Modern concepts use either doubly fed machines with partial-scale converters or squirrel-cage induction generators or synchronous generators ( both permanently and electrically excited ) with full scale converters.
22.
While synchronous generators capable of isolated plant operation are often used, small hydro plants connected to an electrical grid system can use economical induction generators to further reduce installation cost and simplify control and operation.
23.
Next to the inertia given by the parallel operation of synchronous generators, the frequency speed droop is the primary instantaneous parameter in control of an individual power plant's power output ( kW ).
24.
When multiple synchronous generators are connected in parallel to electrical grid, the frequency is fixed by the grid, since individual power output of each generator will be small compared to the load on a large grid.
25.
The four units installed in the plant have " Francis " vertical turbines with 125 MW power each; 3-Phase synchronous generators of 13.8kV voltage; and lifting transformers 13.8kV / 242 kV for the connection with the transmission substation.
26.
They are known as synchronous generators because f, the frequency of the induced voltage in the stator ( armature conductors ) conventionally measured in hertz, is directly proportional to RPM, the rotation rate of the rotor usually given in revolutions per minute ( or angular speed ).
