Load Imbalance

[delectric123]

I have a 150 amp 3 ph. breaker panel powered with 240/120 Delta. When doing a full load test i measured 105 amps on Phase A, 92 amps on Phase B, and 85 amps on Phase C. Unfortunately I forgot to measure the neautral current, though it shouldn't have amounted to much. It was less than 10 amps. Now how do i calculate the percantage imbalance?

 

[Smart $]

I have a 150 amp 3 ph. breaker panel powered with 240/120 Delta. When doing a full load test i measured 105 amps on Phase A, 92 amps on Phase B, and 85 amps on Phase C. Unfortunately I forgot to measure the neautral current, though it shouldn't have amounted to much. It was less than 10 amps. Now how do i calculate the percantage imbalance?

%imbalance = (max deviation - avg) ? avg ? 100%

 

[delectric123]

So i would have a 12% imbalance. Does that sound pretty reasonable?

 

[Smart $]

So i would have a 12% imbalance. Does that sound pretty reasonable?

Depends... If there are single phase loads, and the levels match their phase distribution, nothing I'd worry about. On the other hand, if the loading while taking the measurements should be balanced, that would demand further investigation, measurements, and analysis.

 

[delectric123]

mostly 3 ph. loads. but its the 240v 1 ph. loads that make the imbalance. i think its pretty reasonable.

 

[robbietan]

So i would have a 12% imbalance. Does that sound pretty reasonable?

utilities are regulated in terms of providing "quality' voltage to their customers. this includes a voltage unbalance of less than 2.5% at the point of common coupling PCC. current imbalance is never an issue unless it pertains to compressors/refrigerators. most of these equipment operate on stringent current imbalance and not on voltage unbalance as it should.