Electrician's Licensing Practice Exam

In a three-phase delta system, how is the leg with the highest voltage identified?

1. As the "A" leg

2. As the "C" leg

3. As the "B" leg

4. As the "D" leg

The correct answer is: As the "B" leg

In a three-phase delta system, identifying the leg with the highest voltage involves understanding the configuration of the phases and how they relate to each other, particularly in terms of phase angles and voltage levels. The delta configuration consists of three phases, typically labeled A, B, and C, where each leg is positioned 120 degrees apart in relation to the others. In a balanced three-phase system, the voltages on each leg are equal in magnitude but differ in phase. To determine the leg with the highest voltage, it's important to recognize that, while phase labels vary based on specific applications or systems, one phase is conventionally designated as having the highest voltage due to either maximum load or an imbalance that might occur under certain conditions. In many systems, the B leg is often identified as the one with the highest voltage due to the typical configuration and loading patterns in industrial applications, which can result in B being the most heavily loaded phase or influenced by external connections. This does not rule out the presence of variations in specific installations, but for the sake of a general understanding in training scenarios or multiple-choice examinations, B is commonly assigned the highest voltage designation. Thus, in this context, recognizing B as the leg with the highest voltage is an important concept grounded in