# Wiring my 3 Phase Lathe to my RPC



## erikmannie (Oct 11, 2020)

My 220V, 3 phase lathe is coming in a few days. It is a 5HP machine. I have my 10HP RPC all ready to go.

The good news is that my RPC already has a female outlet (I will post a picture), so all I need to do is connect the wires from my new machine to the male connector (I will post a picture).

Ideally, the machine would come with a male plug already on it. However, I anticipate having to connect the wires to my male plug. As far as I know, maybe the machine will come with no plug or wire.

Understand that I am only asking about the connection from RPC to the lathe. The connection from the wall to the RPC (including consideration of breaker sizes) has already been taken care of.


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## matthewsx (Oct 11, 2020)

Since the lathe isn't going anywhere why not just hardwire it rather than using an extension cord? That way the outlet will be available for anything else that needs it.

John


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## erikmannie (Oct 11, 2020)

Here is the female receptacle on my RPC:


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## benmychree (Oct 11, 2020)

Easy if you have the matching plug, only hitch is possibly needing to reverse wires at the plug to achieve proper rotation direction of the lathe spindle.
I also agree with the above response.  When and if you get another machine that needs 3 phase, it becomes a PITA to constantly have to change plugs.


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## erikmannie (Oct 11, 2020)

matthewsx said:


> Since the lathe isn't going anywhere why not just hardwire it rather than using an extension cord? That way the outlet will be available for anything else that needs it.
> 
> John



The lathe definitely isn’t going anywhere, but I need to keep the RPC receptacle available for plugging a mill into it later.


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## benmychree (Oct 11, 2020)

So, the number on the receptacle needs to match the plug that you will need


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## matthewsx (Oct 11, 2020)

Yep, those are good plugs and Leviton is very proud of them. Plastic conduit and wire won't set you back much, possibly less than the male plug and definitely less than that and any length of insulated 4 conductor wire for an extension cord.

John


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## erikmannie (Oct 11, 2020)

Here is the matching male plug. The company that sold me the RPC sold me this at the same time:


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## erikmannie (Oct 11, 2020)

And here is the wire. This was also part of the single order from American Rotary:


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## erikmannie (Oct 11, 2020)

Maybe I should hire an electrician to decide where to attach each wire. My Dad (who was an electrician) helped me with my 220V welding plugs, but he doesn’t know too much about 3 phase.


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## erikmannie (Oct 11, 2020)

I will post pictures of the terminals on the machine when it comes in a few days.


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## erikmannie (Oct 11, 2020)

Here is a guy doing the same thing on the same machine, starting at the 2:55 mark (and ends at the 6:05 mark):


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## erikmannie (Oct 11, 2020)

From watching the above video, the machine comes with a cord already wired to the machine. 

This being the case, I don’t know why I bought a length of cord from American Rotary. I will have the option of using the factory cord or the length that I bought from American Rotary.


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## erikmannie (Oct 11, 2020)

I gather that the 3 phase has ground, x, y and z.

It looks like green may be ground, and the red, white and black are the x, y and z are the 3 legs.

In another thread, a few people said something to the effect of not attaching the manufactured leg to (?). I understand that, while 2 of the legs may be interchangeable, the manufactured leg must be attached to the proper terminal.

Maybe I could look inside the RPC and match the colors for each male & female terminal (red to red, white to white, etc.).

I won’t be electrocuting myself because the RPC isn’t plugged in, but I want to avoid frying either my new RPC or lathe.


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## Winegrower (Oct 11, 2020)

The nice thing is that if you get the ground correct, the others don't really matter.   If the spindle rotates the wrong way, switch any two.
And the ground is easy, it's the green wire.


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## erikmannie (Oct 11, 2020)

Winegrower said:


> The nice thing is that if you get the ground correct, the others don't really matter.   If the spindle rotates the wrong way, switch any two.
> And the ground is easy, it's the green wire.



This does sound like an easy job! I just want to fish out this question of not attaching the manufactured leg to the (?). I will look up that info now...


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## erikmannie (Oct 11, 2020)

Here it is. @mksj said:

“The RPC is sweet, it is a 50A socket for the input. One thing that is very important, is that two legs of the 240VAC are pass through, these must be attached to the transformer legs on the lathe/mill/etc. The wild leg (manufactured/generated leg) should not be connected to a control transformer or circuity.”


