Fluid-operated dynamoelectric converters for medical or dental devices are described. The dynamoelectric converters have: a fluid line which is designed in one piece with an outer sleeve of the dynamoelectric converter and protrudes at its end which faces away from the dynamoelectric converter beyond a connecting end of the medical or dental device; a fluid-operated impeller which is designed in one piece with a rotor sleeve receiving the magnetic element; a one-piece, sleeve-shaped magnetic return element which surrounds the rotor and the electric winding of the stator and has a magnetically conductive material.