Busbar
Beginner
A thick metal bar running up the back of a rack that carries electricity to every server.
Novice
A solid copper bar that distributes DC power along the rack. Servers clip onto it instead of using individual power cords.
Expert
In Open Rack, a rear 48 V-class DC bar fed by rack-level power shelves. Distributing at ~50 V instead of 12 V cuts current fourfold and resistive loss sixteenfold for the same conductor.
Explained in Board and server (Systems).