Which device allows AC ESS BUS to power ESS TRU 2 after certain failures?

• A. ESS TRU 2 Transfer Contractor
• B. ESS XFER Switch
• C. DC Service Switch
• D. ADG Power

Answer: (A)

The device that allows the AC ESS BUS to power ESS TRU 2 after certain failures is the ESS TRU 2 Transfer Contractor. This component acts as the bridge that connects ESS TRU 2 to the AC ESS BUS when a fault or loss of normal power path occurs, ensuring ESS TRU 2 can continue supplying the essential DC bus. In other words, it reconfigures the power path so TRU 2 can still deliver power to critical systems even if other sources are unavailable. The ESS XFER Switch is typically a manual control for transferring power paths, not the automatic bridge used in these failure conditions. The DC Service Switch handles DC servicing functions and isn’t the mechanism for re-sourcing TRU 2 from the AC ESS BUS. ADG Power provides an alternate emergency source if needed, but it does not perform the transfer to ESS TRU 2 from the AC ESS BUS.