What is the smallest calculated size transformer that can supply a panel with 80 amps per phase load and multiple 3-phase loads?

To determine the smallest calculated size of the transformer that can adequately supply a panel with an 80 amps per phase load, and additional multiple 3-phase loads, we first need to calculate the appropriate KVA rating needed for this transformer.

Start by finding the total amperage required across the three phases. For a 3-phase load, the formula to calculate KVA is:

[ KVA = \frac{\sqrt{3} \times Volts \times Amps}{1000} ]

Assuming a standard voltage of 480 volts for commercial applications, the step would involve plugging this value along with the current per phase (80 amps) into the formula:

1. Calculate KVA for one phase:

[ KVA = \frac{\sqrt{3} \times 480 \times 80}{1000} ]

2. Simplifying this:

[ KVA = \frac{1.732 \times 480 \times 80}{1000} ]

[ KVA ≈ \frac{66503.2}{1000} ]

[ KVA ≈ 66.5 ]

Now, this calculation indicates the transformer needs to support at least 66.