Patent GB-996196-A (GB)
Title: Regulated power supplies
IPC: G05F1/34
Filed: 1961-08-22
Abstract: 996,196. Automatic control of current and voltage. AIR REDUCTION CO. Inc. Aug. 22, 1961 (Aug.22, 1960], No. 30240/61. Heading G3R. [Also in Division H3] A regulated power supply for a load such as a welding arc or a motor comprises a D.C. input source which feeds the load over a magnetic amplifier/rectifier combination, the magnetic amplifier being controlled by a feedback path in response to load conditions. As shown, load terminals 114,116 are supplied from the secondary windings 41, 43, 45 of a polyphase power transformer by way of the load windings such as 79 of a magnetic amplifier constituted by saturable reactors 71 to 76 and over rectifiers 81 to 86. The control windings, such as 80, of the saturable reactors are supplied by flux-resetting secondary windings 61 to 66 of the power transformer and are connected to a control line 338 by way of current limiting resistors 101 to 106, rectifiers 91 to 96 and transistors 342, 340. To ensure that re-setting of the magnetic amplifier takes place, even when the load becomes open-circuited, a stand-by setting circuit is provided in shunt with the load, this circuit including the load windings of the magnetic amplifier and auxiliary rectifiers 131 to 136, a positive line 138 and a negative line 140, artificial load resistors 141 to 146 and associated diodes 151 to 156. A feedback signal proportional to load current or load voltage, derived respectively from potentiometers 112 and 124, is applied over a selector switch 196 and a line 126 to a differential amplifier 302, 304 which also receives a reference signal on line 313. The output from the differential amplifier is applied to the line 338, and controls the base/collector voltage of transistor 342 which determines the resetting effect of the control windings of the magnetic amplifier, whereby the magnetic amplifier is regulated to provide an output which may be a constant current, a constant voltage, or which may vary as a function of time to control a programme of operation, in accordance with the type of reference signal applied to the line 313. A frequency selective impedance network 318, 320 is included in the feedback line 126 to damp out fluctuations which might otherwise result from sudden load changes and to avoid instability at certain critical frequencies. The voltage-sensitive and current sensitive feedbacks derived from potentiometers 124 and 112 may be combined to form a composite signal which may be employed to impart either a rising or a drooping characteristic to the regulated power supply. An auxiliary power supply, derived from secondary windings 52, 54, 56 of the power transformer, may be connected to operate in parallel with the main power supply output to impart a drooping characteristic to the regulated supply at low load currents, thereby producing a stable output at all current values when the load has negative impedance. A form of function generator to supply a programming reference signal is described (Figs. 3C, 3D, not shown) and a general starting and control system for the apparatus is also discussed with reference to Figs. 6A and 6B (not shown).