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## erikmannie (Oct 11, 2020)

Apparently, if I attach the “wild leg (manufactured/generated leg)...to a control transformer or circuity”, the machine can run (1) rough, and (2) sub-optimally.


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## erikmannie (Oct 11, 2020)

In this YouTube video, the gentleman talks about x, y and z at the 1:45 mark:






In the video, he says:
green for ground,
black for x
white for y
red for z (and z is the wild leg)


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## NCjeeper (Oct 11, 2020)

Winegrower said:


> The nice thing is that if you get the ground correct, the others don't really matter.   If the spindle rotates the wrong way, switch any two.
> And the ground is easy, it's the green wire.


Yep. Easy peasy.


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## erikmannie (Oct 11, 2020)

This is a pertinent, basic video that I find helpful:


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## matthewsx (Oct 11, 2020)

Yeah, it's not that complex. Three phase is just the three wires, switch any two to change direction, ground is ground. The 220V single phase is also simple, two hot legs, one neutral and one ground.

But, sorry to tell you you're going to have to send that plug back. It's an L15-20, similar but not the same as the L15-30 notice the tang points out instead of towards the center.

I'm still for hard-wiring the lathe though. In addition to saving the flexible cords for stuff that needs to move around you get the advantage of running your conductors in conduit which will protect them from cuts and burns.

John


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## erikmannie (Oct 11, 2020)

That is ridiculous that they sent me the wrong male and female plugs. I did all of that in one order!


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## matthewsx (Oct 11, 2020)

They are easy to get mixed up, hopefully they'll just send you the right one and you can use the other on a generator.

John


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## erikmannie (Oct 11, 2020)

matthewsx said:


> Yeah, it's not that complex. Three phase is just the three wires, switch any two to change direction, ground is ground. The 220V single phase is also simple, two hot legs, one neutral and one ground.
> 
> But, sorry to tell you you're going to have to send that plug back. It's an L15-20, similar but not the same as the L15-30 notice the tang points out instead of towards the center.
> 
> ...



That was a really good catch on your part to notice that the male and female plugs can’t connect together. I just called American Rotary, and they are going to send out the proper replacement and a return label for the wrong male plug. I don’t think that there is a charge for that.

I have had this RPC for over 3 months, just sitting here waiting for my new lathe.


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## matthewsx (Oct 11, 2020)

Ask me how I know this  

John


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## Papa Charlie (Oct 11, 2020)

erikmannie said:


> Here is the matching male plug. The company that sold me the RPC sold me this at the same time:
> 
> View attachment 340155



That doesn't look right. The ground lug should have the kicked up leg pointing in towards the center like you receptacle, the one in the image above is pointing outward.


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## mksj (Oct 11, 2020)

As mentioned, the plug is a 30A 4 prong. According to the AMP RPC manual L1 and L2 are the line voltage and L3 is the manufactured leg. The ground is typically the dog legged prong on twist locks, it should also be marked green on the screw. You will need to check with American Rotary as to which prong on the plug in the AMP is the wild leg (I am assuming this is the Z). I would suggest that for L1 you use the black wire, L2 use the red wire and L3 (wild leg) you use the white wire. Typical convention is to wrap a different colored tape (around the white wire to denote it is not a neutral, I will often use some, black, red or brown tape) but doesn't matter in this case.  At the lathe you will need to connect the wires to the terminals labeled R, S, and T. The lathe power transformer should have the wires labeled, in the last RL lathe I did an install on, the transformer terminals were labeled R and T (see below) so the wild leg should not be connect to R or T. If you motor is running the wrong direction, then flip the R and T wires at the power connection terminal strip. Be sure ALL POWER IS OFF. You can connect bare wire to the RST connection terminals but I prefer crimped with a locking spade. The crimps must be correctly sized and crimped properly, so if you have an electrician friend maybe have him/her look it over or give you a hand.
R = Black Wire L1
S = White wire L3
T = Red Wire L2

GREEN, GREEN/YELLOW is always ground connect to the "E" terminal.


