A windmill produces AC voltage, with increasing voltage as the turbine spins faster. If you know the max safe RPM, you could find the associated max safe voltage (V_safe). Additionally, when the leads of a turbine are shorted with each other, it induces a braking effect.

If you place a Zener diode with a V_safe breakdown voltage (maybe slightly lower for a safety margin), wouldn’t the AC voltage above V_safe go towards braking the turbine?
I’m interested because of two reasons:
 1. Preventing the turbine from spinning itself apart
 2. The V_safe I’m interested in would actually be the max value of a switch mode buck converter


[![Really badly drawn turbine with two leads and two zener diodes][1]][1]


  [1]: https://i.sstatic.net/rX5AL.png