Feeder Protection Size Calculation for Motors

What size feeder protection is required for the motors?

1. 10 HP, 230 volts three-phase motor

2. 15 HP, 230 volts three-phase motor

Answer:

The required feeder protection size for the motors needs to be determined based on their Full Load Current (FLC).

To calculate the FLC for each motor, we can use the formula:

Fault Current (in amps) = (HP × 746) / (volts × √3 × efficiency)

For the 10 HP motor:

(FLC) = (10 × 746) / (230 × √3 × 0.85)

(FLC) ≈ 23.8 amps

For the 15 HP motor:

(FLC) = (15 × 746) / (230 × √3 × 0.85)

(FLC) ≈ 35.7 amps

Based on these calculations, the required feeder protection size can be determined accordingly for both motors.