GB1337887A - Direct current traction motor - Google Patents

Abstract

1337887 Dynamo-electric machines NOVIPB SA 15 Feb 1972 [5 March 1971] 6898/72 Heading H2A In a D.C. motor comprising a rotatable, slotted, laminated armature 18 and a multipolar field assembly of which each pole comprises two axially spaced elements, one a permanent magnet 26 and the other a field coil 29 disposed on an iron core 28, the axial space d between the coils and magnets is at least twice as great as the air gap between the armature and field assembly. In the four-pole D.C. traction motor shown, the magnets are of ferrite and are fixed to the stator frame. In a modification (not shown), the magnets are angularly movable. The field coil may comprise simply a series winding or both a series and a separate winding. To minimize leakage through the armature between the two elements of each field pole, either the armature core includes a number of insulating foils in the area of the gap between the pole elements or the leakage flux return path (frame 16 in the motor shown) includes an annulus of non-magnetic material (35, Fig. 3a or 36, Fig. 2a). The motor may have a conical air gap (Figs. 3, 3a) or an axial air gap. In the latter case, the armature comprises conductors mounted on an insulating disc disposed between two supports, one carrying the field coils and the other the permanent magnets; one of the supports may be angularly movable.