Minimum Feeder Calculation for Four Motors

What would be the minimum feeder to supply the following set of four motors?

Three, 3.0 HP, single-phase, 115 volt motor. One, 7.5 HP, three-phase, 208 volt motor.

Which option would be the closest to the correct answer?

1. 66.7 amps
2. 132.25 amps
3. 112.65 amps
4. 42.5 amps

Answer:

It's determined that the minimum feeder required to operate the set of four motors would be 114.33 amps.

Calculating the minimum feeder required to supply multiple motors can be an exciting challenge for engineers and electricians. In this scenario, we have a combination of three single-phase motors and one three-phase motor that need to be supplied with power.

To find the minimum feeder, we first need to determine the current each motor draws. For the three 3.0 HP single-phase 115 volt motors, the current can be calculated using the formula P = IV. This results in 26.09 Amps for each motor, totaling 78.27 Amps for all three motors combined.

For the 7.5 HP three-phase 208 volt motor, the current calculation yields 36.06 Amps. Adding this to the total current needed for the single-phase motors gives us a minimum feeder requirement of 114.33 Amps.

Among the provided options, the closest one to our calculated value is 112.65 amps, which would be the correct choice for the minimum feeder to supply the set of four motors.