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?

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?

• A. 125 A
• B. 150 A
• C. 175 A
• D. 200 A

Answer: (B)

To determine the minimum standard size overcurrent protective device for a 120/208-volt, 3-phase feeder supplying a continuous load of 37.5 kVA, it is essential to first calculate the continuous load in amperes and then apply the appropriate standards for overcurrent protection. The formula to convert kilovolt-amperes (kVA) to amperes (A) for a three-phase load is: \[ I = \frac{P}{\sqrt{3} \times V} \] Where: - \( I \) is the current in amperes - \( P \) is the load in watts (or kVA converted to watts) - \( V \) is the voltage (line-to-line for three-phase, which in this case is 208 volts) The continuous load is 37.5 kVA, which can be expressed in watts as: \[ 37.5 \, \text{kVA} \times 1000 = 37500 \, \text{VA} \] Now we can substitute the values into the formula: \[ I = \frac{37500 \, \text{VA}}{\sqrt{3} \times 208 \,

To determine the minimum standard size overcurrent protective device for a 120/208-volt, 3-phase feeder supplying a continuous load of 37.5 kVA, it is essential to first calculate the continuous load in amperes and then apply the appropriate standards for overcurrent protection.

The formula to convert kilovolt-amperes (kVA) to amperes (A) for a three-phase load is:

[

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

]

Where:

• ( I ) is the current in amperes

• ( P ) is the load in watts (or kVA converted to watts)

• ( V ) is the voltage (line-to-line for three-phase, which in this case is 208 volts)

The continuous load is 37.5 kVA, which can be expressed in watts as:

[

37.5 , \text{kVA} \times 1000 = 37500 , \text{VA}

]

Now we can substitute the values into the formula:

[

I = \frac{37500 , \text{VA}}{\sqrt{3} \times 208 ,