Electric vacuum pumps from HELLA are used to support or solely generate the vacuum for the pneumatic brake boosting system. Under certain driving conditions or depending on the engine design, insufficient or no vacuum can be provided to the brake booster via the intake manifold of an internal combustion engine. The UP 28 variant can support the system by generating an additional vacuum (support application) The UP 5.0 and UP 30 can provide the pneumatic vacuum supply alone ("stand alone" application). In this case, the pump acts as the sole source of vacuum and ensures sufficient supply for the brake booster and any auxiliary consumers. Structure and function: The operation of the vacuum pumps is based on the rotary vane compression principle. The pump contains a rotor that is eccentric to the pump chamber. The slides embedded in the rotor slide along the inner wall of the pump chamber. Rotation continuously compresses the volume enclosed by the slides. This change in cell volume causes a vacuum with the effect that air is drawn in from the brake booster via the pneumatic line system of the brake system by the vacuum pump.