Patent GB-269156-A (GB)
IPC: H01H9/00
Filed: 1927-03-24
Abstract: 269,156. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Dann, W. M., Knotts, C. L., Thompson, A. W., and Hill. L. H.). April 12, 1926, [Convention date]. Regulating transformers. - Relates to means for changing the tap connections of transformers, and comprises a transformer in which the low tension winding is in two sections normally connected in parallel, provision being made for disconnecting the sections in turn while tap changing is being effected. Tap changing is effected by a shaft adapted to make one revolution for each change, the shaft being selectively driven by hand or by a motor for which a pushbutton control system is provided. Various indicating and protective arrangements for the transformer are also provided. The transformer, contained in a tank 1 provided with cooling coils 8, has a manually-operated tap changer 4 on the high tension winding 102, and its low tension winding consists of two portions 104, 105 connected in parallel to the line through circuit breakers 74, 75. The windings 104, 105 are provided with tappings connected to two groups 14 - - 22 and 15 - - 23 of switch contacts adapted to be closed a pair at a time by cams 28 on a shaft 13 so geared to a shaft 7 that one complete revolution of the later changes the pair of tap connections in use. The shaft 7 is provided with cam mechanism 83, Fig. 3, for operating the circuit breakers 74, 75, in such a manner that the winding sections 104. 105 are withdrawn from circuit in turn while their tap connections are being changed, both winding sections being left in circuit when the operation is completed, i.e. after a complete revolution of the shaft 7. The latter is formed with a squared portion 41, Fig. 7, on which is mounted a dog clutch 43, 44 which may be caused to lock to the shaft one or other of a pair of wheels 45, 46 driven by worms 47, 48 on shafts 32, 36 adapted for motor 'and manual operation respectively. Manual operation is effected by means of a handle 35 on the shaft 36, and stopping is effected at the end of each revolution by means of a spring- urged lug 53, co-operating with a notch in the periphery of a stop wheel 51. The lug 53 may be withdrawn from the notch by pressure on a handle 64 causing a. member 57 to turn on its pivot 62 and bear on a pin 55. The member 57 is connected to a lever 37 by means of which the dog clutch 43, 44 is operated so that when the latter is shifted to engage the motor drive, the member 57, after being raised by the handle 64, is moved to the right and holds the lug 53 in its withdrawn position. A disc 69 rotated through gearing 67 and bearing index marks cooperating with a pointer 72 is provided to indicate the tap connections in use. The shaft 7 is extended rearwardly to afford means for operating pilot switches 92 - - 96 forming part of the control gear for the motor 31 which drives the shaft 32. The shaft 7 is also connected through gearing to a shaft 101 which operates limit switches 98, 99 arranged to prevent further operation of the motor in one direction when the last of the series of tap connections is in use. The motor, which is provided with a magnetic brake 33. is supplied from a two-phase source of current A - - D, Figs. 12, 13 and 14, and its movement in a forward direction is controlled by a series of contactors 202, 204, 210. 220, the closing of which is initiated by depressing the " forward " push button on the operator's panel, Fig. 12. A similar set of contactors 203, 205, 211, and 221 operating in response to depression of the " reverse " push button is provided for controlling reverse movement of the motor. The contactors are energized from the phase C, D through a disconnecting switch .201, and their circuits are connected through the appropriate pilot switches 92 - - 96 and limit switches 98, 99 so as to disconnect the motor when the shaft 7 has made the single revolution necessary to effect a change of tap connections, and to prevent further movement in the same direction when the limiting connection has been made. Tb prevent damage in the event of simultaneous operation of the " forward " and " reverse " push buttons, the circuits of the " forward " contactors 210, 220 are taken through back contacts 229 on the " reverse " contactor 221, and the circuits of the " reverse contactors 211, 221 are taken through back contacts 228 on the " forward " contactor 220. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the provision on the operator's panel of a temperature indicator 120 connected to the low tension winding of the transformer by a current transformer 121 and to an indicator forming part of a Wheatstone bridge 126 supplied with direct current from an auxiliary source 401. 402. This subject-matter does not appear in the Specification as accepted.