Circuit Calculations

[Gaggsy]

I have a 40A circuit breaker on a switch board which supplies a 220V distribution board, the 3 phases of the 40A breaker pull 6.3A, 4.6A and 7.2A. Can I just add these together to find the total current being pulled by the DB?

 

[varri79]

Hi Gaggsy,
You shouldn't add all three currents for total current as these currents are individual pahses.

we can give only total power pulled by DB by adding individual powers.

if at all, you want to give total current of DB, you may take the max current i.e.7.2A in your case.

 

[mpparent]

Deja Vu?


Mike

 

[Cooda76]

Hey Gassy
This is a 3phase system, all the currents are in a 120 degree relationship, you just cannot add them algebrically, now when the load is unbalanced, the term" how much current is not relevant but as varri79 said max. current is 7.2 A that will work" the other thing you can do it to find powers and define the rating of DB like
(220/1.73*6.3)+(220/1.73*4.6)+(220/1.73*7.2)
Hope works !