Patent GB-871306-A (GB)
Title: Control of rectified current electric locomotives
IPC: B60L9/12
Filed: 1959-10-26
Abstract: 871,306. Transformers. FORGES ET ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE JEUMONT. Oct. 26, 1959 [Oct. 28, 1958; Dec. 15, 1958], No. 36175/59. Class 38 (2). [Also in Group XXXVII] In a motor operated tap-changing system for supplying rectified current to traction motors M1, M2, the contactors 11A-19A, 21A-29A. and 11B-19B, 21B-29B connecting with tappings on the symmetrical secondary winding parts SA and SB and on the reversible booster windings SA1, SA2, SB1 and SB2 are operated off load and are prevented from operating under load by protective relays 31B, 31A, 33, 32B, 32A and 34. By the use of different amounts of positive and negative boost twentythree different voltages are obtainable from each side A and B. In normal operation at a given voltage all the rectifiers IA, IIA, IB, IIB conduct. When the voltage is to be changed, e.g. by using contactors 19A and 29A instead of 18A and 28A the appropriate rectifier IA is first biased negatively and extinguished, the load on side A transferring to rectifier IIA. Contactor 18A is then opened and 19A is closed and the same cycle is then followed with rectifier IIA and contactors 28A and 29A. Positive bias ensuring operation of rectifiers IA, IIA, IB, IIB is supplied from rectifier source R2 through opposing coils of differential relays 33, 34. Step-by-step rotation of the auxiliary motor 37 (Fig. 2), is started by operation of controller 39 to open the appropriate contactor provided all the rectifiers are in operation and consequently the relays 33, 34 are in the off position, and provided also that the relays 31A, 31B, 32A 32B are energized indicating that the negative bias circuits are in good order. These latter circuits are supplied from rectifier R1, the currents passing through the protective relays so that in normal operation of the rectifiers their contacts in starting circuit 35 supplying the auxiliary motor 37 are closed. The auxiliary motor on starting opens the appropriate contact 1A whereupon rectifier IA is biased negatively and extinguished, the upper coil of relay 33 is de-energized and contacts 33B then close an operating circuit 36 for the auxiliary motor. The motor then opens and closes the appropriate contactors, e.g. 18A and 19A and subsequently closes 1A again to re-establish operation of rectifier 1A. The motor then continues to rotate to perform the same cycle with the appropriate contactors associated with rectifier IIA and may continue similar operation in relation to the rectifiers IB and IIB. If for any reason the auxiliary motor fails to move on to open and close the appropriate contactors the holding circuit of the main circuit-breaker is opened by a guard relay. Fig. 2 shows auxiliary motor 37 arranged to produce step-by-step operation of multi-contact switches 42, 44, 50, 51, 53 and 54. Of these 42 and 44 operate the auxiliary contactors 1A, 1B, 2A, 2B, control the succession of operations, produce stoppages at the end of travel, control energization of the rectifiers (if of " excitron " type) and control reversal of the motor fields &c. Multi-contact switches 50-54 comprise respectively the contactor selectors of booster windings SA1, SB1 of booster windings SA2 and SB2, and the contactor selectors 11A-14A with 11B-14B and 21A-24A with 21B-24B. The multicontact switches are driven through discs with suitable notches to obtain the correct amounts and sequence of rotation. The differential relays may be replaced by ordinary relays which may control different permissive circuits (Figs. 3 and 4, not shown). The rectifiers may be of the excitron or ignition types.