Abstract: In accordance with the invention, the motor includes: a rotor component composed of a shaft (1) of magnetic material provided with regularly spaced projections (3), and a stator component comprising at least three multipolar stators encircling the shaft consecutively, each polar core having cavities on the shaft side so as to constitute projections (13) of the same width and spacing as those of the shaft, with the spacing between stators being such that the projections of the shaft and those of the polar cores face one another for only one of the stators. A tight casing (2) is arranged to intersect the stator magnetic circuit and magnetic parts (21) extend the polar core to the interior of the casing. Application to nuclear reactors.