What is the minimum standard size overcurrent protective device required for a 120/208-volt, 3-phase feeder supplying a continuous load of 37.5 kVA?

To determine the minimum standard size overcurrent protective device for a 120/208-volt, 3-phase feeder supplying a continuous load, it is important to apply the relevant load calculations and derating factors.

First, you need to convert the load from kVA to amperes. For a 3-phase system, the formula to convert kVA to amperes is:

[ I = \frac{P}{\sqrt{3} \times V} ]

Where:

• ( I ) is the current in amperes.

• ( P ) is the power in kVA.

• ( V ) is the voltage in volts.

In this case, the load is 37.5 kVA and the voltage is 208 volts.

Calculating the amps:

[ I = \frac{37.5 , \text{kVA}}{\sqrt{3} \times 208 , \text{V}} ]

Calculating (\sqrt{3} \approx 1.732):

[ I = \frac{37.5 , \text{kVA} \times 1000 , \text{(to convert to VA)}}{1.732 \times 208} ]