In a three-phase power system, how are the alternating currents arranged?

• A. In a parallel configuration
• B. All in phase
• C. Offset by 120 degrees
• D. In series

Answer: (C)

In a three-phase power system, the alternating currents are arranged so that they are offset by 120 degrees from one another. This arrangement is crucial for optimal power delivery and efficiency.

When the phase currents are spaced 120 degrees apart, they create a balanced three-phase system, which helps maintain a constant power flow. As each phase reaches its peak voltage at different times, this results in a more stable overall power level. The continuous rotation of the magnetic field generated by the alternating currents allows for smooth operation of motors and other electrical equipment, reducing vibrations and wear.

In contrast, arranging the currents in a parallel configuration or in series would not create the necessary three-phase sinusoidal waves required for this efficient power distribution. Being all in phase would lead to poor efficiency and power fluctuations, as the currents would peak and trough simultaneously, causing load imbalances. Thus, the 120-degree offset arrangement is fundamental to the functioning of three-phase power systems, ensuring balance and efficiency in energy transmission.