Question

A machine shop is fed by a 300kVA, 480V 3-phase transformer to a load that consists ofmany small motors. The total shop load is 225kVA and the power factor is 0.74 lagging.

What is the maximum line current in the feed lines from the transformer to the facility as it is currently configured?

Answer 1

The maximum line current from the transformer to the machine shop with a load of 225kVA at 0.74 power factor is 201 A.

Step-by-step explanation:

The student's question is about the maximum line current that can flow from a 300kVA, 480V 3-phase transformer to a machine shop with a load of 225kVA at a power factor of 0.74 lagging. To find the maximum line current, we can use the power factor to calculate the real power and then the formula for power in a three-phase system:

Real Power (P) = Apparent Power (S) × Power Factor (pf)

In this case, Real Power (P) = 225kVA × 0.74 = 166.5 kW.
Since P = √3 × V × I, we can rearrange the formula to solve for I (Line Current):

I = P / (√3 × V)
I = 166.5 kW / (√3 × 480V) = 201 A.

Therefore, the maximum line current for the feed lines from the transformer to the facility is 201 A.