GB855639A - Device for controlling a transductor or other electric amplifier - Google Patents

Abstract

855,639. Magnetic amplifiers. ALLMANNA SVENSKA ELEKTRISKA A.B. April 17, 1959 [April 18, 1958], No. 13120/59. Class 40 (9). The response time of a magnetic amplifier is reduced by passing a large current through the control winding during the transitional period when the current is increasing. The amplifier 1, Fig. 1, may be of the auto-self-excited parallel type, Fig. 2 (not shown), and has its control winding 5 connected in a closed circuit which comprises a variable D.C. control voltage and a D.C. auxiliary voltage of substantially higher value, these voltages being provided respectively by A.C. sources 13, 17 in association with rectifiers 12, 16. Both the D.C. voltages act in the same direction in the closed circuit, and during transient conditions set up a large circulating current which is maintained constant by a high resistance 15. The points 18, 19 on the closed circuit are connected by a resistor 20 and a rectifier 21, a D.C. voltage being developed across the resistor by current through a rectifier 2 and the amplifier output power windings. Under steady operating conditions, the auxiliary voltage supplies current to both the control winding and resistor 20. If the control voltage is raised, however, by adjustment of potentiometer 14, this voltage cuts off rectifier 21 and the whole of the constant current supplied from the auxiliary voltage passes through the control winding. A rapid increase in current through the output power winding then takes place until the voltage across resistor 20 builds up to such a value as to cause the rectifier 21 to conduct. The constant current then passes through both the control winding and resistor 20 once more and a state of equilibrium is reached. The effect of current flow through the control winding when the control voltage is zero may be neutralized by a counteracting winding 22, Fig. 3, energized by the auxiliary voltage. This arrangement also includes the features of output alternating current applied directly to the resistor 20, the provision of a full-wave rectifier between points 18 and 19, a tuned circuit 27 connected to resistor 20 to eliminate the third harmonic and smoothing capacitors 24, 25, 30 across rectifiers 12, 16, 26. Harmonic voltages induced in the control winding are suppressed by a rectifier 31. An amplifier is also described, Fig. 4, in which a further control winding 32 connected in series with the resistor 20 provides rapid transient response when the control voltage is reduced.