Patent GB-191219000-A (GB)
Title: Improvements in or relating to Means for Converting Electric Currents.
Inventor: BULLOCK ARTHUR ROBERT
IPC: H02M1/22
Filed: 1912-08-19
Granted: 1913-08-19
Abstract: 19,000. Bullock, A. R. Aug. 19. Commutator switching - arrangements. - To avoid sparking, condensers are connected in parallel across the breaks made between the co-operating poles of an alternating-current circuit and a direct-current circuit by the operation of a commutator. The commutator may be divided into two parts, one having a greater peripheral speed than the other. The commutator device shown in Fig. 1 is of the usual kind, segments being connected together in groups for connexion to slip-rings. Condensers 16, 17 are connected between the poles of the co-operating circuits 12, 13 and 14, 15, and a condenser 18 across the brushes of the commutator. The brush-holders are carried by splitrings 7, which are clamped about a flange 6 secured to the carcase of the driving-motor 3; and by varying the number of brush-holders in use and their angular position in conjunction with the use of a suitable number of slip-ring brushes, polyphase currents may be dealt with. Fig. 5 shows another arrangement of condensers 25, 26, 27, 28, which are connected in a closed polygon, opposite corners forming the terminals of the direct-current circuit, and the remaining corners the terminals of the alternating-current circuit. A condenser 33 may be connected across the terminals of the direct-current circuit. Fig. 6 shows two commutators 39, 40 mounted upon a common shaft 38. The former has the greater diameter and upon it the converting connexions are broken, whilst upon the commutator 40 they are made. The brushes of the commutator 39 are carried upon a sleeve 44 as described above; the brushes of the commutator 40 are mounted on a ring 53, which may be turned within a groove in a fixed standard. The commutator 40 has four groups of segments, see Fig. 9, 58 connected to 60, and 59 connected to 61; brushes 54, 55 of any good conducting material are set at an angle of 90 degrees and co-operate with the groups of segments; other brushes 56, 57, also spaced 90 degrees apart and set opposite to the brushes 54, 55, are usually of carbon, and are connected by resistances 66, 67 to the brushes 54, 55 respectively. The commutator 39 has four groups of segments, 62 connected to 64, and 63 connected to 65; two sets of brushes 47, 48, of carbon and set at an angle of 90 degrees, co-operate therewith. The connexions between the commutator segments of the two commutators and of the commutator device and condensers to the alternating and direct current circuits 12, 13 and 14, 15 are shown in Fig. 9. Variable resistances 68, 69 may be used to prevent sparking when the circuits are made on the commutator 40. The arrangement of the brushes with respect to the different groups of commutator segments is such that the brush 56 makes contact just in advance of the brush 54, while the brush 48 makes contact last. The " make " is thus effected through a carbon brush and resistance, and the " break " upon a rapidly moving surface with a carbon brush, while a brush of good conductivity carries the main current.