# Transformer Sizing for 120/208-Volt Panel

## What is the smallest calculated size 480 - 208/120 3Ø, 4-W wye transformer needed for a panel with specific loads?

The panel has 80 amps of 120-volt loads connected to AØ 1-pole breakers, 80 amps of 120-volt loads connected to BØ 1-pole breakers, and 80 amps of 120-volt loads connected to CØ 1-pole breakers. It also has three sets of 3-pole breakers supplying three-phase loads of 20, 60, and 80 amps.

## Smallest Calculated Transformer Size:

The smallest calculated size for the 480 - 208/120 3Ø, 4-W wye transformer needed for the panel is 75.76 kVA.

To determine the required transformer size for the panel, we need to calculate the total load in kVA. Starting with the single-phase loads connected to the AØ, BØ, and CØ 1-pole breakers, each at 80 amps and 120 volts, we find that it sums up to 9.6 kVA per phase.

Adding up the single-phase loads for the three phases, we get a total of 28.8 kVA. Moving on to the three-phase loads, the formula to calculate power in kVA for three-phase systems is Power = sqrt(3) * Voltage * Current. Plugging in the values, we calculate the total three-phase loads to be 46.96 kVA.

Summing up the single-phase and three-phase loads, we arrive at a total load of 75.76 kVA. Therefore, the smallest calculated size for the 480 - 208/120 3Ø, 4-W wye transformer required to supply this panel is 75.76 kVA.

It's essential to accurately size the transformer to ensure it can effectively handle the connected loads and meet the power requirements of the panel.