Step 1: Determine the Circuit Ampacity

To find the size of the conductor, we need to determine the circuit ampacity, which is the maximum current that the conductor can safely carry. In single-phase systems, the ampacity is directly proportional to the load current.Given load current: 380 ampsStep 2: Calculate Voltage Drop

The voltage drop in the feeder conductors will reduce the voltage at the load. We need to calculate the voltage drop to ensure that the voltage at the load is within acceptable limits.Assume a maximum allowable voltage drop of 5%.Maximum allowable voltage drop = 5% of 120 volts = 6 voltsStep 3: Determine Conductor Resistance

Using Ohm's law, we can calculate the resistance of the feeder conductors:Resistance = Voltage drop / CurrentResistance = 6 volts / 380 amps = 0.0158 ohmsStep 4: Calculate Conductor Length

The total conductor length is twice the distance from the source to the load:Total conductor length = 2 x 300 feet = 600 feetStep 5: Calculate Conductor Size

Using the NEC (National Electrical Code) and the assumptions above, we can select the appropriate conductor size based on the circuit ampacity, voltage drop, and conductor length.According to the NEC, the minimum conductor size for this application is 350 kcmil copper or 500 kcmil aluminum.

Note: These calculations assume a single-phase circuit. The voltage drop calculation is an approximation. Actual voltage drop may vary depending on conductor material and type.* It is advisable to consult a qualified electrician to confirm the conductor size and ensure compliance with NEC requirements. Flag for review