The Pelton wheel was invented by the American engineer Lester Alan Pelton around 1882.
In the impulse type of hydraulic turbine, the runner (Pelton wheel) converts the kinetic energy in one or more jets of high-velocity water into torque in the turbine shaft. The runner consists of a definite number of buckets, each of double-bowl construction, located on the rim of a central disc.
The forwarded velocity of the portion of the jet which enters each bucket is reduced nearly to zero in the bucket. The kinetic energy in that portion is thereby converted into a force acting on the moving bucket, and producing a torque on the turbine shaft. The force of the jet is applied only during the time that the water is in the bucket. The impulse of a force is defined as the product of the force and the time during which it acts.
Pelton turbines are made with either vertical or horizontal shaft. The vertical-shaft turbine usually has only one runner and up to six jets. Most horizontal-shaft units have one or two jets per runner and one or two runners per turbine. Horizontal turbines usually cover those combinations of power and head for which vertical turbines either are not as economical or are too small to permit accessibility for maintenance.