Patent GB-424244-A (GB)
Title: Improvements in tap changing systems for electric transformers
IPC: H01H9/00
Filed: 1933-05-10
Abstract: 424,244. Transformers; automatic reversible motor regulators. WESTING- HOUSE ELECTRIC & MANUFACTURING CO., East Pittsburg, U.S.A.-(Assignees of Snyder, F. L.; 273, Euclid Avenue, Sharon, Pennsylvania, U.S.A.) May 10, 1933, No. 13620. Void [Abridged as open to inspection under Sect. 91 of the Acts, Nov. 27, 1933]. [Classes 38 (ii) and 38 (iv)] [See also Group XXXVII] A system of tap changing of a transformer winding without disconnection from the load comprises a selector switch connected with each of the winding taps A-I, alternate taps being connected together by bus bars 60, 62 and to either side of a preventive auto - transformer 17 to which the power circuit is connected, transfer switches X, Y disposed between each end of the autotransformer and one of the sets of winding taps, and a switch Z in shunt with the autotransformer. In changing from the position shown in Fig. 1 to the second position with tap B closed, switches B and Y are closed and shunting switch Z is opened to give the intermediate step. Then switches A and X are opened and the shunting switch Z to give the second position. In the intermediate position circuit 13 is influenced by the mean of the two voltages corresponding to positions A and B. In order to obtain the sequence of switch operations, the top and intermediate switches may be operated by cam members mounted on a common shaft which is driven by an electric motor. The operating members can be controlled either manually or automatically by the arrangement shown in Fig. 4 in which the operating motor 18 energized from the battery 24 is controlled manually by the switch 30 or automatically by the relay 33. The switch 30 controls actuation of the electromagnetic switches 28, 29 to move the motor in the desired direction. A switch 52 has two positions for determining whether the control shall be manual or automatic. If in the latter position, variation of the voltage in circuit 13 affects relay 33 to actuate either solenoid 35, 36 which control the direction of operation of motor 18. A timing relay 37 introduces a time delay between successive operations of the taps. The intermediate and shunting switches are of the quick break oil circuit type shown in Fig. 8 and comprise fixed contacts 100 mounted on porcelain, and a movable assembly 122 provided with a guide member 105 engaging a porcelain bushing 106. Each switch is mounted on arms 120 pivoted to brackets 124 and is moved by a pivoted lever 117 which is actuated by a cam member 125 the switches being alternately opened and closed. The cam member is rotated by bevels 186 engaging a bevel 187 on the operating shaft 84. The movable contact assembly 122 comprises a main member 143 and an arcing tip 144 which is constrained by a compression spring to open contact after the main member. The spring then accelerates the contact breaking to reduce arcing. The movable contact assembly 122 is connected by a flexible conducting member 159 to the terminal and guide member 106. The casing containing the switches is filled with oil to the level 132. The selector switch assembly, Fig. 15, comprises contact arms 90, 92 mounted on toothed ring members 94, 95 which are alternately actuated by a rotating pinion 96 mounted on the shaft 128. The contact arms are mounted on conducting discs 217, 218 suitably insulated from their shafts 220, 221. Electrical connection of the external conductors is made by brushes 225, 226 bearing on the discs. Suitable gearing determines the relative speeds of the switch operating shafts.