Patent GB-364821-A (GB)
Title: Improvements relating to electrical transformer tap-changing apparatus
IPC: H01H9/00
Filed: 1930-12-23
Abstract: 364,821. Motor control systems ; regulating switches. DIGGLE, H., 67, South Grove, Brooklands, Cheshire, GLOVER, K. G., Porthcurnow, Denstone Road, Davyhulme, near Manchester, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Dec. 23, 1930, No. 38780. [Classes 38 (iii) and 38 (v).] In means for mutually controlling a pair of transformer tap changers, an auxiliary switching system is provided whereby in the event of the tap changers becoming out of step the motor controlling one of the tap changers is brought into operation to restore the desired condition. The motors M1, M2 for the two tap changers (not shown) are each provided with "forward " and " reverse " fields MF1, MR1, MF2, MR2, and a brake B1, B2 controlled in a conventional manner by operating coils FC1, RC1, FC2, RC2 the circuits of which may be completed when it is desired to initiate tap changing by " raise " and " lower " pushbuttons R1, L1, R2, L2. Corresponding buttons of the two tap changers are interlocked for simultaneous operation, and holding circuits completed by cam-operated contacts C1, C2 associated with the tap changers so as to be closed during transfer from one tap to the next are provided. The auxiliary switching system comprises a switch S having a movable contact 13 coupled to the movable element of the tap changer associated with the upper control system so as to connect a contact bar 12 with that one of a set of contact studs 1 .. 11 corresponding to the setting of that tap changer. These studs are connected to a set of contacts 21 .. 31 on a second switch AS that comprises also a pair of movable contacts 32, 33 coupled to the movable element of the tap changer associated with the lower control system and interconnected electrically with that system as shown. The arrangement is such that as the second-mentioned tap changer is operated from one tap to the next, one of the contacts 21 .. 31 breaks connection with one of the contacts 32, 33, and as the tap changer moves to the succeeding position, the first-mentioned contact engages the other of the contacts 32, 33. Thus, whenever the two tap changers are at different settings, either the " forward " or the " reverse " control circuit of the lower system is completed in accordance with which of the contacts 32 or 33 is in a position to establish connection through to the stud engaged by the contact 13. Thus tap changing is caused to proceed in the lower system until the contacts 32, 33 arrive at a position where they fail to connect with the fixed contact that is connected to the stud engaged by the contact 13, in which position the two tap changers have similar settings, and the control circuit is accordingly broken. As shown in Fig. 3, the contacts 21 .. 31 of the switch AS are in the form of curved blades mounted around the periphery of a fixed disc 34 having a projecting centre pin on which is rotatably mounted a second disc 45 coupled to the tap changer (not shown). The second disc carries the two movable contacts 32, 33 which are in the form of rings from each of which an inclined tang 50, 51 projects. Thus as the disc 45 rotates with the tap changer, the contacts 21 .. 31 are transferred in turn first from one ring into the gate between the tangs 50, 51 and then on to the other ring. Connections to the rings are made respectively through the centre pin to the outer ring and through a spring-urged contact 52 to the inner ring.