A linear dc motor, like a rotating dc motor, generates mechanical force by the interaction of current in conductors and magnetic flux provided by permanent rare-earth magnets. It is constructed of a stator assembly and a slider. The stator assembly serves as the body and contains a laminated steel structure with conductors wound in transverse slots. The slider contains one or more sets of magnets, commutation components, a bearing surface, and its body completes the magnetic flux path between the magnets.
The brush-type slider carriers two sets of brushes. One set picks up the power from a pair of copper rails, and the second set transfers power into the conductors located under the slider through commutator segments. Two of three phases are energized at any one time.
The brushless slider contains an additional set of magnets which activate Hall-effect sensors and solid-state switches to commutate the motor windings. A dc linear motor positioning system is extremely stiff, fast, and efficient. It is capable of precision accuracy to 0.1 micron and does not deteriorate with wear. It can drive loads directly, obviating the need for gears and lead screws. Its typical range of thrust and travel is 2.5 to 2,500 lb and a few inches to about 4 ft.
