Phase converter going in

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Righty Tighty

Righty Tighty

Blame it on the dog
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My lathe is a 3 phase machine, as are my pedestal grinder and surface grinder. I had originally planned to run them off of a 6HP rotary transformer, but then things changed.

I found a deal on a rotary screw compressor that I couldn't pass up, also 3 phase. However, it's a 25HP unit. So I found a 30HP rotary phase converter and we're off to the races.

I'm not an electrician, but I've played one on TV, so I feel pretty good about most of the install. I consulted a commercial electrician on the things I wasn't certain on because A) I don't want to burn my shop down and B) I don't want to cook myself like a hot dog.

I felt I'd document the install here in case anyone was interested for their own setup, or if there's anyone who sees a big no-no and has some advice along the way.

oFyFv7BzTuaBA+XaxAI+8w.jpg
 
The converter is a Phoenix Phase Converter and runs off of a bank of capacitors, which will then feed a breaker panel with 3 phase power. It's on a 50 amp circuit and I'll be using AWG 2 wire from the idler motor to the control panel, 2 gauge from the single phase supply to the control panel, also AWG 2 to feed the breaker panel. I understand that 2 gauge is probably overkill for a 50 amp circuit, but that's what it came with so that's what I'm using.

I'll determine the gauge that supplies the branches once I confirm the amperage draw of each machine, and then use an online calculator to figure conduit fill, so I can buy the right size conduit.
 
Righty Tighty said:
The converter is a Phoenix Phase Converter and runs off of a bank of capacitors, which will then feed a breaker panel with 3 phase power. It's on a 50 amp circuit and I'll be using AWG 2 wire from the idler motor to the control panel, 2 gauge from the single phase supply to the control panel, also AWG 2 to feed the breaker panel. I understand that 2 gauge is probably overkill for a 50 amp circuit, but that's what it came with so that's what I'm using.

I'll determine the gauge that supplies the branches once I confirm the amperage draw of each machine, and then use an online calculator to figure conduit fill, so I can buy the right size conduit.
Click to expand...
I am skeptical a 50Amp single phase breaker will supply a convertor for 25hp compressor if I understand what you shared. I don't have any experience directly with rotary compressors and if they might have a soft start nature. I'd guess you are needing closer to a 100amp feed to the convertor to run that size compressor, which btw sounds really neat. This should be covered in some manual online or otherwise. My experience is with a 25hp rotary convertor starting a typical 3Phase 7.5hp compressor, and it grunts upon start up. #2 is always better, but its really IMO just a really big surge on start-up that is the potential issue.
Mine rides on a 4 wheeled car wheel dolly. :D
 
I really appreciate the input. The 50a single phase breaker has kind of always been a concern, even running my single phase machines. I’ve spoken to my landlord and apparently it’s not feasible to upgrade the panel to anything larger.

I agree that it would be wise to consult the manual for the compressor. So far all I’ve got are the specs on the motor badge. It’s a 25 horse, 48 amp motor, no start capacitors that I can see. So, having said all that, I wonder if the 48 amp rating includes the start up amperage?

The electrician I spoke with didn’t seem concerned about it, he was more cautionary about overloading the panel by using multiple machines at once. That’s a non-issue for me since I’m a one man shop and can only use one at a time.

I do appreciate your input and will be looking into it for sure.
 
Let's be clear on a couple things first, both the rotary convertor and the rotary compressor are motors, so be clear which one you are referring to in this discussion. You will from my experience find yourself running the compressor and at least one other item at the same time more than you think. That is not as bad as it sounds. The problem is both starting at the same time, which seems is going to be a concern in your situation. Worst that can happen even if only occasionally, the breaker will trip, and if in the middle of a machining operation that is not ideal.
BTW, install a $30? lightning arrestor in the single phase panel, it's really cheap protection.
BTW a 6hp convertor is woefully inadequate for this task, not sure how I missed that and maybe adequate just for the other machinery, if running two convertors is an better option.
 
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Well, I for one know absolutely nothing about it. Do us a favor though. If you "cook yourself like a hot dog" we want pictures. Video even better.
 
I have serious doubts a 30 HP Rotary Phase Convertor will run a 25 HP compressor... Generally you would want at least double the HP rating due to start up load... Soft start would help...

My lathe is 7.5HP & I run a 15HP RPC..
 
