re: PMG
I understand. According to what I read, there are two PMGs per engine? Here is my source: "Each backup generator contains two permanent magnet generators (PMGs) that supply power to the flight control DC electrical system (refer to DC Electrical System)."
I can't find any specs on the web, so if you have any, that'd be great.
re: PSA batteries
Do you know what they are referring to? Are these the same as the main batteries? "Each PSA also uses a dedicated battery to prevent power interruptions to the related flight control DC bus. The batteries have limited capacity and are incorporated to supply power for brief periods during PSA power source transfers."