COMMUTATORS

A commutator for an electric motor-generator comprises two opposed commutator elements (3, 4) each providing a continuous circumferential conducting surface (5, 6), to which a DC supply is connected via supply brushes (18, 19). A conductive commutation segment (7, 8) projects axially from each commutator element (3, 4). Two neutral, freewheeling segments (9, 10) are positioned between the commutation segments (7, 8) and insulated from the commutation segments by insulation rings (11). The freewheeling segments (9, 10) are electrically connected together via a high-resistance commutation ring (23). Three winding brushes (20, 21, 22) are located (120) degrees apart about the commutator. Each brush (20, 21, 22) engages alternately with the commutation segments (7, 8) and freewheeling segments (9, 10) as the commutator rotates. As each brush (20, 21, 22) moves from a commutation segment (7, 8) to a freewheeling segment (9, 10), the presence of the commutation ring (23) connecting the two freewheeling segments serves to inhibit sparking between the brush (20, 21, 22) and the commutation segment (7, 8). The angular position of the brushes (20, 21, 22) is adjusted by means of an arrangement of two electromagnets, supplied with the motor current, and two permanent magnets, such that the phase of the DC voltage supplied to the windings is matched to the load. Alternatively, a plurality of brushes are provided for each phase, such that the winding current passing through each brush is reduced, thereby to reduce resistive losses. Commutateur pour générateur-moteur électrique, comprenant deux éléments de commutateur opposés (3, 4) qui présentent chacun une surface conductrice circonférentielle continue (5, 6), à laquelle une alimentation C.C. est reliée par des balais d'alimentation (18, 19). Un segment de commutation conducteur (7, 8) ressort axialement de chaque élément (3, 4). Deux segments libres neutres (9, 10) se trouvent entre les segments de commutation (7, 8) et son isolés d'eux par des bagues d'isolation (11). Les segments libres (9, 10) sont reliés électriquement via une bague de commutation haute résistance (23). Trois balais à enroulement (20, 21, 22) se trouvent écartés à 120 degrés du commutateur. Chaque balai (20, 21, 22) s'enclenche alternativement avec les segments de commutation (7, 8) et les segments libres (9, 10) à mesure que le commutateur entre en rotation. A mesure que chaque balai (20, 21, 22) se déplace d'un segment de commutation (7, 8) ver