 The main generators weigh about 6 @,@ 000 tonnes each and are designed to produce more than 700 MW of power . The designed head of the generator is 80 @.@ 6 meters ( 264 ft ) . The flow rate varies between 600 – 950 cubic metres per second ( 21 @,@ 000 – 34 @,@ 000 cu ft / s ) depending on the head available . The greater the head , the less water needed to reach full power . Three Gorges uses Francis turbines . Turbine diameter is 9 @.@ 7 / 10 @.@ 4 m ( <unk> design / Alstom 's design ) and rotation speed is 75 revolutions per minute . Rated power is 778 MVA , with a maximum of 840 MVA and a power factor of 0 @.@ 9 . The generator produces electrical power at 20 kV . The outer diameter of the generator stator is 21 @.@ 4 / 20 @.@ 9 m . The inner diameter is 18 @.@ 5 / 18 @.@ 8 m . The stator , the biggest of its kind , is 3 @.@ 1 / 3 m in height . Bearing load is <unk> / 5500 tonnes . Average efficiency is over 94 % , and reaches 96 @.@ 5 % . 
