Nozzle converts hydraulic head H into a free jet at v_i = √(2gH); split buckets deflect flow ~165–180° at optimal rim speed u = v_i / 2
operating regime
High hydraulic head (15 to 1,800+ meters) with low-to-moderate volumetric flow rate (low specific speed)
efficiency or isp
Peak hydraulic efficiency η = 4u(v_i − u)/v_i² → up to 92% in utility installations (100% theoretical at u = v_i/2)
originator
Lester Allan Pelton (tested 1878 in Nevada City, California; US Patent 233,692 in 1880)
Core Principles & Analysis
Invented during the California Gold Rush by carpenter Lester Allan Pelton and patented in October 1880, the Pelton wheel replaced inefficient flat-paddle water wheels with twin spoon-shaped buckets divided by a central splitter ridge.
When the bucket rim rotates at exactly half the velocity of the incoming water jet (u = v_jet / 2), the water jet makes a U-turn inside the curved bucket and drops out in the stationary reference frame with nearly zero residual velocity, transferring almost 100% of its momentum to the runner.
Operating at atmospheric pressure in a single impulse stage, Pelton turbines dominate high-head Alpine hydroelectricity — notably the three 423 MW Pelton units at Switzerland's Bieudron Power Station fed by a record 1,883-meter vertical water head from the Grande Dixence Dam.