New York State Master Electrician Practice Exam

In a three-phase, 4-wire delta-connected system, which phase should the high leg be connected to?

1. A phase

2. B phase

3. C phase

4. Grounded neutral

The correct answer is: B phase

In a three-phase, 4-wire delta-connected system, the high leg, also known as the "wild leg," is typically connected to the B phase. This is because, in a delta connection, the phases are arranged such that one of the phases, which is often associated with the higher voltage potential relative to the neutral, serves as the high leg. In a typical delta system with a grounded neutral, the B phase is identified as the phase that carries a higher line-to-neutral voltage when compared to the others. This is important for ensuring proper operation of equipment and maintaining safety standards. By connecting the high leg to the B phase, it avoids an imbalance in the system and ensures that the other phases, A and C, are properly utilized with a lower voltage potential. This configuration also helps to prevent situations where sensitive equipment might be subjected to higher than expected voltages. The other options would not align with standard practices in electrical systems. For instance, connecting the high leg to A or C phases could lead to operational inefficiencies and potential damage to equipment, since it would disrupt the expected voltage relationships within the system. Connecting it to the grounded neutral is also impractical, as the neutral does not carry any phase voltage while serving as a point