Measure of speed control,in which the variable pumps are used, which only deliver as much hydraulic fluid as required in the circuit. This keeps the power loss smaller than the control with throttle. However, it also depends on the type of adjustment: Whereas in the case of pressure reduction, the flow rate is placed under the full pressure, the pressure at the pressure/current controller (p/Q controller) is only slightly greater than the load pressure (Figure P 36). If large flows need to be controlled, a multi-pump system may be more cost-effective, consisting of one variable pump and several constant pumps, which can then be connected as desired (Figure P 37).
As larger masses are to be moved in the pump with the pump control than in the case of the control with throttle, the dynamic behaviour attainable is lower: Frequencies of between 5 and 30 Hz are expected, depending on the construction type and size.
Alternative: Control with throttle.
Figure P 36: Pump control with pressure control (a) and pressure/current control (b)
Figure P 37: Multiple constant pumps combined with a single variable pump