NATE Air Conditioning and Heat Pumps Practice Exam

What voltage is measured between any two legs of the three hot legs in a delta-connected 240-V three-phase distribution panel?

1. 208 V

2. 240 V

3. 277 V

4. 380 V

The correct answer is: 240 V

In a delta-connected three-phase distribution panel, each leg (or phase) is typically 240 volts with respect to the neutral. However, when measuring the voltage between any two hot legs of the three-phase system, the voltage will be determined by the line-to-line voltage. In a delta configuration, the line-to-line voltage remains the same as the rated voltage for each line. Therefore, measuring between any two hot legs will yield a voltage of 240 volts, as each leg contributes its voltage directly to the overall system. This is a fundamental principle of how voltage operates in three-phase systems, especially in a delta configuration where all phases are directly connected. The other options refer to voltages that are either specific to different configurations (such as 208 V in wye configurations with 120 V lines) or typical for higher voltages in different systems, which do not apply in this case. Thus, the voltage measured between any two legs of the three hot legs in a delta-connected 240-volt three-phase system is indeed 240 volts.