Reply by CaptainKlutz

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Posted on 3-Phase Electrical Service

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1784 posts in 1978 days

#1 posted 04-21-2018 12:45 AM

You can run directly between with converter and tool, assuming they have sufficient space for the wiring connections in existing junction boxes, and proper strain relief for wire/conduit.

The details vary depending on interconnect method:

-Temporary power connection between independent source and tool can be accomplished with most an suitable 50A plug/receptacle and portable cable rated wire, as long as wire junctions are inside a rated box. Since you have control of a remote 3 phase source, and tool connection: You can get away with using most any 250VAC 50A plug that has 4+ poles to support tool, such as regular NEMA 14-50P, providing you label it 3 phase. There are very few NEMA rated 50A plugs, so many options used in industrial applications are custom and costly. I suggest using a locking version like this one to help avoid any confusion between household oven circuit and your 3 phase system?

- Permanent power installation requires that any wiring junctions be inside a rated junction box. So need a box at/on converter which holds conduit feeding machine and a box at/on machine when power terminates into machine. You may or may not be able to use existing junction boxes, it depends on style and size. If tool is not bolted to floor, the conduit from a fixed junction box to machine must be flexible version.
As Loren stated, it is common for industrial sites to use a breaker or disconnect junction box near machine for lock out during maintenance. This industrial protection lock out disconnect is added even if machine has junction box mounted directly on it due differences in “line of site” requirements for power disconnects, as most machine junction boxes are too low for line of sight across a room.

If you want to connect more than one tool at time to 3 phase power for a permanent installation, then you will need to install a separate 3 phase panel board with breakers to protect individual 3 phase circuits. If is not allowed to have more than 1 device on a 3 phase circuit. Remember breakers protect wire in circuit, not tool.

IMHO – If you do not need portable power via temporary connection, it is usually cheaper to run wire run inside conduit between junction boxes.
Cost for 50A plug/receptacle, plus 6AWG flexible cord is significant (50A locking plugs cost $125+ pair, while junction box cost $20 each?). Another benefit of using conduit is allows use of higher 75 degree temperature rating for THWN/THHN wire, which means only need 8 AWG for 50A permanent install instead of 6AWG for temporary wire. Four conductors of THHN cost about $1.50 foot, while 6AWG SOOW/SEOOW portable wire costs $2.50+/foot.

Hope this helps.
Enjoy your new tool.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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