Patent GB-471587-A (GB)
Title: Improvements in and relating to electric transformers
IPC: H02M1/04
Filed: 1936-02-03
Abstract: 471,587. Converting; transformers. BRITISH THOMSON - HOUSTON CO., Ltd. Feb. 3, 1936, No. 3227. Convention date, Feb. 1, 1935. [Class 38 (ii)] A transformer for obtaining peaky potentials of adjustable phase comprises a core 11 having spaced arms 15, 16 connected at one end by a yoke 13 which may be subjected to a controlling magneto-motive force. A pair of bridging members 17, 18 forming parallel magnetic paths are arranged between the arms 15, 16 and each has, on either side of an intermediate portion a portion 20, 22 of variable reluctance and a portion 19, 21 of constant high reluctance. The relative positions of these portions are reversed in the two members 17, 18 and a connecting member such as 23, 24, 25 is arranged between the intermediate portions of the bridging members and carries primary and secondary windings, the arrangement being so designed that peaked voltages induced in the secondary winding are varied in phase in response to variations in the controlling M.M.F. on the core. In a modification, one of the bridging members 17, or 18 may be magnetically symmetrical by having both the portions on either side of the intermediate portion either of variable reluctance or of constant high reluctance. The portion of variable reluctance is provided by a portion of reduced cross-section and that of high constant reluctance by an air gap. Saturation effects in the connecting member 23 produces the peaked potentials and changes in the controlling M.M.F. alter the magnetic potential between the bridging members (due to their asymmetry) so as to vary the phase of the peaked voltages. Peaking transformers as above are used, Fig. 1, to supply grid control potentials to a rectifier arrangement in accordance with the output direct current so as to maintain this constant. The rectifier comprises two banks 37, 38 of full wave rectifiers connected in series and supplied from a transformer 40. Each rectifier bank has its peaking transformer which is adapted for three phase working and has its controlling M.M.F. provided by a coil 26 in series in the D.C. circuit. Phase shifting transformers 64 and current limiting impedances 68-70 may be provided in the grid supply circuits. Only one set of valves in each bank may be grid controlled although for combined rectifier and inverter operation both sets must be controlled. The peaking transformers in each bank may be arranged to balance at slightly different current values. The Specification as open to inspection under Sect. 91 disclosed a transformer arrangement having only one bridging member having a variable reluctance part and a constant high reluctance part on each side of an intermediate portion. The intermediate portion was joined to the yoke member by a connecting member carrying primary and secondary windings and the winding on the yoke providing the controlling M.M.F. was split and arranged on either side of the middle part of the yoke. An arrangement was also described, Fig. 2 (Cancelled) in which a peaking transformer 81 comprising primary and secondary windings 27-32 arranged on saturable bridging members 23, 24, 25 controlled an arc converter 37. A winding 26 produced a polarizing M.M.F. in accordance with the D.C. load and a further winding 82 supplied from a constant current D.C. generator 83 produced on opposing M.M.F. so that the phase of the peaky potentials was varied in accordance with the unbalance of the two M.M.F's. so as to control the output D.C. of the converter. This subjectmatter does not appear in the Specification as accepted.