This example shows a transmission built of a variable-displacement pump, and a fixed-displacement hydraulic motor. Pipelines between the source and motor are connected by two replenishing valves (check valves) and a charge pump on the pump side and two pressure-relief valves on the motor side. The motor drives a mechanical load consisting of inertia, viscous friction, and time-varying torque. The system is tested with varying pump flow rate and motor torque load.
The plots below show the flow rate through the hydrostatic transmission and the pressure drop across the motor. As the motor reaches its nominal pressure, flow is diverted through a pressure relief valve.