of compressors they will still make air, just less of it.

My old 9cfm piston type takes 4 minutes to get a 30 gallon tank to 110psi. So I am definitely getting alot more air.

I haven't changed the separator filter yet either, so I'd probably gain a little there too

 

[claya]

You had mentioned changing the pulley ratio to maintain the cfm/pump rpm etc.. From what psi to 110? Will help some in estimating the cfm. Or is the tank empty to 110psi in 3min25s?

I need at LEAST 30cfm, bare minimum. Have not bought the Twistair, yet. Just following your lead, and doing the maths. I expect to need to rebuild the pump bits on the one I am looking at. Expect it has LOTS of hours on it. I have the chance to buy a much newer, yet more expensive to run/maintain 15hp Ingersol.

Which motor #? You listed several choices. I need to consider the $$$ and amp load of running yet another 7.5-10hp on my 200A panel. Plus, I only have 25kva on the pole feeding two houses, and 3 shops. So expect to get some heartburn from the utility company, once I start pulling some serious amps.

 

[LD1]

I dont remember the motor I used. I think it was a marathon. But that dont really matter.

It was a 10HP 3450rpm motor. Same as the 3-phase that came off but just 240v single phase.

Forget all the talk of changing pulleys. I only was contemplating that because the airend (compressor head) is the SAME joy used on 3 different models. Ranging from 29 cfm when paired with 7.5hp, 40cfm when paired with 10hp and 60cfm when paired with 15HP. The ONLY difference in the three compressors other than more HP was changing pulleys to make the pump spin faster.

I was gonna drop to 7.5hp and change pulleys to basically have a TA007 compressor @ 29cfm. Because 7.5HP motors were cheaper.

You could go the other route and get a 15HP motor and spin the pump up to get 60cfm. Thats all the MFG did for their TA015 model.

And my 3m25s was from 0psi to 110

 

[claya]

3m25s is ~23cfm. What kind of inrush amps are you measuring? What size breaker are you running it off of?

I dont remember the motor I used. I think it was a marathon. But that dont really matter.

It was a 10HP 3450rpm motor. Same as the 3-phase that came off but just 240v single phase.

Forget all the talk of changing pulleys. I only was contemplating that because the airend (compressor head) is the SAME joy used on 3 different models. Ranging from 29 cfm when paired with 7.5hp, 40cfm when paired with 10hp and 60cfm when paired with 15HP. The ONLY difference in the three compressors other than more HP was changing pulleys to make the pump spin faster.

I was gonna drop to 7.5hp and change pulleys to basically have a TA007 compressor @ 29cfm. Because 7.5HP motors were cheaper.

You could go the other route and get a 15HP motor and spin the pump up to get 60cfm. Thats all the MFG did for their TA015 model.

And my 3m25s was from 0psi to 110

 

[LD1]

3m25s is ~23cfm. What kind of inrush amps are you measuring? What size breaker are you running it off of?

Not sure what inrush is.

once running....at little to no pressure....it pulls ~20a. Then creeps up just a tad above the motors FLA rating (which is 38 or something)....and when the compressor kicks off at ~110-115psi it is 40a. But it is only above the FLA rating for maybe 15 seconds. (as pressure increases it requires more power). 1.15SF motor this shouldnt be an issue.

Startup isnt alot either though. The compressor starts "unloaded".....then it gradually loads to start making air.

I dont know the proper way to calculate. But if you convert PSI to ATM's....figure cubic feet of air....and divide by time......it just doesnt seem to work on any compressor I have calculated it with. And when I was talking to some compressor engineers, they were explaining that it wasnt just a simple equation like that, but dont really remember why. But they also pointed out that compressors have a HIGHER rating at 40psi than they do at 90psi. And the simplistic equation doesnt account for that, so there is more too it.

I dont doubt that I am running LESS than the MFG claimed 40cfm. Again, intake and separator filter are in need of replacing. But there is also a good delay at startup while things are running but the compressor isnt "loaded".

I know I am not being much help. But if you NEED a minimum of 30cfm.....what PSI is that at. I wouldnt be confident that even a NEW 40cfm screw compressor would be what you want. Dont want to have issues everytime a filter is a month old, or as things start to wear

 

[claya]

Actually this helps quite a bit. Inrush is basically startup current. But on a compressor it is the end of the cycle. So you have answered that.
I used a simple online compressor CFM calculator, so the 23Cfm is likely on the low side. I expect the formula is complex. I need 30cfm @ ~100psi average.

Borrowing a big piston compressor this week to find out what we really need. It sounds like 10HP is probably the bare minimum. So we may need to consider a 15HP motor. 40A, I think we can handle, but is nothing to sneeze at either. Of course 15hp is a lot more current, and I have not yet seen a 15HP single phase motor. A buddy is upgrading from a 15HP variable speed, so we might buy that. Your experience and answers have been very helpful. Thank you.

If you hook up the compressor to to an RPC for automatic start, like to hear your results on that. We have a separate RPC we may run a 3Ph compressor on instead of converting one to 1Ph. But it will need to be auto start. I don't want to leave the RPC running all the time just to cycle the compressor.

 

[Industrial Toys]

I don't know if it has been mentioned. Why not go with a freq drive? It's a much better although more fragile way of making 3 phase with single phase and you don't have the crazy high inrush currents as with a simple RPC. But, you need to DERATE the freq drive when using single phase AND make sure you get one that will even do that. Some will not work with single phase. I converted a friends lathe and mill over to freq drives and he just loves the speed and direction contol.

 

[claya]

This is a VMC, with a 20HP spindle and a zillion other motors. RPC is the only option or pay $$$$$ to have the local utility bring 3ph down our driveway. 10 yrs ago that was ballpark quoted @ $10K. Expect it is at least double that now. We have some pretty serious energy issues here in Cali. Both Nuclear plants have been shut down permanently by fools who seem to be happy to pay one of the the highest energy rates in the country. And we now have a time-of-day Rate structure.

 

[Industrial Toys]

Apparently, here, you can't afford three phase service unless you are a big user. The delivery charges are very high.

 

[ultrarunner]

Several of my friends have removed it from their warehouses... they were not using it and the standby charge even 20 years ago was $75 a month...

My Rotary Phase Convertor has a pony motor to start... the small motor spins up the convertor and then I flip the power switch to the convertor...

For my Bridgeport and Lathe I have a small Rotary Phase Convertor that I spin with a rope... 35 years and no issues.

One of the medical facilities had issues... I was asked to check it out... they had a rotary phase convertor and no one knew it... it was outside and running for years until if failed.

The manager called the power company and was told there is no 3-phase from the utility... then an electrician was called who bid bringing it in for 40k...

I said for 2k you can just replace what you have... boy were they happy... that was maybe 12 years ago...

 

[TMGT]

That's just ridiculous, I was lucky enough that they put 3phase on the pole in front of my house a few years ago, so when I built my new shop I was able to run a 400amp 3phase service to it.

 

[buickanddeere]

Best thing! I bought a BIG Lincoln Welder at an Auction by accident that was only three phase. I built a nice 10HP 600 Volt phase converter. Then got a drill/milling machine. What a pain to stop and start a phase converter. I sold everything 600 volt and bought a Lincoln 220 volt MIG. I don't even know how you would stop and start a rotocon for a compressor.

Does that welder use two or three live lines ?