# NEMA Twist Lock plugs for motors



## 3DDesign (Oct 25, 2014)

I always matched the overcorrect protection of the motor.


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## don_resqcapt19 (Jul 18, 2010)

RubyTuesday said:


> How do you size a twist lock plug for a motor? Say the motor draws 30 amps, could I use a plug that is rated for 30 amps? Or would the plug have to be rated for something higher like 125%? Section 430.109 (F) in the NEC says, "...plug and receptacle having ratings no less than the motor ratings shall be permitted to serve as the disconnecting means." I think this answers my question, but I just wanted to make sure I wasn't overlooking anything else. Thanks


You have to look at the horsepower rating of the plug and receptacle.


> 430.109(F). Cord-and-Plug-Connected Motors. For a cord-and-plug connected motor, *a horsepower-rated attachment plug and receptacle,* flanged surface inlet and cord connector, or attachment plug and cord connector having ratings no less than the motor ratings shall be permitted to serve as the disconnecting means. ...


The horsepower ratings of 30 plugs and receptacles range from 2 to 10 depending on the system voltage and number of phases.
What is the rating of the motor in question?


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## oliquir (Jan 13, 2011)

i always put at least 30-50% bigger plug so it can last, a plug used near 100% of its capacity will overheat if motor runs all day long


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## RubyTuesday (Oct 19, 2014)

don_resqcapt19 said:


> You have to look at the horsepower rating of the plug and receptacle.
> The horsepower ratings of 30 plugs and receptacles range from 2 to 10 depending on the system voltage and number of phases.
> What is the rating of the motor in question?


Well the question I had was for future reference because someone usually will order what I need, but I wanted to know how to do it for myself and correctly, So the "motor" I mentioned was hypothetical. But now I'm looking at the nameplate for a motor that I have worked with and its 49.6A @ 230 V and the HP is 20. I would have to find a plug and receptacle rated for 20 HP and 50 A?


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## telsa (May 22, 2015)

http://www.meltric.com/html/specification-guide.html

If you're talking motors in THAT power range -- you're talking pin and sleeve.

AFAIK, every NEMA player has a toe in that market.

Meltric is a one-trick pony, near as I can tell, dedicated towards rapid motor swap out in a production setting.

Twist-lock connectors are -- to my mind -- only appropriate for modest loads... and I have a fist full in my 'private collection.'

In a Locked Rotor Crisis, I'd hate to attempt touching a twist-lock cord cap!


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## don_resqcapt19 (Jul 18, 2010)

We just did a replacement of all of the pin and sleeve welding receptacles in a plant with the Meltric ones. They had a safety finding from their corporate safety department saying that you have to have the power off before plugging or unplugging the 480 volt 60 amp pin and sleeve devices. The choice was to install disconnects next to the existing pin and sleeve receptacle or to install a new receptacle with a built in disconnect. They chose the Meltric device.

Where the Meltric device is used as a motor disconnect, they are available with first break control contacts that can be used to turn a VFD off before the power leads are disconnected where the device is used on a motor fed from a VFD. Of course for this to work the control contacts have to put the VFD in a "coast to stop" mode.


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## retiredsparktech (Mar 8, 2011)

I, myself was rather inpressed with Meltric devices. They seemed well engineered..


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