What defines a "three-phase" power system?

A "three-phase" power system is defined by its use of three alternating currents that are offset by 120 degrees from each other. This phase displacement allows for a more balanced and efficient power distribution compared to single-phase systems. Each phase can carry a varying load, which can help to stabilize the overall power system and reduce the risk of outages or fluctuations in power supply.

In a three-phase configuration, the use of multiple phases means that the delivered power is consistent and smooth. It helps in minimizing the amount of conductor material required while still providing a powerful and reliable energy supply, making it essential for industrial applications and large electrical systems.

The other choices reference concepts that don't accurately describe a three-phase power system. For instance, direct currents do not involve phase offset like alternating currents do, and single-phase systems operate differently than three-phase systems. Additionally, the mention of only two phases does not fit the definition of a three-phase system, as it specifically requires three distinct phases for its operation and benefits.