For a Pelton wheel turbine theoretical maximum efficiency and the speed factor for maximum efficiency can be obtained from
1
\(\frac{1}{2}(\frac{1+cos \beta _2}{2})\); \(\frac{U}{V_1}\)
2
\(\frac{1}{2}(1- cos \beta _2)\); \(\frac{U}{V_{r1}}\)
3
\(\frac{1}{2}(1+ cos \beta _2)\); \(\frac{U}{V_{1}}\)
4
\(\frac{1}{2}(1+ cos \beta _2)\); \(\frac{U}{V_{r1}}\)