Thismaster thesis addresses a pumpwhich PMC Servi has suggested for application in hydraulic transmission in a wind turbine. A mechanical and hydraulic model is constructed and several standard valves are tested and the NG63 valve is chosen for further analysis. By conducting CFD-analysis a new deflector valve is designed. By inserting this into the non-linear model, an efficiency of the system is found to be 0.983127 which was 0.74 percentage points higher than the NG63 valve. Multiple valves are then tested, and the set-up with two valves as both in- and outlet is chosen with a resulting efficiency of 0.992038. Themodel is then expanded with a friction and leakage model for the piston rings applied on each piston of the pump. This model is then attempted utilised on the slipper pad bearing between the eccentric shaft and the piston rod. Due to a lack of non-linear behaviour of the pressure in the slit the model proved incapable of modelling the fluid film height and thus a steady state model is constructed instead. With friction and leakage from the piston ring and slipper pad included, the overall efficiency is found to be 0.98937.