If the RH load bus DC power fails, what happens to the No.2 Inverter relay?

• A. It remains energized and continues to be powered from the RH load bus.
• B. It is automatically deenergized and is then powered from the emergency bus.
• C. It bypasses to the start bus.
• D. It powers the emergency bus directly.

Answer: (B)

When a DC power path is designed with an inverter relay tied to the RH load bus, the relay coil is energized from that main bus to connect the No.2 inverter to it. If the RH load bus DC power fails, the coil loses power and the relay releases, disconnecting the inverter from the failed bus. The system is arranged so the inverter then sources its supply from the emergency bus, keeping essential AC power available. So, the No.2 inverter relay automatically deenergizes and the inverter is powered from the emergency bus.