The limit load control has the task of making it possible to fully exploit the power from a drive motor, even if additional loads are activated and the sum of the power demanded by all loads would exceed the drive power installed.
A limit load control is often installed on mobile machinery to prevent an overload and therefore stalling of the combustion engine (Figure G 24). Here, as a rule, power is supplied as a matter of priority to the hydraulics for operating the machinery, i.e. the movement velocity of the machine (corresponds to the flow rate to the variable pump) is reduced automatically to the advantage of the other drives if the combustion engine would otherwise be overloaded. For this purpose, e.g. a limit load high response proportional valve measures via a measuring orifice a rotation speed drop (engine loading), which results in a reduction in the variable pressure at the pump adjustment and therefore causes the pump to pivot back.
Figure G 24: Propulsion drive with limit load control