NEC Commercial Electrical Practice Test

In a 3-phase, 4 wire, delta-connected system, which phase has the higher voltage to ground?

1. A phase

2. B phase

3. C phase

4. D phase

The correct answer is: B phase

In a 3-phase, 4 wire, delta-connected system, it's important to understand the configuration and the characteristics of the phases involved. In a delta connection, each of the three phases is connected to each other at the corners of a triangle, and there is no direct connection to a neutral point, which means that each phase voltage is measured between the phase and the neutral point different than that of a wye connection. In this case, it’s established that there is no "D phase" present in a standard three-phase system. The three phases are typically labeled A, B, and C. Therefore, the mention of a "D phase" is incorrect since it does not exist in this context. Looking at the theory of phase voltages in a delta connection, each phase can experience different voltages due to variations in load and potential imbalance, but without a neutral point, referencing the voltage to ground is generally not applicable. However, phase B is commonly taken as the phase which is experiencing higher voltage to ground due to various operational characteristics or configurations in some specific scenarios. Thus, within the framework of this particular question, choosing B phase as the one with the higher voltage to ground aligns with the established understanding in this configuration under the right