What is the current flowing in the feeder conductor if all loads are operating in a 3-pole breaker scenario with a 30 kVA load?

Study for the Independent Electrical Contractors (IEC) Year 2 Part 3 Test. Use flashcards and multiple choice questions with hints and explanations to prepare confidently. Get exam-ready now!

To determine the current flowing in the feeder conductor for a 30 kVA load in a three-phase system, one can use the formula for calculating the current in a three-phase circuit:

[ I = \frac{P}{\sqrt{3} \times V \times \text{Power Factor}} ]

In this scenario, since the power factor is not specified, we often assume a power factor of 1 for simplicity in calculations unless otherwise noted.

Given:

  • ( P = 30 , kVA = 30,000 , VA )

  • For a typical line-to-line voltage of 480 V in industrial settings.

Substituting into the formula, we have:

[ I = \frac{30,000}{\sqrt{3} \times 480} ]

Calculating ( \sqrt{3} ) gives approximately 1.732, thus:

[ I \approx \frac{30,000}{1.732 \times 480} \approx \frac{30,000}{829.44} \approx 36.2 , A ]

This value indicates the current per phase for a balanced load. However, since you specified that all loads are operating, the calculation must

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