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3 phase the easy way

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Blog entry by MedicKen posted 647 days ago 3277 reads 0 times favorited 13 comments Add to Favorites Watch

As most of you know I love the old machines. In fact my entire shop is vintage. The table saw is a 1952 Oliver 232, jointer a 1925-28 Crescent 8”, drill press is 1977 Powermatic 1150A, planer 1958 Delta 13” 22-101 and a 1968 Delta 14” bandsaw. All but the bandsaw and jointer are 3 phase machines. I would like to have a larger bandsaw some day and have my eyes open for a nice Tannewitz 30” that would fit the bill really nicely. But for now the 14” will have to do.
I have been running the 3 phase machines utilizing VFD’s, and while they do a fine job of converting single phase to 3 phase I was getting tired of shelling out $100-200 dollars every time I got a new machine. So, I decided to take the plunge and install a rotary phase converter. I will however, keep the drill press running with the VFD. Variable speed is just so nice to have with it and not having to swap belt locations on the sheaves is a time saver.
My quest for the RPC began about 3 years ago. I found a nice old cast iron Westinghouse 10hp 3 phase motor that could use as an idler to generate the 3rd phase. Best part of it it was only $60. Its solid cast with about 60# of copper in it, total weight pushing 130#.

I did pull the sprocket from the shaft and tore into the motor. It was full of dirt, spider webs, yellow jacket nests and appeared to have been in a flood. The stator was lightly rusted but the windings all looked to be in good shape. So, I ordered bearings and cleaned it up a little. About $20 for sealed Nachi bearings.
After some conversations with others who have RPC’s and LJ’s own TopamaxSurvivor, I decided that the new converter would require a 60A service. Luckily when I had the house built I had the foresight to upgrade the main service panel to 200A, it gave me enough room to add another 60A breaker. All that was left now was to start acquiring the necessary supplies to install it.
There are a couple of different options when it comes to installing a converter of this size. 1) you can purchase a ready made unit or 2) build your own. I chose not to build my own as my electrical knowledge is just enough to be dangerous and I did not feel comfortable with the construction and it would actually cost more to build. What I finally decided on was a pre-manufactured panel from American Rotary. They can be found here. However I must warn you, the panel only is not available directly from the their website. I found this to be a little odd and called to ask why. Their response was they have better sales on Ebay. So, I patiently waited for the one I had chosen to go on sale, which it did about 3 days later, and rest we shall say is history.
What I selected is a 10hp panel that is CNC ready. I will not really be needing the CNC balance capability of the converter but hey it was on sale and as I told the LOML, it was on sale and I saved you money.
I took a few days while waiting for parts to arrive for the Delta planer I am restoring went about installing the RPC. I started by pulling a few things off the wall where it would be located and removing a 1/2 sheet of drywall. The main service panel for the house is located on the same wall as the new RPC will be and only about 6’ away. It made pulling wire much easier and cheaper as well. 4ga wire is NOT cheap, nor easy to pull. I got the wire pulled and replaced the drywall. I did not want to use the breaker that I would be installing as a switch to power the panel so I purchased a 60A 2 pole 240V disconnect and ran the wire from the main into the disconnect.
Next was to mount the RPC panel itself. I had decided that I wanted it mounted fairly high on the wall to keep smaller hands away. With the panel mounted I went about wiring it. 4ga wire in 1” conduit is tight but doable.
With the majority of the wiring done I tunred my attention back to the motor and its placement. I wanted to place it in a location that would protect the rotating shaft. I built a small stand to get it up off the floor and tucked it back in between the wall and the garage door with the shaft in the corner.

Once the motor was mounted I set to wiring it. 10ga wire from the panel to motor in some water tight conduit and 30 minutes later I was cleaning up. Now came the time to fire it up and see how I did. Luckily my neighbor is a retired batallion chief with the local county fire dept if all went to hell I knew where to run..LOL

I went outside and turned on the main breaker feeding the disconnect, no tripping, arcing or humming….cool. Now inside to the disconnect, I threw the handle up and same result. I am at this point keeping my fingers crossed that the panel will start the motor and my efforts will have paid off. I hesitantly pushed the start switch and the idler sprung to life!! Very cool! The small stand does add to the noise of the motor a little. Kinda like a bass reflex speaker. Even though it is only 6” off the floor is does amplify the noise somewhat, but not so loud that you cannot stand next to it while its running and hod a normal conversation. But loud enough that I will never forget to turn if off at the end of the day.

All that is left is to install an outlet on the wall so I can now plug in my 3phase machines. It is not the best looking installation cosmetically speaking but it will get the job done. The motor I chose for the idler needs room to ventilate for cooling. It is an open design with no fan for cooling. I will be adding a piece of metal screening over the shaft to keep small scraps and hands away from it while its running. But for the most part its up and running. I also need to measure the balance between the legs and see how well balanced they are. I am also considering adding some small digital meters on the panel face that will read out the voltage of each individual leg.

I am now capable of running up to 7.5hp of 3 phase equipment and looking forward to getting it all finished. For those thinking it will cost an arm and leg for something like this I am here to tell you its really not too bad. The panel was $350 with free shipping. Bearings under $20. Wire, the expensive parts, was about $100. I do still have to mount the outlet which will cost about another $100-150. I know that seems high but it will also require rewiring each machine with a mag starter, power cord and plug.

Here is short video of not so good quality, but you get the picture.