Check the link... The company that sells you convertor suggests a 60HP RPC for a 25HP air compressor... Air compressors far into the very hard load category....

www.phoenixphaseconverters.com

Phase Converters

We offer a large selection of rotary phase converters, run capacitors, electrical transformers, IEC motors, and single phase to three phase converters.
www.phoenixphaseconverters.com www.phoenixphaseconverters.com
 
You are out of my league, (I think I said that wrong, LOL) HP wise, on this one. But I agree with the others as to capacity concerns. All phase converters that are motor driven are quite inefficient. There is a LOT of losses.

Also, high HP 3 phase motors have very different starting loads than do single phase.

One thing I would investigate on the compressor, is using a smaller motor pulley to slow it down some. I would also investigate different unloader options, to maybe allow it to "soft start" under no compression, a way to allow it to spin up to full RPM and get running, then close the unloader. I am not exactly sure how you would do this. Perhaps a solenoid operated unloader, driven by a time delay relay.

You may be aware, that the head operates at VERY high temps, so any unloader "rigs" you need to keep that in mind.

This chart here suggests that a 10hp SINGLE phase motor draws about 50A full load at 230V single phase

www.elliottelectric.com

Elliott Electric Supply - Lower Cost, Quality Electrical Supplies, and Personal Service

Electrical Supplies Distributor. Elliott Electric Supply is your local electric supply house. We Deliver Lower Cost, Quality Products, and Personal Service
www.elliottelectric.com

You will be (if anything) WORSE than that because of converter losses. And remember, that 3 phase motor plate loads are are per phase, aka you have 3 of them. But 3 phase is not 180 or in phase. Three phase is 1/3 of a wave out of phase with each succeeding wave, so this skews the load ratings. But with your proposal you are essentially pulling single phase loading + the inefficiency of whatever converter you have going. In other words, and this is a guess, you need to go by a 25hp SINGLE phase motor rating + the estimated converter losses.

This site suggests about 7A at 230V PER HP of single phase motors

Electrical Motors - Full Load Amps

Full load amps for single and 3-phase 460 volts, 230 volts and 115 volts electric motors.
www.engineeringtoolbox.com www.engineeringtoolbox.com
 
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J-c-c said:
Let's be clear on a couple things first, both the rotary convertor and the rotary compressor are motors, so be clear which one you are referring to in this discussion. You will from my experience find yourself running the compressor and at least one other item at the same time more than you think. That is not as bad as it sounds. The problem is both starting at the same time, which seems is going to be a concern in your situation. Worst that can happen even if only occasionally, the breaker will trip, and if in the middle of a machining operation that is not ideal.
BTW, install a $30? lightning arrestor in the single phase panel, it's really cheap protection.
BTW a 6hp convertor is woefully inadequate for this task, not sure how I missed that and maybe adequate just for the other machinery, if running two convertors is an better option.
Click to expand...
So far, the only things I've been running simultaneously are the compressor and plasma cutter. I don't see any scenario running a lathe and compressor, or surface grinder and compressor, or surface grinder and lathe at the same time.

The 6HP converter was for an individual machine. I decided to upgrade once I acquired the screw compressor.

The main issue here seems to be the compressor, and I can swap motors for a 15HP.
 
Be sure on the comparability of the items. some 3 phase units are 525 volt. my one CK10 is 525 volt and the other is 230 volt. both 3 phase.
 
Max1196 said:
Be sure on the comparability of the items. some 3 phase units are 525 volt. my one CK10 is 525 volt and the other is 230 volt. both 3 phase.
Click to expand...
Many of those types of motors are dual voltage, AKA can be rewired. Check the nameplate
 
1WildRT said:
Check the link... The company that sells you convertor suggests a 60HP RPC for a 25HP air compressor... Air compressors far into the very hard load category....

www.phoenixphaseconverters.com

Phase Converters

We offer a large selection of rotary phase converters, run capacitors, electrical transformers, IEC motors, and single phase to three phase converters.
www.phoenixphaseconverters.com www.phoenixphaseconverters.com
Click to expand...
I've noticed you haven't addressed this yet.... It would be a shame if you bought wiring supplies & got everything hooked up only to find it won't do what you want it to do... I'd suggest getting the compressor close to the power panel and the RPC... Hook everything up and test it before doing a lot of work... BTW I started with a 10 HP RPC for my 7.5 HP lathe... It didn't work & I had to do it over... We all find deals & hope for the best... But throwing money & time at setting this thing up is gonna be a bummer if it doesn't work...
 
