Single Phase vs. Three Phase for new tools

[Michael Koons]

I've been active on the forum lately as I'm in the process of buying a new J/P and bandsaw and due to unforeseen circumstances, I continue to have more questions.

I have the option of getting a single phase 4HP J/P or the 3 phase 6HP version. I've researched RPC's and it looks like I can get a 10HP RPC for around $1000 and it looks like installation is pretty straight forward. Do you guys agree that adding a phase converter is no big deal?

The reason I need to know is because if I go 3 phase, I get some options opened up to me. For example, I can get an electric lift on the planer table on the 3 HP version. Hand crank on the 1 HP version. For those of you with experience with the 3ph and 1ph options, do you have thoughts on which is the better direction to go? I imagine that 1ph 4HP is more than enough power for my needs but is the added HP in 3ph worth going that way? I'm interested in anyone's thoughts who may have gone through the same decision process.

As always, thanks!

[Mike Henderson]

If you have 3 phase electrical service to your location, then definitely go 3 phase. If you have to generate 3 phase, I would probably choose to have single phase motors rather than go through the space, cost, and electrical loss of generating it from single phase.

But I was going to generate 3 phase, I would do it with a VFD.

Mike

[Matt Day]

But I was going to generate 3 phase, I would do it with a VFD.

Mike

This.

If he had three phase already, it would be a no brainer.

$1000 sound high for an RPC. A quick look at factorymation and it looks like a 7.5hp VFD is under $500.

[Howard Acheson]

Do you have 3 phase power to a pole close to you and/or is you shop already wired for 3 phase?

What do you perceive to be the benefits to 3 phase?

[John Lanciani]

If I had the money to spend I'd be looking at a Phase Perfect digital converter. http://phaseperfect.com lots of upside, only real negative is cost.

[fRED mCnEILL]

I have a 3 ph table saw with 5HP motor and have a RPC. I bought the saw at an auction and didn't realize it was 3 ph.So I was able to find a cheap rpc. This was 15 years ago and the rcp has worked well although I did have a couple of problems with switches.
While it works fine it is a pain in the butt as to saw I need to turn on the rcp and then the saw. Same with turning it off. I could leave the rcp running all the time but that is wasting electricity and creating some additional noise.
My understanding is the only reason for 3 ph. is cheaper power although when you get into bigger motors 3 ph may be the only kind you can get. Using a RCP just adds another level of complexity.
I recently bought a used compressor that had a 3 ph. motor. I couldn't figure out how to connect the 3 ph wiring so tried a single phase motor.Worked perfectly.

If I had a choice I would not go 3 ph.

[David Kumm]

once you go three phase you will never go back. Opens up more choices, better machines especially on the used market, larger motors, fewer problems. VFD's are great for a few machines, but if you have a shop full, and RPC or better yet, a Phase Perfect, is the way to go. Dave

[Jesse Busenitz]

once you go three phase you will never go back. Opens up more choices, better machines especially on the used market, larger motors, fewer problems. VFD's are great for a few machines, but if you have a shop full, and RPC or better yet, a Phase Perfect, is the way to go. Dave

+1 I just moved shop and upgrade to some 3 phase machines, and I found a like new 15 hp RPC for 350$ and installed a 3phs load center. It was very simple to wire once I read the instructions Having 3 phs opens up the doors for some real deals on machines that nobody wants to touch.

[Peter Quinn]

I went RPC, cost was around $1K from American rotary, simple to install and use. If you want to power a single machine a VFD may be the way to go, I have several different machines that run 3 phase, I run a feeder and shaper together, etc, so the VFD was not my preferred option. Seems maybe the VFD's have dropped in price lately? Used to be over 5HP got pretty expensive quick. Even so buy three machines and put a VFD on each, suddenly the RPC looks cost effective. Phase perfect is perfect except the cost, great if cost is no object, or you really need power that good such as for CNC operation. If its a machine you start and stop frequently like a drill press the VFD seems a better option than a RPC due to noise, cost of generating unused power (though they don't draw a tremendous amount at idle), just easier than starting and stopping the RPC. But for a planer, shaper, etc that in my case I generally run a batch of something, so start it, use it, turn it off for extended periods, the RPC works well.

As far as the convenience, nothing beats a power drive table on a planer, would sure make a combo more attractive than cranking all the way up and all the way down as required to change over on some models.

[Larry Copas]

Sooner or later you will want/need 3 phase so you might as well do it up front and save a lot of jockeying around along with money. I have a RPC and use it all the time. The only drawback is the noise and to a lesser extent turning it on/off. I should have located it some place where I couldn't hear it.

