a unit consisting of a coaxial hydraulic turbine and a counterrotor generator. It was first proposed by the Soviet scientists M. A. Kasparov and V. V. Semenov in 1950.
In a counterrotor unit the armature rotor of the generator is mounted on the hollow rotor shaft of the coaxial turbine, and the stator (counterrotor) is connected to the counterrotor shaft, which is inside the rotor shaft. The generator's rotor and counterrotor turn in opposite directions. Such units are characterized by good operation of the suction pipe (in which, under all conditions, the flow does not swirl), which somewhat reduces the drop in efficiency caused by fluctuations in pressure head, and also by a high speed of rotation of the rotor relative to the counterrotor, which makes possible a reduction in the number of generator poles and thus in its size.