If you are indeed getting 20 amps on the neutral, they are not balanced if all loads are on and running. They may be balanced on paper, but if the calc's. on the drawings aren't exactly what the amprobe is, then you could and probably would see an inbalance. 20 amps on a 200 amp service is 10% and a little high I would think. Good luck.Hi,
I would like some suggestions. I am getting about 20A on my neutral of a 480-277V delta -wye transformer. All the loads are balanced. When I switch on one load at a time, the current on the neutral increases about 2 A. Any suggestions on possible problem?
Thanks
Shelly
I cant understand why there would be no current going back to ground through the EGC. Please help
Thanks for everyone's responses. The loads are balanced when all loads are on. The phase currents are approx 50A each, and the neutral current is 26A. What is very confusing to me is that there is only a current on the neutral X0 to ground within the transformer. There is no current flow on the transformer groundind conductor back to earth i.e. it appears to be a circulating current within the transformer. There is only lighting on these circuits so there should not be any harmonics. Additionally, we looked at a few other 3 phase 480-277V 3 transformers and found the same thing... with close to 50% of the phase current on the neutral. The transformer wiring seems to be ok. We did discover that the neutral was not bonded to the ground in the panel but this was corrected and the only difference was that the current was now split. I cant understand why there would be no current going back to ground through the EGC. Please help
Shells,
The readings you are getting sound very normal to me.
The Transformer with 50 Amp loads, has 26 Amps flowing on the Grounded Conductor, results in 52% Neutral load.
Normal is anything from 50%, through 70% - and at times, even 100%.
The only loads which will _COMPLETELY_ balance out (across a 4 wire network / multiwire circuit) will be Pure Resistance loads.
Looks like the 50 Amp circuits have an average power factor of 70%
Scott
Thanks Scott,
Can you provide some background? What is the basis for a normal neutral current between 50-70%? Are you saying that incandescent lighting circuits can be non-linear and is it because of a phase shift that the inbalance occurs also resulting in the neutral current? Does this also imply I have triplen harmonics? Also, if this is normal, then my transformer which is currently overheating is actually undersized? One transformer has already failed, this replacement is running hot. It seems the transformer is running at rated current, but if this is normal shouldnt the transformer have been rated to handle this neutral current and not overheat?