kalanjeya said:So simple !
The formula is here ,
single phase current = Tranformer capacity in VA / 1.732*208
Hang onto this link:steveng said:thanks a lot, the formulas some times trip me up!
rattus said:I find it confusing to compute the "sum" of the line currents which strictly speaking add to zero.
kalanjeya said:Rattus , this is not mathematical current , the SUM you said is vector current.
When you have 30 KVA three phase transformer, it is capable of load to 3 numbers of 30 KVA single phase load .
That is not correct. It should be 30,000/ (208 * 1.73) and then the answer is 83.37 amps. You are doing (30,000/208) * 1.73.30000 / 208 * 1.732 = 249amps
don_resqcapt19 said:Steve,
That is not correct. It should be 30,000/ (208 * 1.73) and then the answer is 83.37 amps. You are doing (30,000/208) * 1.73.
Don
celtic said:VA/(1.732*208) would be more accurate, no?
Not that there is anything wrong with that method, I prefer to calculate available line current on a 208Y/120 system as:don_resqcapt19 said:Steve,
That is not correct. It should be 30,000/ (208 * 1.73) and then the answer is 83.37 amps. You are doing (30,000/208) * 1.73.
Don
Smart $ said:Not that there is anything wrong with that method, I prefer to calculate available line current ...
Smart $ said:Not that there is anything wrong with that method, I prefer to calculate available line current on a 208Y/120 system as:
30,000VA ? (120V ? 3) = 83.33...A (i.e. 83 1/3 Amperes)This stems only from the fact that the 208 voltage is rounded, whereas the 120 voltage is not...
120V ? √3 = 207.846V
However, on a 480Y/277 system, the 277 voltage is the one that is rounded...
(480V ? √3 = 277.128V)...so I calculate available line current as, for example:
30,000VA ? (480V ? √3) = 36.084A
The one constant through all my calculations, if I'm doing it on a scientific calculator, is that I always use √3 opposed to 1.73 or 1.732. The number of keys pressed is usually the same or less.
rattus said:Smart, it is pointless to compute these results beyond 3 significant figures.
hardworkingstiff said:Rattus, there you go getting practical,