Whenever I ponder about something I use Google. As suspected Googling "AVR generator" confirms it means Automatic Voltage Regulator.
Now, who would've thunk that a voltage regulator could be anything but automatic..?
It wouldn't be a regulator then, would it, according to "our electronic dictionary", or..?
Further refining the Google search brings up
this thread that disassembles an AVR, and also provides a link to a manufacturers service manual - with diagrams.
If this is something the OP can use I don't know - since he hasn't been overly informative.