I also have 3 VFD's. I use them only on machines that will benefit from variable speed. In my case its a Bridgeport milling machine, bandsaw, and lathe. I would guess the life span might be similar to TV's or any other solid state device. Above 3 horsepower they are cost prohibitive for me to use.

[Keith Hankins]

I've been active on the forum lately as I'm in the process of buying a new J/P and bandsaw and due to unforeseen circumstances, I continue to have more questions.

I have the option of getting a single phase 4HP J/P or the 3 phase 6HP version. I've researched RPC's and it looks like I can get a 10HP RPC for around $1000 and it looks like installation is pretty straight forward. Do you guys agree that adding a phase converter is no big deal?

The reason I need to know is because if I go 3 phase, I get some options opened up to me. For example, I can get an electric lift on the planer table on the 3 HP version. Hand crank on the 1 HP version. For those of you with experience with the 3ph and 1ph options, do you have thoughts on which is the better direction to go? I imagine that 1ph 4HP is more than enough power for my needs but is the added HP in 3ph worth going that way? I'm interested in anyone's thoughts who may have gone through the same decision process.

As always, thanks!

I've been using 3 phase for a while. If you only will have one tool then a vfd can be a cheaper option but I wanted to be able to handle multiple tools. I went with a 10hp RPC from American Rotary. Great group to work with and made in America if thats important to you at all. I like the older tools and they are cheaper and made 10 better than new(IMO).

if it wer me, I'd def go the 6hp route and install the RPC. There are plans out there to build them but I decided I wanted a supported unit so Amer rotary was a good choice. Mine came with a baldor idler motor to generate the 3rd leg. It's quiet and works like a charm. Knowing what I know now, only thing it would do diff is maybe buy a cheaper idler motor instead of a new one to save a little money. you will be surprised how cheap you can pick up 3 phase motors up on CL or ebay. I picked up a 2hp baldor for 70 bucks because someone bought it not know it was 3 phase.

Good luck if you have any questions let me know. BTW AR puts on sales all the time.

[Mike Schuch]

I love my 3 phase tools! By far their biggest advantage is that I paid about 1/3 what the comparable 1 phase tools would have cost. Not everyone knows about phase converters or VFD's and fewer yet want to mess with them. 3 phase tools are great when it comes to resale... if you are buying the used equipment!

[Michael Koons]

Thank you for all the replies. In all my reading, it seems not all RPC's are alike. I've read that on most RPC's, the 3rd leg will fall off under full load. It seems like only the Kay Industries RPC's maintain balanced power and that their RPC is rated for the HP of the actual 3ph tool you're running. Is this everyone else's experience? I'm guessing the way to get around this is to get a higher rated RPC from one of the "other" suppliers.

[David Kumm]

Kay and Arco rate their converters by the size motor they will start. Most others need to be uprated 1.5-2X depending on how hard starting the motor is. All will provide a fairly balanced voltage once under load and you can buy most all with additional balancing if you need that for the electronics. Quality of the motor is a primary difference. Some use a Baldor, some are Asian, some are steel frame, some are cast iron. Some will run a larger frame motor than others. Do some reading and talking to a few companies. You will find similarities but also some differences. Ask about the motor quality and the quality of the caps and components. There are different price levels of the internals as well. Dave

[Mike Schuch]

Thank you for all the replies. In all my reading, it seems not all RPC's are alike. I've read that on most RPC's, the 3rd leg will fall off under full load. It seems like only the Kay Industries RPC's maintain balanced power and that their RPC is rated for the HP of the actual 3ph tool you're running. Is this everyone else's experience? I'm guessing the way to get around this is to get a higher rated RPC from one of the "other" suppliers.

From what I can tell when I built my 10hp RPC about 20 years ago there are 3 basic implementations of RPC's.

1) Big idler motor started by a smaller pony motor. The pony motor mechanically disengages once the idler motor is up to speed. The generated leg isn't balanced to the other 2 live legs.

2) Big idler motor started with capacitors. The generated leg isn't balanced to the other 2 live legs.

3) Big idler motor started with capacitors and run capacitors used to balance the 3rd generated leg. This is the design I used and the current on the third leg stays balanced with the other 2 legs when I am starting my big 7.5hp radial arm saw.

I think you will find all 3 designs to be effective for running 3 ph machinery and your worry about the third leg fall out under full load is more marketing hype than anything you really need to worry about.