What are the 3 phase voltages in the USA


We have to install UV dryers in the U.S.A.

In Europe, 3 phase + ground (Y) is common in industrial sites. Phase to phase around 400 VAC, ground to phase 230 VAC.

What is common in the U.S.A. One hears, 480 VAC delta, no ground?

Is there a standard?


For systems 600V and less:

Most common in the USA is 480Y/277 , 3phase, 4 wire grounded system for equipment in commercial and industrial sytems. Commercial lighting normally is 277V.

Convenience outlets, whether residential, commercial or industrial are always 120V, a part of 208Y/120V, Y system. Therefore, a system of step-down transformers , 480V delta to 208Y/120V is always present in commercial and industrial systems.

As with any other place, exceptions are always present which include ungroundned or groudned delta systems. Always check with your clients.

And for your further informatin:

Resiential systems are normally fed by 2 phases and a neutral (single phase, 3 wire) which in fact is part of a 208Y/120V , Y grounded system. 480/277 is never used in the residential systems.

Many older residential systems would have 240/120V, single phase 3 wire systems.

Hope this helps you cause.

Above is a snippet.

What rbulsara mentioned above is 100% correct, however I would like to add that high-resistance grounded neutrals are becoming more common even in the US (at least as far as our industrial clients are concerned.) Commercial clients not so much.

1 Like

Actually that system is used only in large apartment buildings.
Single family dwellings and small apartment buildings use 120/240 Volt single phase.
Some areas in Canada started to phase out 277/480 Volt wye systems in favour of 347/600 Volt wye systems.
Even though I started to see the first 347/600 Volt systems mandated by supply utilities almost 50 years ago, there are still a lot of 277/480 Volt systems around.
There are a few 480 Volt delta systems around. Some of them are four wire delta with 240/480 Volts available on one phase with the center tap being grounded.
Some are corner grounded.
Some use zig-zag or wye-delta transformer banks to ground through an impedance.
Listing the common voltages:
120/208 Volts
277/480 Volts
You may occasionally find a 347/600 volt system that came in from Canada.
Less common are 240 Volt and 480 Volt delta systems.
The common line to line voltages are multiples of 120 Volts.
If you are new to North American systems be aware that the standard motor voltages are multiples of 115 Volts.
Thus motor voltages are:
115 Volts
230 Volts
460 Volts and
550 Volts.
Dual voltage motors are series parallel rather than star delta.
Hence, 230/460 is a common motor voltage.
You will often find motors rated for 208, 230/460 Volts.
They are becoming more common.

There are very few 347/600 Volt generators available.
I worked a turn around at a major tar sand plant some years ago.
The plant was 347/600 Volts.
We brought in 480 Volt rental generators.
The rental firm also provided open delta auto-transformers to boost the voltage up to 600 Volts.
Then a lot of air extraction fans were rented. They were only available at 460/480 Volts.
Wye connected auto-transformers were located in the areas where the fans were needed and dropped the voltage back down to 480 Volts.

1 Like