Abstract: The motor has a first element carrying toothed studs and windings mounted on the studs and a second element constituted by a mass of magnetic material on which second element there are formed teeth capable of effecting a relative movement with respect to the teeth of the first element, the number of teeth of the first element being different from the number of teeth of the second element so that said teeth are capable of modifying the reluctance of the magnetic circuits that they constitute respectively with said studs, in order to produce a relative movement of the two elements when the windings are supplied with a poly-phase current. The number of teeth of the two elements satisfies the following relation:.vertline.Z.sub.I - Z.sub.II .vertline. = skin which:Z.sub.I = number of teeth of the first element including fictive teeth which may be assumed to be located between the studs;Z.sub.