The motor has the speed regulated by controlling a switch (4) in series with the main winding (1) so that the current is only allows to flow through the latter for a portion of each cycle. The switch closures engender HF noise signals which are suppressed so that they do not cause mains interference by splitting the main winding (1) into two identical halves (2,3) with the switch (4) inserted bween them, so that each half (2,3) acts as a suppression coil for the HF noise signals. Pref. an auxiliary winding (9) in series with a capacitor (10) is connected in parallel with the main winding (1), which pref also has a parallel anti-interference capacitor (11). The switch (4) may comprise a triac its control circuit comprising a diac (12), a capacitor (14) and a regulating potentiometer (16).
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