Patent GB-418507-A (GB)
Title: Transformer tap changing switches
IPC: H01H9/00
Filed: 1933-03-23
Abstract: 418,507. Transformers; regulating- switches. THOMAS, B., and THOMAS, E., 34, Worsley Street, Hulme, Manchester. March 23, 1933, No. 8736. [Class 38 (ii).] A single or multiphase on-load transformer tap-changing switch has one or more sets of contacts each set corresponding to a separate phase winding and comprising a movable main contact connected through a movable reactance to a movable pilot contact, the contacts being movable either together or in alternate steps by a pin and slot operating mechanism with which a locking mechanism is incorporated. The movable contacts of each set co-operate with a set of fixed contacts, connected to tappings on each side of a break in one phase winding of the transformer the main movable contact being adapted to bridge adjacent pairs of fixed contacts in succession when tap changing takes place, to alter the transformation ratio. To effect tap-changing the pilot contact 27, Fig. 1, is moved from the position shown in chain lines to make contact with contact 2. The main contact shoes 23, which are connected to 27 through the reactance 30 to prevent short circuiting of sections of the transformer winding, are then moved to break contact with 3 and bridge contacts 4 and 2. Further tap changing is effected in a similar manner. The main contact shoes 23, the reactance 30 and the pilot contact 27 are carried by spindles 22, 21, Fig. 2, through insulation 26, 29 the spindles 22, 21 being connected to slotted sectors 41, 40 respectively. Alternate movement of the main contact shoe and the pilot contact is effected through a crank shaft 43, journalled in the bearing 44 and carrying crank pins 45, 46. Rotation of the shaft 43 causes crank 45 to engage a slot 42 in the sector 40 producing through the shaft 21 the required movement of the pilot contact 27 and a corresponding movement of the reactance 30 which is carried by the shaft 21. During movement of the sector 40 the sector 41 is locked by means of an arc-shaped tongue 48 formed on the crank web concentric with the crank shaft, which passes through notches 50 in the lip 49 on sector 41. The sector 40 is similarly locked by means of a tongue 47 when the crank 45 releases it while the crank 46 engages with the sector 41 and produces through the shaft 22 the required movement of the main contact shoes 23. Further rotation of the crank shaft 43 produces repetition of the above described operations and causes further tap changing to be effected. If the switch is to be arranged for multiphase working the shafts 21, 22 may be provided with arms 21A, 22A and reactances 30 equal in number to the number of phases and the fixed contacts connected to the tapping points of the various phase windings may be arranged in a circle in a common oil tank 63. If desired several switches mechanically coupled and arranged in separate oil tanks may be used. In a modification (Fig. 3, not shown) the main and pilot contacts may be arranged to move together in which case only one spindle and one slotted sector are required. The tap changing switch may be operated by hand or by remote or automatic control.