# How do you calculate 3 phase current of a transformer

FAQ | Feb 14,2023

1. The theoretical formula of three-phase transformer I and secondary current in power system is as follows: primary current = transformer apparent power (S) divided by square root of 3 divided by 0.9 divided by primary side voltage. Secondary current = transformer apparent power (S) divided by square root of 3 divided by 0.9 divided by secondary side voltage. 2, 10KV to 400V, 6KV to 400V three-phase distribution transformer primary current empirical formula is as follows: 10KV, the primary current is equal to the transformer apparent power (S) remaining to 0.066KV, the primary current is equal to the transformer apparent power (S) remaining to 0.13, the actual secondary current of the transformer is related to its secondary load, the calculation result of the secondary current mentioned in the above (1) is the value when the secondary load reaches the rated value, please note. Example: Calculation of primary and secondary current of 10KV/0.4KV, 630KVA three-phase transformer: 1. Theoretical principle I1=630KVA÷1.732÷0.9÷10KV≈40AI2=630KVA÷1.732÷0.9÷0.4KV≈1010A2; empirical formula I1=630KVA×0.06≈38A

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