For the A320 family, is the "off-side engine generator" the same as the "emergency generator driven by the RAT"? I can't find the location of the "off-side engine generator" on the A320.
Offside simply means opposite, and it's to do with the AC bus supply priority.
For the A320 the priority is:
- Onside, e.g., left engine IDG for AC BUS 1
- External power
- Offside, e.g., right engine IDG for AC BUS 1, meaning the left engine's IDG has failed or taken offline.
Neither the off-side and on-side engine generators are RAT generators. They are both just the generators attached to each engine. As far as I can tell, if there is a failure of one of the parallel electrical buses the off side is the failed side and the on side is the operating side.