Question

A 277/480-volt, 3-phase, 4-wire feeder supplies a continuous lighting load of 120,000 VA. What minimum standard size overcurrent protective device is required? (No harmonic currents are considered.)

Answer 1

To determine the minimum standard size overcurrent protective device required for a 277/480-volt, 3-phase, 4-wire feeder supplying a continuous lighting load of 120,000 VA, we can use the formula: Minimum Overcurrent Protective Device Size = Load Voltage / (1.732 * Load Current). Substituting the given values, we can calculate the load current and determine the minimum overcurrent protective device size.

Step-by-step explanation:

To determine the minimum standard size overcurrent protective device required for a 277/480-volt, 3-phase, 4-wire feeder supplying a continuous lighting load of 120,000 VA, we can use the formula:

Minimum Overcurrent Protective Device Size = Load Voltage / (1.732 * Load Current)

Given that the load voltage is 277 volts and the load power is 120,000 VA, we need to calculate the load current:

Load Current = Load Power / Load Voltage

Substituting the values into the formula, we get:

Load Current = 120,000 VA / 277 volts

After calculating the load current, we can determine the minimum overcurrent protective device size:

Minimum Overcurrent Protective Device Size = 277 volts / (1.732 * Load Current)

By calculating this expression, we can find the minimum standard size overcurrent protective device required.