Which items provide DC power to the SME DC busses?

• A. TR 5 and 6
• B. TR 1 and 2
• C. TR 3 and 4
• D. TR 7 and 8

Answer: (A)

The main idea is identifying which transformer-rectifier units actually feed the SME DC busses. Transformer-rectifier units convert AC power into the DC that powers the busses, and the diagram shows which TRs are connected to each DC bus. In this system, the SME DC busses are connected to the outputs of TR 5 and TR 6, making them the DC power sources for those busses. This pairing provides redundancy and ensures a stable DC supply to the SME busses. The other transformer-rectifier units (TR 1 and 2, TR 3 and 4, TR 7 and 8) are wired to different busses or parts of the system and do not energize the SME DC busses, so they are not the correct sources for those busses.