how does it it work

Hi Malae, in response to your question, i can describe how my wind turbine works to charge a battery.  The wind generator has a group of windings on a rotor(moving part), and a group of permanent magnets on a stator(stationary part).  The blades  turn the rotor in this magnetic field and generate a three phase AC voltage that is sent down a three conductor wire to a charge controller.  The charge controller rectifies the AC voltage to a DC voltage, which is then used to charge a bank of batteries.  A microprocessor in the controller monitors the output voltage and shuts down the turbine at a preset full charge voltage for the batteries. I think that a hydro generator works much the same, just uses water instead of wind to turn the rotor, but i have no specific knowledge of the hydro variety of generator.