Determine the approximate short circuit current available

[rasilva]

Using the given information, determine the approximate short circuit current available at the transformer secondary: 13,800-277Y/480V, 2500 kVA, 5% Impedance

60,000 A
54,500 A
42,000 A
37,500 A
25,000 A


first should be 480Y/277 not 277y/480.

basically this would be the calculation. I= (2500*1000)/(480*1.732)= 3007.08
z= (100/5)= 20
short circuit = 3007.08*20= 60189

so i would just go with the closest answer correct? and also they should fix the error on 277Y.

[Flashman]

I work it out to the same answer. Seems you did it right and I would go for the closest answer.




Using the given information, determine the approximate short circuit current available at the transformer secondary: 13,800-277Y/480V, 2500 kVA, 5% Impedance

60,000 A
54,500 A
42,000 A
37,500 A
25,000 A


first should be 480Y/277 not 277y/480.

basically this would be the calculation. I= (2500*1000)/(480*1.732)= 3007.08
z= (100/5)= 20
short circuit = 3007.08*20= 60189

so i would just go with the closest answer correct? and also they should fix the error on 277Y.

[madMAX]

The questions clearly states "determine the approximate short circuit current". Go with the closest answer.

[rasilva]

The questions clearly states "determine the approximate short circuit current". Go with the closest answer.


yes sir but its wrong wording that what confused 277y/480 doesn't exist, 480y/277 exist

[Shaun103]

Using the given information, determine the approximate short circuit current available at the transformer secondary: 13,800-277Y/480V, 2500 kVA, 5% Impedance

60,000 A
54,500 A
42,000 A
37,500 A
25,000 A


first should be 480Y/277 not 277y/480.

basically this would be the calculation. I= (2500*1000)/(480*1.732)= 3007.08
z= (100/5)= 20
short circuit = 3007.08*20= 60189

so i would just go with the closest answer correct? and also they should fix the error on 277Y.

2500 x 100
1.732 x .480 x5

250,000/4.1568= 60,142

[Ronwilson1801]

Could someone explain the math a little more in depth? Never mind I was confused in Z, but looking over it again I understand.

[carl21]

480 *1.732= 831.36

why do you multiply 480 by 1.732?

[Kalbi_Rob]

480 *1.732= 831.36

why do you multiply 480 by 1.732?

Original equation is for single phase transformer:
IFLA=(KVA*1000)/EL-L

To calculate for 3 phase voltage, the square root of 3 (1.732) must be multiplied by the voltage:
IFLA=(KVA*1000)/(EL-L*1.732)

EL-L for both of theses transformers is 480V, one is single phase and the other is 3 phase.