Abstract: The invention describes a vortex finder for a cyclonic separator. The vortex finder includes a plurality of stationary vanes around which incoming air is guided into the vortex finder, in which a side of the vanes facing the incoming air is provided with a protrusion at a stagnation point. The protrusion is shaped so as to guide the incoming air into the vortex finder, and have a concave side following a shape of a neighboring vane, and a rounded top. Further, the protrusion has a height in a range between 70% and 130%, and in a range between 85% and 115% of a gap width between the vanes. The gap width between adjacent vanes increases from an outside to an inside of the vortex finder. A vacuum cleaner that includes a cyclonic separator has such a vortex finder.

Abstract: A vortex finder, for a cyclonic separator, includes a plurality of stationary vanes having a round convex front end around which incoming air is guided into the vortex finder, wherein, where air separates from the plurality of stationary vanes inside of the vortex finder, a cross-section of the plurality of stationary vanes has only one sharp edge. Preferably, a mean line of the cross-section of the plurality of stationary vanes does not cross a chord line in an upstream half of the cross-section. Preferably, a side of the plurality of stationary vanes facing the incoming air is provided with a protrusion at a stagnation point. The protrusion may be shaped so as to guide the incoming air into the vortex finder, and may have a concave side following a shape of a neighboring vane, and a rounded top.

Abstract: In a vacuum cleaner (VC) comprising a motor-fan aggregate (A), and a control for controlling a power setting (PS) of the motor-fan aggregate (A), a processor (?P) is arranged for protecting the motor-fan aggregate (A) from overheating and/or entering a stall regime in dependence on a comparison of a parameter relating to a flow rate with a threshold that is representative of the rotation speed (N) of the aggregate (A). The threshold may depend on a power setting (PS) of the motor-fan aggregate (A) or a current through the motor-fan aggregate (A). The parameter relating to the flow rate may be a pressure difference between on the one hand a position upstream or downstream of the motor-fan aggregate (A), and on the other hand, ambient, a pressure difference over a known component, a pressure difference over the motor-fan aggregate (A), and/or—if the threshold depends on the power setting (PS)—a rotation speed of the motor-fan aggregate (A).