Help Translating Motor ID Plate and Suggestions on Twist-Lock Plug
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  1. #1
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    Default Help Translating Motor ID Plate and Suggestions on Twist-Lock Plug

    So I have been searching like crazy, but just wanted to verify that I am on the right track here and look for suggestions. Working towards getting my Sidney Model 32 16" lathe up and running. It has a 10 hp motor as seen here:

    sidney-motor-plate-01.jpg

    I purchased an American Rotary AD 20 hp rotary phase converter for it. Due to the local electricians being swamped in this area, it is going to be some time before anyone can get out here. I have done a fair amount of basic residential wiring for home projects, but nothing along these lines. I am just trying to get my head around everything that I need and have everything ready.

    Where I am at this point, per the literature from American Rotary I will need to run the RPC off of a 60 amp single phase breaker. I will have 2 awg wire running from the single phase panel to the RPC panel. 6 awg will run from the RPC panel to both the idler and the lathe. Due to planning to move in the next year or so, I would prefer not to run conduit around the shop. The lathe will be located with 20 feet of the single phase panel, so I was hoping to only hard wire the RPC in (will be removed when we move, but will need to pass inspection prior to moving) and use a plug in for the lathe's connection to the RPC panel.

    My question is: looking at the plate I see that the FLA is right at 30 amps. Would a 30 amp 3 phase twist lock plug work in this scenario or does it need to be up-sized due to the extra current draw at startup? If it does need to be up-sized, does someone have a recommendation on a good 50 amp plug. I am finding lots of 30 amp options, but the 50 amp options seem to be limited.

    Thank you for your help!

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    A 60 amp single phase beaker may not cut it, anyway 40amp 3 phase beaker, 50 amp plug, size 6 wire. Motor will have a surge (LRA) of 180 amps 3 phase...Phil

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    HUBBLE makes 50 amp QD plugs - don't know if suitable for 3 phase

    HUBBELL WIRING DEVICE-KELLEMS 50 Amp Industrial Grade Locking Connector, 50A, Non-NEMA NEMA Configuration, Black'/'White - 3D322'|'CS6364C - Grainger

    you naturally need its receptacle

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    Why are you contemplating the twist lock cord end? Even if you move in the not to distant future, hard wiring a suitable cord through suitable strain relief right at the junction box of the motor is not unheard of..and much more cost effective than a plug and connector.

    On a side note, a 16" lathe with a 10hp motor is pretty husky. My 17" lathe come from the factory with a 7 1/2 hp motor and even at that, I downsized it to a 5 hp and have never run out of oink!

    Stuart

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    Thank you everyone for your responses!

    Phil - The single phase 60 amp breaker is per American Rotary's installation manual. Obviously this could be up-sized, I was just going off of their instructions. I did up-size the rest of the wiring as their manual calls for 3 awg between the single phase panel and the RPC panel, I bought 2. And it called for 8 awg going to the idler and load, I have 6.

    John - Thank you, I will check into that.

    Stuart - MN changed it's code a few years ago. Any new permanent wiring run in a shop must be run entirely in conduit whether it is in a wall or mounted on the outside of the wall. One of my buddies was putting up a 40' x 50' detached garage with the wiring in the walls right as this went into effect and the electrician had to come back and redo the entire installation after the inspector cited him for it. I am trying to not put up conduit and instead run the cord over when I need to use it. American Rotary has provisions to mount a 3 phase breaker and a receptacle directly in the RPC panel. This would mean that the only conduit needed would be between the single phase panel and the RPC panel which will be right next to it.

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    You could presumably use greenfield (flexible conduit) as the machine connection, if they will not accept cords. I see your point, however, a receptacle is the end of "permanent" wiring, and the rest of the wiring after the receptacle is outside of the range of the NEC. (It "belongs" to UL)

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    I reached out to American Rotary to pose this question to them. Per their engineering department I "can get away with our 30 amp receptacle along with a 35 Amp three phase breaker as well for your set up". I had sent them the same picture of the motor plate as was posted here. So apparently I was over thinking this and their engineering department does not foresee an issue with the temporary spike due to motor start up. Thank you everyone for your input!

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    NEC article 430.109(F) requires the plug/receptacle be rated for the motor HP, this can get quite expensive because common devices have a fairly low HP rating. NEC Table 210.21(B)(3) limits a 30A receptacle to 30A overcurrent protection, the only way to use a 35A breaker,is by hard wiring.

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    The other way around this is to use a different type receptacle which does carry the current/voltage ratings needed.

    The receptacle need not be normally used for the application, so long as the ratings are OK, AND there is NO use of that receptacle at a different voltage within the "facility". So you are not limited to only "the usual" receptacle and plug caps, which can in fact get fairly expensive.

    It is "unconventional", but the NEC allows the usage. The key is that there must be no other usage in the "facility" (which may be interpreted by a strict inspector as "the building", for rented space), so that confusion is not a factor. It is helpful to label the receptacle with the voltage it carries, and that may be required.

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    Quote Originally Posted by johnoder View Post
    HUBBLE makes 50 amp QD plugs - don't know if suitable for 3 phase

    HUBBELL WIRING DEVICE-KELLEMS 50 Amp Industrial Grade Locking Connector, 50A, Non-NEMA NEMA Configuration, Black'/'White - 3D322'|'CS6364C - Grainger

    you naturally need its receptacle
    Yes it is, we've used these extensively at work here for some time.

    The three lugs are hot, the ground is along side, and also the tip on the plug.


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