NEMA Plug hp Rating - what does 'hp" value really indicate?

[WSpier]

So in looking up the NEMA plug configuration for a 30A 220V service, all three plugs listed are rated at 2.0 hp. What does that number really indicate? I ask because I know motors in the 4-5 hp range call for 30A 220V service, but there appears to be no 30A 220V plug rated over 2.0 hp. So does the hp value indicate something else, like a running load and not a spike load (starting amp draw, or heavy motor resistance load)? Or is there a special plug that actually has a higher NEMA hp rating? If the latter, where are those listed?

 

[Jraef]

So in looking up the NEMA plug configuration for a 30A 220V service, all three plugs listed are rated at 2.0 hp. What does that number really indicate? I ask because I know motors in the 4-5 hp range call for 30A 220V service, but there appears to be no 30A 220V plug rated over 2.0 hp. So does the hp value indicate something else, like a running load and not a spike load (starting amp draw, or heavy motor resistance load)? Or is there a special plug that actually has a higher NEMA hp rating? If the latter, where are those listed?

To attain a HP rating on a device, it must be tested to SAFELY INTERRUPT the flow of current if used in such a way. So in the case of a plug and receptacle, that means that someone will pull the plug from the receptacle while the motor is running. A running motor, as a spinning inductor if you will, serves to help sustain an arc as the conductors are separated. The typical NEMA wall plug and receptacle combos that you can order are not designed for that, or at least for HP ratings above what you have found so far. There are plug and receptacle combinations that have higher HP ratings, they're just not going to look like the NEMA blade or twist lock style, they will be pin and sleeve and there will be a long tube surrounding the pins so that when you pull it out under load, the arc is safely contained or shunted to ground. In the older configurations, there were called "Arc Tight" for this reason, and commonly called "welder receptacles" because welders too are late inductors. Then the Europeans introduced us to all plastic versions, and more recently there are some that now have a spring loaded disconnect contact in the receptacle that has a the official rating of being a local motor disconnect (Meltric).