Journeyman Electrician Exam (NEC)General Electrical Knowledge and Plan ReadingEasy
A client has a 480V, 3-phase, 3-wire delta system. What is the phase-to-neutral voltage available from this system?
- A240V
- B0V
- C277V
- D480V
Show answer & explanationAnswer & explanation
Correct answer: B. 0V
A 3-wire delta system does not inherently provide a neutral conductor, meaning there is no phase-to-neutral voltage available for loads requiring a neutral reference. While a corner-grounded delta or high-leg delta might provide a grounded conductor or a neutral point respectively, a standard 3-wire delta does not.
Why the other options are wrong
- A. This might be seen as a phase-to-ground voltage in some specific delta configurations (e.g., high-leg delta), but not a general phase-to-neutral.
- C. This is the phase-to-neutral voltage for a 480Y/277V wye system, not a delta.
- D. This is the phase-to-phase voltage of the delta system.
Delta System Phase-to-Neutral Voltage
In a standard 3-wire delta electrical system, there is no inherent neutral conductor, and therefore no phase-to-neutral voltage available.
- Phase-to-phase voltage is present.
- No neutral point is typically derived without additional equipment (e.g., grounding transformer).
- Used primarily for 3-phase motor loads.
Memory trick: Delta has no 'N'eutral, Wye has 'Y'our neutral.