Patent GB-681161-A (GB)
Title: Improvements relating to electric step-by-step control or indicating systems
Inventor: PEEL ROBERT FREDERICK CRESWELL
IPC: G05D3/12
Filed: 1949-06-03
Abstract: 681,161. Electric follow-up control systems. METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. May 16, 1950 [June 3, 1949], No. 15022/49. Class 40 (i) [Also in Group XXXV] In a step-by-step control or indicating system for operating e.g. on-load tap changing transformers, wherein master and follower switches have plural interconnected fixed contacts, the master has a single moving contact, and the follower has two moving contacts normally positioned one on each side of a fixed contact corresponding to that engaged by the master moving contact so that a displacement of the master moving contact through one step completes a motor control circuit through the appropriate follower moving contacts to displace the latter together through one step in correspondence with the displacement of the master moving contact, the number of inter-connecting lines is reduced by sequentially grouping corresponding fixed contacts of each of the switches according to the operational cycle and connecting the groups appropriately to lines which are less in number than the fixed contacts, e.g. by connecting the 1st, 4th, 7th, &c. fixed contacts to the 1st line, the 2nd, 5th, 8th, &c. contacts to the 2nd line and the 3rd, 6th, 9th, &c. contacts to the 3rd line. In a modification the master and follower switches may have circularly disposed fixed contacts equal in number to the line wires and to the moving contacts but less than the number of operating positions of the system, which engage the fixed contacts in a stepping sequence over a plurality of revolutions. In Fig. 2 the fixed contacts 1 to 11, 1<SP>1</SP> to 11<SP>1</SP> of master and follower switches MS1, MS2 are connected in three sequential groups to three line wires x, y, and displacement of the master moving contact b from e.g. contact 6 to contact 5 or 7 by a controlling tapchanger energizes an A.C. motor M through follower moving contacts a, c, follower fixed contacts 5<SP>1</SP>, 7', and limit switches LS1, LS2 to drive the follower contacts and the controlled tapchanger together over one step to rest on contacts 6<SP>1</SP>, 8' or 4<SP>1</SP>, 6<SP>1</SP>, and break the motor circuit. Plural follower switches and controlled tapchangers : are controlled from a single master switch Fig. 3 (not shown) and when a follower switch has been driven through the step selected by the master switch, a secondary moving contact disposed between the two primary contacts energizes a relay to de-energize the associated motor and prevent further spurious stepping through the circuits of the remaining follower switches if all the latter do not operate simultaneously. In Fig. 4 a master switch RMS1 has three radial 120 degrees spaced contacts ar<SP>1</SP>, br<SP>1</SP>, cr<SP>1</SP> rotatable together over slip rings 1', m', n' and three correspondingly spaced fixed contacts 1r<SP>1</SP>, 2r', 3r' connected over lines x, y, z to similarly disposed fixed contacts 1r<SP>2</SP>, 2r', 3r<SP>2</SP> in a follower switch RMS2, traversed by three contacts ar<SP>2</SP>, br<SP>2</SP>, cr<SP>2</SP>, rotatable together over slip rings l<SP>2</SP>, m<SP>2</SP>, n<SP>2</SP> by an A.C. motor M connected through limit switches to slip rings l<SP>2</SP>, m<SP>2</SP>. An A.C. supply is connected to the centre tap of the follower motor winding and to the slip ring n<SP>1</SP> of the master switch. Normally, master switch moving contacts ar<SP>1</SP>, br<SP>1</SP>, cr<SP>1</SP> respectively rest on fixed contacts 1r<SP>1</SP>, 2r', 3r' and follower switch moving contacts ar<SP>2</SP>, br<SP>2</SP>, cr<SP>2</SP>, respectively rest on fixed contacts 1r<SP>2</SP>, 2r<SP>2</SP>, 3r<SP>2</SP> so that the motor is de-energized and at rest, while displacement of the master switch moving contacts over-one tapchanging step energizes the motor over lines x or z to rotate the follower moving contacts and controlled tapchanger through a corresponding step so that the motor is again de-energized. The follower switch and controlled tapchanger may be successively stepped thereafter in correspondence with further rotation of the master switch by the controlling tapchanger through successive steps comprising a plurality of revolutions.