Abstract: A vacuum cleaner having a suction nozzle and a dust bag (12) which is connected to the nozzle, for instance, by a tube connection, and a turbo-fan unit (27) driven by an electric motor and placed after the dust bag seen in the flow direction. The impeller (29) of the turbo-fan unit is driven at a speed above 50,000 rpm. A primary air stream created by the turbo-fan unit (27) leaves the unit via an outlet (30) to atmosphere. The vacuum cleaner also creates a secondary air stream which at least partially cools the electric motor (32) and which flows into the electric motor via one or several cooling air inlets (44) which are separated from the primary air stream. The secondary air stream can be created by a cooling fan which is separate or integral with the impeller, by a venturi-type nozzle, or by suction created by the impeller.

Abstract: A device for controlling a three-phase induction motor that is driven by an inverter connection. The inverter is furnished to be fed with full-wave rectified grid alternating voltage (U) and supply the motor's various phases (R, S, T) with the drive voltages phase-displaced in the normal way and which consist of mainly square, in relation to a virtual zero reference level, positive and negative half-periods which alternate at a fixed or adjustable drive frequency corresponding to the required speed. The full-wave rectified grid alternating voltage (U) supplied to the inverter is arranged to be supplied to respective motor phase (R, S, T) via an electronic switch connection (TR.sub.1H, TR.sub.1L ; TR.sub.2H, TR.sub.2L ; TR.sub.3H, TR.sub.3L) whose respective on and off periods are determined by the drive frequency which is generated by an oscillator device (15; 25). The last mentioned is arranged to be supplied with a voltage (U.sub.

Abstract: A vacuum cleaner includes a suction fan driven by an electric motor, a suction nozzle connected to the intake side of the fan via a dust container, and a cord to supply electric power to the motor. The motor is electronically controlled and adapted to be driven at a speed such that the suction fan operates at a speed of at least 50,000 rpm. The suction fan comprises a fan Impeller of the turbo fan type.

Abstract: A switched mode power supply includes a pair of capacitors serially connected across a supply input and a pair of switching transistors serially connected across the supply input. The output load circuit is connected between the junction of the capacitors and the junction of the transistors by way of a series conductor. A capacitor is connected in parallel with the load and a further capacitor, which may consitute stray capacitance, is also connected between the junctions of the transistors and the junctions of the capacitors.