1WildRT said:
I've noticed you haven't addressed this yet.... It would be a shame if you bought wiring supplies & got everything hooked up only to find it won't do what you want it to do... I'd suggest getting the compressor close to the power panel and the RPC... Hook everything up and test it before doing a lot of work... BTW I started with a 10 HP RPC for my 7.5 HP lathe... It didn't work & I had to do it over... We all find deals & hope for the best... But throwing money & time at setting this thing up is gonna be a bummer if it doesn't work...
Click to expand...
Sorry about that. I mentioned earlier that I might just swap the motor for a 15 horse motor. However, if air compressors fall into the very hard category, might go 10 HP. The model of screw compressor I have came with options for smaller motors, only downside is you lose CFM.

1WildRT said:
We all find deals & hope for the best
Click to expand...
So true. So very true...
 
67Dart273 said:
One thing I would investigate on the compressor, is using a smaller motor pulley to slow it down some.
Click to expand...
The compressor is a rotary screw compressor -- direct drive from the motor to the unit, so unfortunately there are no pulleys.
 
Well this is just for you, Rusty. I forgot about this old gem. Forgot to disconnect power one time a few years back. Needed to change my britches afterwards.
IMG_3387.JPG
 
67Dart273 said:
You are out of my league, (I think I said that wrong, LOL) HP wise, on this one. But I agree with the others as to capacity concerns. All phase converters that are motor driven are quite inefficient. There is a LOT of losses.

Also, high HP 3 phase motors have very different starting loads than do single phase.

One thing I would investigate on the compressor, is using a smaller motor pulley to slow it down some. I would also investigate different unloader options, to maybe allow it to "soft start" under no compression, a way to allow it to spin up to full RPM and get running, then close the unloader. I am not exactly sure how you would do this. Perhaps a solenoid operated unloader, driven by a time delay relay.

You may be aware, that the head operates at VERY high temps, so any unloader "rigs" you need to keep that in mind.

This chart here suggests that a 10hp SINGLE phase motor draws about 50A full load at 230V single phase

[/URL][/URL][/URL][/URL]

You will be (if anything) WORSE than that because of converter losses. And remember, that 3 phase motor plate loads are are per phase, aka you have 3 of them. But 3 phase is not 180 or in phase. Three phase is 1/3 of a wave out of phase with each succeeding wave, so this skews the load ratings. But with your proposal you are essentially pulling single phase loading + the inefficiency of whatever converter you have going. In other words, and this is a guess, you need to go by a 25hp SINGLE phase motor rating + the estimated converter losses.

This site suggests about 7A at 230V PER HP of single phase motors

[/URL][/URL][/URL][/URL]
Click to expand...
What you are not taking in account
1WildRT said:
I've noticed you haven't addressed this yet.... It would be a shame if you bought wiring supplies & got everything hooked up only to find it won't do what you want it to do... I'd suggest getting the compressor close to the power panel and the RPC... Hook everything up and test it before doing a lot of work... BTW I started with a 10 HP RPC for my 7.5 HP lathe... It didn't work & I had to do it over... We all find deals & hope for the best... But throwing money & time at setting this thing up is gonna be a bummer if it doesn't work...
Click to expand...
That reminds me. Fancy golf courses require irrigation nearly daily in Florida. Post hurricanes they freak out with multi day power outages. I have supplied Cat 450hp 3 phase diesel generators for the 75hp well pumps during the outages, and it was shocking the hit the generator took on well pump start ups.
 
I don't see a problem with running multiple machines with your compressor on that converter, but I've been wrong before. An electronic soft start would help. Only one way to find out..
I run my garage on a 5hp rotary that I built myself and got the leg balance dialed in pretty tight with the caps. I have an unbalanced 3hp rotary for the EMCO lathe and other stuff that is in the basement.
 
J-c-c said:
That was your first mistake we agree, but I usually as a precaution work as if everything is hot anyway.
Click to expand...
That was years ago but yes, I always kill power beforehand. Well, except for that one time......

The compressor issue has been driven home, and I appreciate the input/advice. I'm going to move forward with the converter install and address the compressor situation when it's time. The compressor is only one component and can be changed.
 
RT one thing you might consider, is simply using a smaller, typical 1 1/2-3hp single phase compressor for some of the smaller jobs. It would likely be more efficient overall.

I did not realize it was a screw, which I would guess would lighten the starting load considerably.
 
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