GB1438920A - Brushless dc electric motors - Google Patents

Abstract

1438920 Electric motors SOC D'APPLICATIONS GENERALES D'ELECTRICITE ET DE MECANIQUE 9 May 1974 [18 May 1973 26 July 1973 29 March 1974] 20478/74 Heading H2A In a brushless D.C. motor comprising a stator winding 10 disposed in a planar air gap between two toothed rotor polepieces 15, 16, the polepieces being oppositely magnetized by a coil or a magnet 18 disposed radially with the winding 10, the winding 10 comprises 2n groups of radial conductors, where n is the number of teeth on each rotor polepiece, successive groups carry current in opposite directions, and all groups are embedded in an annulus 11 of moulded insulating material, the motor further comprising a rotor position sensor offset by 90 degrees electrical from the groups of radial conductors. The field coil or magnet 18 may be mounted on the rotor, as shown, or on the stator, Fig. 10 (not shown). The rotor polepieces are made of solid, non- laminated ferromagnetic material. Each polepiece shown has four teeth. The stator winding 10 may have four flat coils, each group of radial conductors then comprising one coil side. There may, alternatively, be eight flat coils, adjacent coils being wound in opposite directions, and each group of radial conductors then comprises the juxtaposed coil sides of two adjacent coils. The rotor position sensor shown is a pick-up winding comprising flat coils whose coil sides are offset by 90 degrees electrical from the groups of radial conductors of winding 10. The pick-up winding may be disposed to respond to stray flux, as shown, and Fig. 4 (not shown). Alternatively, it may be mounted in the same plane as winding 10 to respond to the main rotor flux, Figs. 5, 6, 7 (all not shown).