Patent GB-1026532-A (GB)
Title: Improvements in or relating to voltage or current regulator apparatus
IPC: H02M5/12
Filed: 1961-05-15
Abstract: 1,026,532. Transformers. BRENTFORD ELECTRIC Ltd., and M. G. J. FRY. May 11, 1962 [May 15, 1961], No. 17646/61. Heading H1T. [Also in Division H2] Voltage or current control is effected by connecting in series a variable number of transformer secondary windings or other A.C. sources by switching group arrangements such as groups of silicon controlled rectifiers or of saturable reactors having square loop cores which are so associated with each winding or source that any combination of windings or sources can be connected in series in the output circuit, those not so connected being bypassed but not short circuited. The apparatus may operate as a rectifier or inverter, as a variable ratio transformer or as a variable voltage arrangement of transformers in series, parallel or cascade connection. The voltages produced by the windings may be in geometric progression, Fig. 1, shows a transformer with a number of secondary windings 2a-2g each having in series with it a group of two parallel connected oppositely poled silicon controlled rectifiers 3a, 4a-3g, 4g and a similar pair of rectifiers 5a, 6a-5g, 6g in parallel with it. By repeatedly triggering one pair associated with each winding so that it provides a full wave conducting path the winding can be connected in series in circuit 7a, 7b if the rectifiers triggered are in series with the winding or can be bypassed if they are connected across it. The pairs of rectifiers are triggered, as required, by pulses provided substantially at current (or voltage) zero points by a saturating transformer 8 (Fig. 1) through lead 14 and gating devices indicated at 9a-9g which are controlled by a reversable binary digital counter, the voltage output being increased or decreased by causing the counter to add or subtract. In the gate circuit used (Fig. 2, not shown) the reversible voltage from the counter lead 11a enables, according to its direction, either pulse transformers 19 and 20 or transformers 21 and 22 to pass pulses fed in through lead 14 and so trigger either rectifier 3a, 4a, or rectifier 5a, 6a. In an alternative arrangement (Fig. 3, not shown) each pair of controlled rectifiers is replaced by a group consisting of a rectifier bridge with a silicon controlled rectifier connected across one diagonal. By using centre taps on the windings or a different arrangement of the rectifier groups (Fig. 7, not shown) a full range of output voltages of either polarity may be obtained. If an extra secondary winding 38 producing a voltage equal to the sum of the voltages of the switchable secondaries is connected in the circuit the range of voltage variation may be doubled. Converting.-By arranging for suitably triggering the rectifier groups associated with each secondary winding 42 (Fig. 12) a full wave rectified output may be obtained the polarity depending on whether the triggering pulses are provided dy transformers 52 and 54 or by 53 and 55. Fig. 13 shows an inverter arrangement in which the secondary 58 of a multi-winding transformer is connected through controlled rectifier groups 59, 60 and 61, 62 and an autotransformer 63 to a D.C. supply at 65. The D.C. voltage at 65 is higher than the peak voltage induced in winding 58 by the A.C. supply and the rectifier groups are triggered when the D.C. and A.C. voltages are in opposition. As each rectifier begins to conduct transformer 63 produces a voltage which switches off the rectifier which is already conducting. By using a variable number of secondary winding and rectifier groups with their D.C. terminals 65 connected in series the flow of energy from the D.C. to the A.C. mains can be controlled.