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com



13 comments so far

View Robb's profile

Robb

660 posts in 2567 days


#1 posted 647 days ago

Nice overview. I’ve often looked longingly at the 3-phase beauties of craigslist. Maybe one day, I’ll follow in your footsteps.

-- Robb

View JimDaddyO's profile

JimDaddyO

286 posts in 1712 days


#2 posted 647 days ago

Good job, congrats. A couple of layers of owens corning 703 fiberglass insulation and a piece of plywood would make a nice base for it to sit on that would decouple it from the floor and help with the noise issue.

-- I still have all my fingers

View John Ormsby's profile

John Ormsby

1279 posts in 2370 days


#3 posted 647 days ago

Congrats Ken on making a Rotary Phase Converter. I had the good fortune to find a Kay Converter for a very good price some years ago. It will run three 7.5 HP motors if they are started one at a time.
One thing to test is the third leg with the existing 2 legs and make sure the voltages are within 1 volt of each other. You do not want much variation on the voltages. Especially if a machine has any electronic controls boards such as electronic auto braking, etc.
I ended up installing a Buck/Boost transformer to balance out the third leg from the converter.

-- Oldworld, Fair Oaks, Ca

View MedicKen's profile

MedicKen

1599 posts in 2095 days


#4 posted 647 days ago

@John…..I have not yet had a chance to test the converter for balance. That is most definitely on the list of to do’s.

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View blackcherry's profile

blackcherry

3156 posts in 2456 days


#5 posted 647 days ago

You have been crown “King Tool Gloat” and this post suck royally…lol and by the way here your new old band saw lol……http://chicago.craigslist.org/nwc/tls/3399581478.html ....BC

View MedicKen's profile

MedicKen

1599 posts in 2095 days


#6 posted 646 days ago

That is a nice saw but not what I am looking for. Being its a 36” I dont have the ceiling height to accommodate it. That is why I want the 30” and it actually has the same resaw capacity as the 36”

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View MedicKen's profile

MedicKen

1599 posts in 2095 days


#7 posted 638 days ago

I got lucky and found a guy selling some NOS twist lock receptacles on the local CL. He had 7 boxes of 10 and they were factory sealed. He was asking $3 a piece for them. I did not even try to knock down the price as new they are $30ea. So, I bought 20 of them. I have also located 3 of the twist lock plugs on ebay for $7, won the auction and am awaiting their arrival. All that is left now is to locate a good deal on some 10 or 12ga SO cord and call it done

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View MedicKen's profile

MedicKen

1599 posts in 2095 days


#8 posted 628 days ago

I finished the install a few days ago. All that was left was to wire up an outlet. I left a little extra “play” in the conduit for future use. I was able to get the receptacle and 3 plugs off ebay for about 10 cents on the dollar. 3phase parts are not cheap.

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View John Ormsby's profile

John Ormsby

1279 posts in 2370 days


#9 posted 628 days ago

Looking good Ken. Looks like you just have one wire to protect coming out of the wall?

Are the final outlets 30 amps each to run 7 1/2 hp motors or are you using the full 60 amps in one outlet?

I have 60 amps powering up my converter and was using only one 30 amp outlet. I am now going to add a second 30 amp outlet to power up another machine with 7 1/2 motors.

Am trying to figure out the easiest way to ad the second outlet.

-- Oldworld, Fair Oaks, Ca

View MedicKen's profile

MedicKen

1599 posts in 2095 days


#10 posted 628 days ago

The outlet is 30A. I am thinking for now I am gonna leave the feed wire, the romex, as is for now. I should have run it in conduit when I pulled it but chose not to.

If I run a second outlet, the box I have has an opening available on the end and I can pig tail off the existing one for another. I dont plan on running more than one machine at a time anyway.

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View MedicKen's profile

MedicKen

1599 posts in 2095 days


#11 posted 623 days ago

I spent about an hour yesterday mounting a manual motor starter to my Oliver 232 and disassembling the VFD I had been running the saw with. It was the best shop time I have spent in a few years. I got the starter mounted, an old Allen Bradley 609 with new heaters for overload protection of the motor. I wired the motor to it and made a trip to the local big box store and came home with 15’ of 12/4SO cord. I wired the SO into the starter and added an L15-30 twist lock plug on the end. Then came the time of hoping I had done it all right. I plugged the cord in, turned on the power to the RPC and turned the converter on. The converter spun up so I went to the saw and hit the start switch. WHAM!! The saw spun up to 3600rpm and sounded like an jet taking off, its friggin awesome!! I love have true 3 phase in the shop. I forgot how loud the saw is, it actually drowns out the phase converter. Now on the finish the planer and jointer so I can start making sawdust again instead of wiping oil, grease, paint etc off everything. I have soooo many projects to do. I am really looking forward to working with wood again.

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View b2rtch's profile

b2rtch

4318 posts in 1682 days


#12 posted 237 days ago

Can you explain how the whole thing works.
Why do you need an electrical motor to start with?
Thank YOU.

-- Bert

View EEngineer's profile

EEngineer

890 posts in 2247 days


#13 posted 236 days ago

Let’s give this a shot…

Every electric motor is also a generator. In fact, the “back-EMF” generated by the motor running at speed is primarily what limits motor current when the motor is up to rated speed.

You can run a 3-phase motor on single-phase by powering only two of the windings. You don’t get rated HP out of it and you have to “help” the motor to start in the proper direction but it will run like this. The generator characteristic of the motor will power the undriven phase.

That is it in a nutshell. Googling “rotary phase converter” will fill in the details.

-- "Find out what you cannot do and then go do it!"

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