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## erikmannie (Oct 11, 2020)

mksj said:


> As mentioned, the plug is a 30A 4 prong. According to the AMP RPC manual L1 and L2 are the line voltage and L3 is the manufactured leg. The ground is typically the dog legged prong on twist locks, it should also be marked green on the screw. You will need to check with American Rotary as to which prong on the plug in the AMP is the wild leg (I am assuming this is the Z). I would suggest that for L1 you use the black wire, L2 use the red wire and L3 (wild leg) you use the white wire. Typical convention is to wrap a different colored tape (around the white wire to denote it is not a neutral, I will often use some, black, red or brown tape) but doesn't matter in this case.  At the lathe you will need to connect the wires to the terminals labeled R, S, and T. The lathe power transformer should have the wires labeled, in the last RL lathe I did an install on, the transformer terminals were labeled R and T (see below) so the wild leg should not be connect to R or T. If you motor is running the wrong direction, then flip the R and T wires at the power connection terminal strip. Be sure ALL POWER IS OFF. You can connect bare wire to the RST connection terminals but I prefer crimped with a locking spade. The crimps must be correctly sized and crimped properly, so if you have an electrician friend maybe have him/her look it over or give you a hand.
> R = Black Wire L1
> S = White wire L3
> T = Red Wire L2
> ...



I very much appreciate your comprehensive and tremendously helpful response.


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## erikmannie (Oct 11, 2020)

A good friend of mine weighed in via email. I have paraphrased most of his points here:

American Rotary will be able to tell me which female prong comes from the manufactured leg. The corresponding male prong should go to the motor in the lathe and NOT to any other circuits or transformers (with the understanding that it will pass through some motor switching). This is because the voltage & phasing of the wild lead is variable (and thus less stable than the other two hot leads).

The leads which are not wild are more desirable for servicing controls and electronics.

He is not sure of any risks associated with attaching the wild lead to controls, circuits and/or transformers, and he recommends that I check in with both American Rotary and Precision Matthews.

The voltage of the manufactured leg is generated by the motor and capacitors, etc. in the RPC.

I hope that I was accurate in paraphrasing him.


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## erikmannie (Oct 11, 2020)

In about 3 days, I will post detailed pictures of where the 4 wires are proposed to attach to the new machine.

I will also post what American Rotary and Precision Matthews had to say.


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## ThinWoodsman (Oct 12, 2020)

Just to throw another idea out there, I ran my (also American Rotary) RPC to a 3-phase breaker box, and added a breaker for the mill and one for the lathe. Cannot remember if the box allowed for 3 or 4 connections, but I have at least one spare. The machines did not come with cords, and are wired directly to the breakers (via conduit).


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## erikmannie (Oct 13, 2020)

The lathe came. The picture below is of the electrical panel in my PM-1660TL. The lathe does not come with a cord or plug.

I called American Rotary, and they said that they installed the wrong female receptacle in the rotary phase converter. They meant to put in a 20A, and they put in a 30A. They are sending me a 20A (female) receptacle for the RPC, and I will install that.


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## mksj (Oct 13, 2020)

So on your machine R and S are used for the transformer, so these would be L1 and L2. Wild leg would be L3 and connect to the T terminal. You could leave the 30A 3 phase socket in the RPC and just wire it in. The stock motor is ~14A 3 phase. These machines do not come with power cords.
X -> R = Black Wire L1
Y -> S = Red Wire L2
Z -> T = White Wire L3 (Wild Leg) Would mark this with a black tape band.


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## matthewsx (Oct 13, 2020)

Yeah, I wouldn't change the receptacle on your RPC. Assuming you have knockouts in both the lathe and RPC I'd just run conduit and pull individual conductors. Leave the outlet for something that will live on wheels.

John


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## erikmannie (Oct 13, 2020)

mksj said:


> So on your machine R and S are used for the transformer, so these would be L1 and L2. Wild leg would be L3 and connect to the T terminal. You could leave the 30A 3 phase socket in the RPC and just wire it in. The stock motor is ~14A 3 phase. These machines do not come with power cords.
> X -> R = Black Wire L1
> Y -> S = Red Wire L2
> Z -> T = White Wire L3 (Wild Leg) Would mark this with a black tape band.



I do believe that there is enough information for me to get it wired. My new female receptacle arrives in approximately a week.

Thank you very much for this information. I am pretty sure that I could not have gotten to going without that.


