Which factor directly affects the required conductor size?

The required conductor size is primarily affected by current. This is because the amount of current flowing through a conductor determines how much heat will be generated due to electrical resistance. As current increases, the heat produced in the conductor can rise to levels that may damage the conductor or pose safety hazards. Conductors must be sized appropriately to carry the expected load current without exceeding the temperature ratings, ensuring efficiency and preventing overheating.

When selecting conductor sizes, it involves considering not only the current but also various derating factors such as ambient temperature and insulation type. However, the initial and most significant factor driving the sizing process is the current. Proper sizing ensures that conductors can handle the maximum expected load and prevents issues like voltage drop or conductor burnout. This understanding is crucial in the field to maintain system reliability and safety.