The motor has a passive conductive track, comprising an inductor winding intended to be traversed by a direct current, of superconducting material, placed in a cryostat, rotary with the cryostat around an axis parallel to theplane of the track and perpendicular to the direction of relative movement of the track and of the inductor. An auxiliary polyphase winding parallel to the track and wound so as to create a sliding field, synchronous with the field of the inductor, is arranged mechanically so that relative motion between it and the axis of the inductor in translation along the track is absent. The auxiliary polyphase winding may be flat and comprise coils whose separation increases from its medium plane, in line with the axis of the inductor.