Nominal vs Rated vs System Voltages

[pablo r. reyes]

I need the opinion of somebody about this.

What is the difference between the Nominal, Rated and System voltages? Your help will be appreciated.

 

[bphgravity]

Re: Nominal vs Rated vs System Voltages

System voltage is the actual measurable voltage present, nominal voltage is what you call it, and rated voltage is the voltge the equipment is designed to operate at. So for example, you have a 115V rated motor on a 120V nominal circuit that actually 127V RMS.

When in doubt always go to the definitions in Article 100 of the NEC.

 

[jdengr]

Re: Nominal vs Rated vs System Voltages

As I understand it, a motor may be connected to a 120v nominal circuit, but rated for 115v to account for possible voltage drop when in accual use. The circuit voltage has a tolerance of +/- 5%, typically, from the utility, so it's really somewhere between 114v to 126v, but we still call it 120v, nominal.

 

[charlie b]

Re: Nominal vs Rated vs System Voltages

The word "nominal" comes from a Latin word that is spelled the same, and that means "pertaining to a name." So a "Nominal 120 Volt System" is merely the name we give to voltages in that range. What the voltage is at any given moment has nothing to do with the name we give to the voltage range.

 

[bthielen]

Re: Nominal vs Rated vs System Voltages

I agree with Charlie and Brian. We refer to a 120v system but we all, or most of us, realize that we are referring to most any system from 110vac to 130vac. It's a name and nothing more.

Bob

 

[pablo r. reyes]

Re: Nominal vs Rated vs System Voltages

Thanks to everybody for your clear replies. This site really helps.