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## erikmannie (Oct 13, 2020)

matthewsx said:


> Yeah, I wouldn't change the receptacle on your RPC. Assuming you have knockouts in both the lathe and RPC I'd just run conduit and pull individual conductors. Leave the outlet for something that will live on wheels.
> 
> John



I do have knockouts on the RPC.

The way my shop is set up, I need to be able to move the RPC because I am entirely compulsive about sweeping the floor.

There are only 5 things in my entire shop that are not on wheels; I have spent a lot of money on carts and casters  so that I can sweep the floor.

I used to work in MIG shop where the guy had a lot of dust and even mud. I quit because of that. Dust and welding are a bad mix.


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## erikmannie (Oct 13, 2020)

I have a 20A breaker in my RPC. This arose from the discussions on the motor specifications given to American Rotary back when I bought the AMP-10 RPC (in July).

When I discussed the aforementioned male/female mismatch issue with American Rotary (this morning), they advocated for running a 20A receptacle & plug.

I already have a 20A receptacle on the way. As it stands now, I am going to install that in my RPC. I already have a return label for the original 30A receptacle.

20A connectors ought to be good enough, right?


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## erikmannie (Oct 13, 2020)

Here are screenshots of the electrical component list:


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## pontiac428 (Oct 13, 2020)

Erik, the 20A breaker supports the 20A receptacle.  To get the whole 10 hp from your RPC, you'd use a 60A.  T should be the wild leg, it only goes to the spindle motor.  If your motor runs backwards, swap R and S.  Otherwise, that's it, 3 wires and a ground.

I think @matthewsx makes a good point about running a pigtail (with strain relief) from your RPC with the right receptacle rather than swapping the one that is mounted- just a preference that will keep your RPC available for any other 3 ph. equipment that happens to show up.


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## matthewsx (Oct 13, 2020)

Well, I can't read half of that but if there is a 50 amp main fuse you should be able to pull 50 amps from it. My preference would be to run a 3 phase sub panel off the main output and wire loads to that with appropriate over-current protection for each attached load. If I had a "floor mounted" unit and wanted to sweep behind it I would build a small shelf attached to the wall to raise the motor up so I could clean. BTW, I'm with you on being able to clean behind anything in the shop, good housekeeping is critical to safety.

So, back to what you have and how to deal with it. My preference would not be to change the outlet, if you want it to protect 30 amp loads you can just change the breaker. As is, it will provide a safety margin of 10 amps given the 20 amp breaker installed, this shouldn't be a problem because the breaker will trip at a load below what the receptacle can handle. You can wire the circuit for your lathe directly off the same breaker and it should only trip if you have a short, or plug another load into the receptacle and run both at the same time exceeding 20 amps. This is unlikely since you are the only one operating equipment in your shop and probably can't run two machines at once.

There's nothing wrong with having multiple loads connected to one breaker, your house is wired like this and so is almost every other building out there. Wire sizing isn't a mystery either, here's one calculator 





__





						Wire Size Calculator
					





					www.paigewire.com
				




According to this you can run 14 gauge wire for a three phase 20 amp load 20 feet away, that's 80 ft of wire. 500 ft of 14 gauge is ~$40 at Home Depot, or ~$60 for 12 gauge if you want to oversize, you can buy it by the foot but getting the spool means you don't have to go back if you underestimate how much you need. A 10' stick of PVC schedule 40 conduit is $3.15, I'm not gonna price out the adapters but they won't be that much. 

Bottom line, less than a hundred bucks will let you do this right and hardwire your new machine back to the RPC. You probably can't run overhead because of how close you are to the garage door but conduit on the floor will probably be less of a trip hazard than multi-strand flexible cord. 

This is just how I would do it, I'm not an electrician (well, marine electrical certified) but I've done plenty of wiring in my own home and wouldn't be writing this if I wasn't confident of what I'm saying. You're gonna have to open up the RPC distribution box either way so why not save yourself the hassle of having to do it again when you need to hook up your new mill with a three phase extension cord?


JMHO,


John


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## erikmannie (Oct 14, 2020)

American Rotary sent me a link to this informative video:


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## Eddyde (Oct 14, 2020)

matthewsx said:


> According to this you can run 14 gauge wire for a three phase 20 amp load 20 feet away


However, the NEC requires 12 gauge minimum wire on a 20 amp circuit. And I believe on any motor circuit above ¼ hp.


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