the stator as denoted by an arrow i fig3 a and b are cross sections of two different surfaces parallel to the longitudinal direction of the stator a stator 21 is shown to have many magnetic teeth 22 formed with a constant pitch in the longitudinal direction of the stator a mover 23 which is composed of a permanent magnet 24 which is long in the longitudinal direction of the stator has its magnetizing axis perpendicular to that direction two cores 29a and 29b sandwich the permanent magnet 24 three separate three phase coils 30a 30b and 30c are wound over the two cores 29a and 29b three groups of magnetic teeth 25a 25b and 25c are formed on the stator side surface of the core 29a and three groups of magnetic teeth 26a 26b and 26c are formed on the stator side surface of the core 29b a narrow gap must be maintained between the stator 21 and the mover 23 for that purpose the guiding means 31a and 31b are provided which maintain the air gap and guide the mover 23 toward the longitudinal direction denoted by an arrow i of the stator 21 the guiding means 31a and 31b may be rollers but for the simplification of the figures they have been omitted from the drawings except for fig2 b in this example many magnetic teeth 22 which are formed on the stator 21 are arranged in the longitudinal direction of the stator with a constant pitch but the magnetic.