Two three phase transformers with ratings shown below are paralleled on their secondary side.
Transformer No. 1 – 1000kVA, 4160V/480V, Z = 5.0%
Transformer No. 2 – 1500kVA, 4160V/480V, Z = 8.0%
The maximum load in kVA the transformers can supply (combined) without overloading any one , is determined by the transformers impedance. They load up inversely proportional to their impedance.
Before calculating the load, we need to get the transformers on the same base impedance. This can be done using the following formula.
Changing transformer T1 base impedance to T2 base impedance
= j0.075 pu
When transformer T1 is completely loaded to 1000kVA
T2 can be loaded to
The total load the transformers can supply combined is
1000kVA + 937.5kVA = 1937.5kVA