Capsule Hydroelectric Generator Unit

ahorizontal axial hydraulic generator unit with a rotary-blade hydroturbine, enclosed in a metal capsule housing. The first two capsule hydroelectric generator units, each with a rating of 195 kilowatts (kW), were made by the Swiss firm Escher Wyss in 1936 for the small RózdzieĔ Hydroelectric Power Plant in Poland.

The high efficiency of capsule hydroelectric generator units (greater capacity and smaller size in comparison with conventional vertical units; high power factors) results from the absence of any significant turns and twists of the flow and from the smoothness of the contours of the flow section of the generator unit. The capsule of such generator units may be on top, in the supply chamber, or on the bottom, in the suction pipe. The first type of arrangement is most commonly used. The generator of a capsule hydroelectric generator unit is sometimes connected to turbines through a step-up gear (usually a planetary booster) to increase its speed of rotation.

Capsule hydroelectric generator units are used in low-head hydroelectric power plants (with heads of 15–20 m), as reversible hydroelectric generator units at low-head pumped-storage hydroelectric power plants and at tidal electric power plants. In the USSR, for example, there are 20 17.5-MW capsule generator units in operation at the Kiev Hydroelectric Power-Plant. Capsule hydroelectric generator units are built with capacities up to 45 MW. Abroad, French firms have made the greatest progress in the development of capsule hydroelectric generator units.