Patent GB-446890-A (GB)
Title: Improvements in or relating to tapping switches or ratio-adjusting devices for electrical transformers
IPC: H01H9/00
Filed: 1934-07-31
Abstract: 446,890. Transformers. NEEP, G. H., c /o Switchgear & Cowans, Ltd., Elsinore Road, Old Trafford, Manchester, and ROWBOTHAM, J. L., c /o Hackbridge Electric Construction Co., Ltd., Hersham, Walton-on-Thames. July 31, 1934, No. 22266. [Class 38 (ii)] [See also Group XXXVII] A transformer tapping switch comprises a driving shaft G formed with a worm F engaging with a wheel E on a shaft D. The portion of the shaft D to the left of the wheel E is of square section and has mounted on it a double helical cam K which rotates with the shaft D and is moved axially along the shaft during rotation by the action of fixed racks l, L engaging the double cam K. Mounted on a pair of frame bars B are fixed contacts M connected respectively to the odd number tappings of the winding and similar contacts m mounted on bars b are connected to the even number tappings. Spring contact fingers N, n are mounted on pairs of frame bars C, c and have rollers N<5>, n<5> which are engaged successively by the double helical cam K to move the contact fingers into engagement with their respective fixed contacts M, m, so as to connect the corresponding tapping points to bus bars O, o. The shaft D also carries a pair of cams P, p adapted to operate a pair of auxiliary contact fingers S, s into engagement with corresponding fixed contacts R, r. The construction of the cams P, p is shown in Fig. 4. The cam P is laterally slotted and in the slot is mounted a pair of flicker plates p<2> pivoted at <p3> and forced apart by a spring p<4>. Assuming the cam to be rotating in a clockwise direction, the roller on the contact finger rides up the right hand slope of the cam and the right-hand flicker plate yields. The roller then rides along the circumference of the cam and of the left-hand flicker plate until it reaches the corner when the flicker plate yields suddenly allowing the switch to open rapidly. Flicker plates of somewhat similar construction are fitted to the double helical cam K. The worm F also drives a wheel H attached to the rotor of an induction regulator of the kind described in Specification 263,615, [Class 38 (ii)]. Fig. 8 is a diagram of the connections in which X is the tapped winding and Y the induction regulator, the outgoing lead being shown connected to the first tapping. To change to tapping 2 the shaft D is driven round and the cam K engages the contactor n associated with tapping 2 and moves it into engagement with its fixed contact thus making connection with tapping 2. The cam P then opens the switch S so that the whole current passes through the induction regulator Y. The regulator is simultaneously adjusted so that the voltage of the outgoing lead is the same as that of tapping 2. The cam p then closes switch s to provide a path for the current round the induction regulator. Then the rear edge of the helical cam K disengages switch N to disconnect tapping 1. Reference has been directed by the Comptroller to Specifications 4275<*> /03, [Class 38], 15878/15 and 292,037, [both in Class 38 (v)], and 365,699, [Group XXII].