🔍 Key Concepts
• Wye-connected (Y) secondary with neutral N2 and how line-to-line vs line-to-neutral voltages relate (480 V line-to-line, 277 V line-to-neutral).
• How each transformer (T1, T2, T3) in the bank is connected between a specific primary phase (A1, B1, C1) and a specific secondary line conductor (A2, B2, C2) plus the neutral N2, per illustration 3.
• What happens to measured voltages if the secondary winding of one transformer is open versus if it has shorted turns (effect on that phase-to-neutral and adjacent line-to-line voltages).
💭 Think About
• Looking at figure 3, trace which transformer provides the connection between B2 and the neutral N2, and which one between C2 and N2. How would an open in that winding affect B2–N2 or C2–N2 readings?
• If one secondary is open, which line-to-line voltages should disappear, and which should remain? Compare that expectation to the given A2–B2, B2–C2, and C2–A2 values.
• Would a few shorted turns typically give you zero volts, or just a reduced but non‑zero voltage on that phase? Use that to eliminate one of the options involving shorted turns.
✅ Before You Answer
• Verify which physical transformer (T1, T2, or T3) is in series with the A2–B2, B2–C2, and C2–A2 paths in the illustration.
• Confirm that a 277 V reading means that phase’s winding is still connected from that line to the neutral N2 and is energized normally.
• Check which answer choice matches the pattern: one phase has normal line-to-neutral voltage but no contribution to certain line-to-line voltages, indicating an open in a specific transformer’s secondary.