Question 2.9: Currents in a Single-Phase, Three-Wire System. A three-wire,......

Renewable and Efficient Electric Power Systems [1073600]

Currents in a Single-Phase, Three-Wire System. A three-wire, 120/240-V system supplies a residential load of 1200 W at 120 V on phase A, 2400 W at 120 V on phase B, and 4800 W at 240 V. The power factor for each load is 1.0. Find the currents in each of the three legs.

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The 1200-W load at 120 V draws 10 A; the 2400-W load draws 20 A; and the 4800-W, 240-V load draws 20 A. A simple application of Kirchhoff’s current law results in the following diagram. Notice that the sum of the currents at each node equals zero; also note that the currents are rms values that we can add directly since they each have current and voltage in phase.

Example 2.9

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