The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Parking lot pole light swap....
by ghost307
Today at 06:25 AM
International Wire Colour Codes
by Tjia1981
Yesterday at 12:08 PM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 7
ghost307 7
renosteinke 6
Potseal 4
Who's Online
0 registered (), 288 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#130152 - 02/18/06 01:32 PM 3 phase wye neutral current
randyagr Offline
Junior Member

Registered: 03/07/04
Posts: 6
Loc: Lanark, IL US
Been trying to understand 3 phase wye neutral currents by reading this.
Does this mean neutral current is the same for one 120v load and 2 120v loads, but drops to zero for 3 120v loads assuming all loads equal? Have only worked on 3 phase center tapped Delta in this area, so I know the neutrals cancel each other since both 120v legs are from the same phase, but I'm not sure I get this 3 Phase wye. Thanks, Randy

#130153 - 02/18/06 05:29 PM Re: 3 phase wye neutral current
Larry Fine Offline

Registered: 02/18/05
Posts: 684
Loc: Richmond, VA
Randy, look at it mathematically: Start with an equal load, say 20 amps, on all three phases. The neutral current is the sum of the three currents, including the phase angles, which equals 0.

Now, remove the load on one phase, as well as its contribution to the neutral sum, -20 amps from each. This results in 20 amps subtracted from the previously-balanced zero neutral current, meaning 20 amps.

So that leaves 20 amps on two phases, and 20 amps on the neutral. Now, let's "check our math" by reversing the process: Each amp drawn by the third phase reduces the neutral current by the same amount, until it's back to zero.
Larry Fine
Fine Electric Co.


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals