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220v socket/plug

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  • 220v socket/plug

    I am going to wire up my new milling machine. The motor is 3 phase - I will be driving that from a single phase VFD. The power feed is 110v. I also need to power some relay circuitry in the mill from 110v. I want to make up a single 4 wire power cord that will have neutral, ground and both hot leads. Distribution will be handled in a box at the mill. My question is what is the best type of plug/socket for this application. The power requirement is fairly small, as the motor is 1hp and the rest does not add up to much.

  • #2
    Hubbell twist-lock type.. You can get them at HD even.


    • #3
      There is a standardized NEMA designation for plugs/recep in each class of service and nominal current rating. Each class and rating is designed to prevent accidental interchange with other classes and current ratings.

      The common 115 volt 15 Amp duplex wall outlet has a NEMA designator of "5-15". Your local electrical supply house will have a counter chart listing the full NEMA plug/recep range both locking and non-locking. If electrical work is in your future ask the nice counterman for a Leviton "Industrial Specification Guide for Plugs and Connectors". Hubbel and others have equivalent publications. They 'splain it all with pictures.

      A home user having only one or two machines should comply with the NEMA plugs receptacles classes of service. Home shops never get smaller. It's a VERY good idea to standardize on plug/outlets in your growing workshop using the plugs and receptacles approved for your service regardless of what you may have found at a garage sale. I know a guy who has to physically change plugs on his bandsaw if he moves it across his shop.

      You're looking for 230 single phase w/neutral and ground. Officially this is called "125/250V 3 pole 4 wire gounding". The NEMA designation is "14". If you want a 20 Amp nominal rating specify "14-20" if 30 Amp, 14-30.

      If you want a locking plug the designation for your specific service will be L14-20 or L14-30.

      If you want to use your VFD on other machines by swapping plugs on the three phase end you should select a plug/recept for 230 volt three phase grounding service such as NEMA 15-20.

      There's a further refinement when a termional "P" or "R" is added to designate plug or receptacle - or "C" for connector (cord mounted receptacle as on an extension cord) and so-on.

      I use locking plugs on my 230 single and three phase service. L6-30 for single phase and L15-30 respectiveely.

      [This message has been edited by Forrest Addy (edited 08-22-2003).]


      • #4
        Thanks Oso and Forrest. I am afraid I already have a problem with 220 sockets, because I have 5 3hp machines that run 220 single phase. They are presently on the 20 amp three wire socket/plug system. On the plus side I wired my three 220 circuits with four outlets/circuit since I don't run more than two machines at once. I will have to run a neutral to one box and change one socket to twist lock for the mill.


        • #5
          If you intend to use coolant on a machine the connections should be liquid tight.
          I just need one more tool,just one!


          • #6
            A cheaper alternative is "Electric Dryer cords & outlets". Hubbel also makes the same plugs and outlets to higher quality standards for extreme duty in industrial applications. The Hubbel twist locks are ideal in areas where there is a chance of the cord being yanked out by accident. If you use a Hubbel outlet there is little chance of any plug "falling out" on its own - they grip the plugs pretty tight! Hospital Grade is the highest quality in the Hubbel line.