Abstract: The invention concerns the stator of an electric motor comprising a packet a stacked laminations provided with laterally open slots for receiving the active portions of the windings for the motor poles in which the surface of each slot carries an inner layer of a molded insulating material applied to the insulation surface of the slot, the layer in each slot being united with the layer of each one of the adjoining slots at the two outer sides of the stator by means of an insulating lateral layer so that the combiantion of the layers forms a one-piece molded layer over the slot region, thus providing good insulation of the magnetic circuit in electric motors designed to have a long service life at elevated temperatures such as those used for central heating circulation pumps.