On Nov 1, 11:25*pm, DerbyBorn wrote:
I was being shown a new hydro plant at our local river a few days ago (From
the outside) The Project Manager was saying that the speed was finely
regulated by the water flow to give the right frequency. (That was as
technical as he could go on the topic).

This meant that in time of high flow it is throttled back considerably.
Isn't it possible to generate DC and convert it electronically to AC?
Wouldn't this mean that higher speed would give more amps?

In days of yore alternators linked to the mains had to be synchronised
and every alterntor runs/ran at exactly the same speed. Power output
is increased not by increasing the speed but by increasing the torque.
As long as the excitation is correct ,it is impossible for the
alternator to run at any other speed once locked in (ie on line)
If the excitation current is too low, the magnetic "bond" can break
and"pole skipping" occurs which can damage the machine.

However these days the output from small altenators is rectified to DC
and then connected to the mains with a special "grid tie inverter".
All these solar PV arrays and most wind turbines have grid tie
inverters.
http://en.wikipedia.org/wiki/Grid_tie_inverter

The advantage is that the plant can be run by non-technical staff and
reliability.
It can be safely left unattended too as everything is fail safe..

Huge grid tie inverters are now available.