What is the difference between a standard AC system and an "AC wild" system? How does the latter work?
Frequency wild Unregulated AC is generated using alternators.
The alternator runs at various RPM (which varies the frequency) since it is driven by the engine.
The difference is that regulated AC is of fixed frequency. Better for motors, pumps, etc.
Unregulated AC was used for things like windshield wipers and windshield heating. DC inverters were used when regulated AC was needed.
Edit: On a plane like the ATR 72, it is indeed referred to as AC Wild.
It is used for heating the windshield, propellers, and probes. Among other systems that don't require regulated AC.