Patent GB-433277-A (GB)
Title: Improvements in commutators
IPC: H02K13/00
Filed: 1933-11-04
Abstract: 433,277. Commutator switching- arrangements. PLATEN, B. C. VON, 99, Ostermahnsgatan, Stockholm. Nov. 4, 1933, Nos. 30682 and 30683. Void [Abridged as open to inspection under Sect. 91 of the Acts, May 5, 1934]. [Class 38 (ii)] [See also Group XXXVII] In commutators for rectifying alternating currents or converting direct currents from one voltage to another, of the kind having a comparatively small number of segments, and in which the circumferential extension of the segments is considerably in excess of the corresponding dimensions of the brushes, each segment comprises a contact bar which is mounted on the commutator shaft through the intermediary of a supporting flange or disc extending substantially at right angles to the shaft, and consecutive segments are insulated from each other by air and solid material, the latter being so arranged that its shortest path of surface leakage is, at least at one point, nearer the centre than the inner face of the contact segment. The commutators are particularly suitable for arrangements of the kind shown in Fig. 1 for converting a low-voltage direct current supplied to terminals 1, 2 to a high voltage direct current delivered at terminals 3, 4. The arrangement includes primary commutators k1, k2, co-operating with windings l1, l2, on transformers T1, T2, secondary commutators K1, K2, co-operating with windings L1, L2, on the transformers, a generator G1, for supplying magnetizing currents to windings M1, M2 on the transformers, and a generator G2 for effecting current reversals in the windings l1, l2 when these windings are momentarily short-circuited. The magnetization of the generators G1, G2, is controlled by means of adjusting windings Q2, Q4, which receive current from relays R1, R2, controlled by impulses set up on faulty commutation between main brushes B1, b1 and auxiliary brushes B2, b2. The relays may be of the kind described in Specifications 388,061 and 392,950. By increasing the number of commutators, the system can be extended to four, six, or more phases. In a commutator construction for use with six phases, Fig. 5, each commutator unit consists of conducting segments 15, 16 with supporting flanges 17, 18 separated by an insulating ring 40 provided with flanges 20 to increase the surface leakage path between the segments. Additional insulating rings 23 separate adjacent units, and the shaft 19 carrying the units has a central flange 24 against which three commutator units are pressed on either side and clamped by nuts and washers. Insulating rings 28, inserted inside each supporting flange, and insulating sleeves 29, 30 serve to insulate all the flanges from the shaft. The rear edge of each segment is preferably made of an arc-resisting material, e.g. steel, tungsten or chromium. In another construction, Fig. 8, the commutator segments 94, 101 are made integral with supporting flanges 95, 102 and central bosses 99, 103, and have reinforcing ribs 96, 97, the two segments being respectively connected to slip rings 106, 105, all the conducting parts being insulated from the supporting shaft 98 by an insulating sleeve 100. In another modification the slip rings are in the form of discs with vane like projections carrying the commutator segments, the discs being separated by flanged insulating bushings. In another construction, Fig. 13, the supporting flanges 31 are of insulating material, and are provided with recesses 42 adjacent the spaces between the commutator segments 32, 41, the sides of the recesses being preferably provided with corrugations 43 to increase the surface leakage path. Where a large number of commutators are mounted on the same shaft, the commutators subjected to the highest voltages may be arranged in the middle. In the arrangement shown in Fig. 17 alternate commutator segments 122, 124, are connected to a slip ring 126, and the remaining segments 123, 125 to a slip ring 127. In this arrangement, the D.C. brushes 128, 129 co-operate with the slip rings, and the A.C. brushes 120, 121 with the commutator segments. Auxiliary segments 130 .... 133 alternately connected to auxiliary slip rings 134, 135 are provided for the withdrawal of deviation impulses. Specification 389,824 also is referred to.