Patent GB-464118-A (GB)
Title: Improvements in and relating to methods of regulating vapour electric converters and the like apparatus
IPC: H02M1/04
Filed: 1935-07-04
Abstract: 464,118. Converting. BRITISH THOMSON-HOUSTON CO., Ltd. July 4, 1935, No. 19151. Void. Convention date, July 4, 1934. [Class 38 (ii)] In a polyphase converting arrangement employing an interphase transformer, regulation is obtained by varying the phase angle between the voltages applied to anodes which are conducting simultaneously. By this means voltages such as #3/2 and ¢ of the maximum can be obtained at a power factor of unity. Voltages intermediate these can be obtained by delay of ignition. Since the effective voltage is proportional to the vector sum of the alternating voltages applied to the anodes conducting simultaneously a variation in phase results in a variation of the effective voltage. Fig. 2 shows a double - six - phase arrangement. When normal double-six-phase working occurs with ignition at the points A, B, &c., the maximum output voltage corresponding to the curve A, B, C, &c. will be obtained. By blocking three anodes in each group so that double-three-phase working occurs, a voltage proportional to #3/2 maximum and represented by the curve A1, A, B1, B, &c. will be obtained., This will be at unity power factor. Overheating of the conducting anodes is prevented by a periodic change-over of the active anodes in each group. A voltage ¢ maximum at unity power factor and represented by the curve ea; fb; ac, &c. can be obtained by allowing anodes f, b in each group to conduct between t1 and t2, transferring at t2 to anodes a, c in each group and so on. Regulation between max. and #3/2 max. is obtained as follows: If ignition of only one anode in each group is delayed the voltage curve will be F, F11, F10, G, All, A10, &c. Delay of ignition of both anodes in each group gives a voltage curve A, A6, A7, B, B6, &c., the voltage being variable between max. and #3/2 max. Voltages between #3/2 and ¢ max. are obtained by delay of ignition of the three anode in each group that are operative. This gives a voltage curve A9, B8, B9, C8, &c. This gives regulation down to a voltage ¥ max. corresponding to the point D3. Regulation between i and ¢ max. is obtained by operating as for ¢ max. voltage but allowing one anode in each group to conduct earlier. This gives a curve D3, C14, C15, E3, &c. Regulation below ¢ max. is obtained as follows: At the point t18 anode c in one group and anode d in the other group conduct. At the point t19 anode c transfers current to anode a. This gives a voltage curve D20, D18, A19, E19, &c. having unity power factor at zero voltage. The curves at the lower part of the Figure show the conditions for inverter operations. The Specification describes modifications for arrangements having 4-three-phase windings with interphase transformers and 6-two-phase windings with interphase transformers. In a modification, instead of the two groups being paralleled through an interphase transformer they may be connected in series. A frequency changer is described consisting of two double six-phase arrangements in recumbent-8 connection. The half-wave in each group for a 3-1 frequency reduction is formed by the solid curve A, B, C, D, E, F, G, H, I, Fig. 11 ; and for a 2 : 1 frequency reduction the dotted curve J, B, C, E, F, K, L.