need help hooking up three phase mill

If I'm not mistaken, that *is* a 208/220/240 volt plug, it's not something that someone has screwed around with. Female receptacles are available to match your plug. They're made that way so some fool doesn't plug 120 volt appliances into them.

Harold

that sounds like a 220V plug, contrary to what you say.

yes.

can you ask the seller? People do the weirdest things with wiring.

I think it could be either a 120 volt 20 amp plug or a 240 volt 20 amp plug. They look very similar. But one has the right blade rotated and the other has the left blade rotated..

Dan

Ah... I didn't know both existed! I could have easily confused it. I'll look again.

That plug is intended to be used for 120VAC, and the blades are in a different orientation so that it can only be inserted into a 120VAC 20A rated receptacle (or power cord end connector). The sideways-blade plug is to prevent a 20A appliance from being plugged into a common 15A rated receptacle.

A 20A rated 120V receptacle has a hot blade slot that is sideways-T-shaped. This will allow more common less-than-20A plugs to be used with it, or the sideways-bladed 20A plug.

Depending upon the current demand of the converter and motor, you may want to choose a more versatile 240VAC receptacle and plug. One such style is the type where the blade slots are both sideways (flat, in line, horizontally opposed).

Your best option is choose the properly rated 240VAC receptacle, based upon the NEC recommended style and current rating for the maximum safe current rating of the new circuit you install. You may have, or get more 240V equipment in the future, and having standardized/common connections is best, as well as more convenient.

WB ..........

Thanks for that, Dan. I wasn't aware.

Harold

Here's a good reference on NEMA plug and outlet configuration from Leviton:

-Bill Fill Olympia, WA

The two horsepower motor on my Bridgeport mill draws 6 amps at 220 volts according to the nameplate. I don't know what size motor your mill has, it could be 5 hp. But it seems like a 40 amp breaker might be a little high. ERS

Way cool, Bill.

Thanks.

Harold

Hmmm... No 40amp configurations?

Breakers protect the wire not the machine. That means I can draw a max of 40 amps through the circuit without overheating the wire.

After I posted the above I thought about that. When I wired my shop I put each machine on a separate circuit and the breakers protect the machines. The wire is large enough that the breakers protecting the machines are smaller than the breakers would be to protect the wires. ERS

I suggest that you know the dimensions of the blade spacing on your plugs/sockets when you go shopping. I was going to pick up a plug and socket to make an extension cord for my welder, 50amp 240v. That's one big blade, one small blade and common, kinda like an oversized 110v configuration. Ended up at Home Depot and grabbed a plug and socket and attempted to put them together. Spacings were different!!!! I ended up grabbing the manager of the electrical section and showed him. Blank stare. No idea what to do about it. I thanked him for his time, suggested that he call the manufacturer and ask them how it was supposed to work, and left. Wish I could recall the brand.

It's hardly his fault.

He stocks the plugs and sockets that sell the best. You can bet that he'd have something to fit your dryer or electric stove. I'd lop off the connector on your welder and throw it away and fit connectors that are readily available.

How is the breaker protecting the machine?

Beats me. I just used the breakers suggested by the manufacturer. Maybe they just prevent too much smoke coming out of the motor housing. Actually, I think that's exactly what they are for. If the motor draws too much current, say from an overload, the breaker pops. On my big mill with contactors there are heaters that open the contactors if too much current is drawn. I did pop the breakers once when I lost a leg of the three phase. ERS

I really don't think that is a good way to do it. You're only going to be able to find breakers like 15,20,30... Then you'd have to hope that the machine would draw something like 19 amps for a 20 amp breaker to protect it.

I incorrecly identified "sideways" blade position as the hot/line terminal in my earlier reply.

It is the Neutral terminal in the 120VAC 20A plugs and receptacles.

Hopefully, since the terminals are color coded, this mistake won't cause anyone to connect the leads incorrectly.

sideways-T-shaped.

WB ..............

Most of the NEMA connectors actually *have* the designation molded into them. It'll probably say right on the plug.

Jim