E. Short Circuit Current Calculation Examples (ignoring motor contribution) 3 – Phase Transformer Example kVA = 1500 Secondary Voltage = 480V LL Impedance = 4.5% 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 = 1500 𝑘𝑘𝑘𝑘 𝑘𝑘 𝑥𝑥 1,000 √ 3 𝑥𝑥 480 𝑉𝑉 𝐿𝐿𝐿𝐿 ≅ 1,806 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑆𝑆ℎ𝑜𝑜𝑜𝑜𝑜𝑜 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝐶𝐶𝐶𝐶𝐶𝐶 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 = 1,806 𝐴𝐴 𝑥𝑥 4.5% 100 𝑍𝑍 ≅ 4,190 𝐴𝐴 Single-Phase Transformer Example Transformer kVA = 37.5 kVA Voltage = 240V LL Percent Impedance = 1.8% 𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 = 37.5 𝑘𝑘𝑘𝑘 𝑘𝑘 𝑥𝑥 240 1,000 𝑉𝑉 𝐿𝐿𝐿𝐿 ≅ 156 𝐴𝐴 𝑆𝑆ℎ𝑜𝑜𝑜𝑜𝑜𝑜 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝐶𝐶𝐶𝐶𝐶𝐶 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 = 156 𝐴𝐴 𝑥𝑥 1.8% 100 ≅ 8,667 𝐴𝐴
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