Patent GB-506681-A (GB)
Title: Improvements relating to voltage-sensitive electrical circuit arrangements, and electrical voltage-controlling systems
IPC: H01H47/20
Filed: 1937-12-14
Abstract: 506,681. Automatic regulators; electromagnetic switches. INVEXCORPORATION. Dec. 14, 1937, No. 34615. Convention date, Dec. 14, 1936. [Class 38 (iv)] [Also in Group XXXVII] The invention relates to a voltage sensitive ferro-resonant circuit having a characteristic with a pronounced hysteresis effect and operating a relay. A series resonant circuit including a saturable inductance operates a relay when, upon rise in applied voltage, a resonant condition is reached and the relay then acts upon an element in the circuit separate from the relay so that the dissonant point (at which the circuit falls out of resonance with falling voltage) is brought near to the resonant point, either by change of effective inductance or of capacitance. The resistance of the circuit is not materially affected. Fig. 1 shows a circuit comprising saturating inductance 6, capacity 7, inductance 8 and temperaturecompensating resistance 9. When the relay 10 operates, on resonance, a resistance Ro shunting the inductance 6 is replaced by a resistance Rr so that the fall of voltage required to release the relay lies inside the tolerable change in circuit voltage. As shown a relay 3 is operated from the relay 10 to control the tapped primary of a transformer 2. Numerous modifications of this arrangement are described which are adapted for interchangeable use with or without the relay 3 or relays affecting other types of voltage adjustment. In addition to modification of resistance in parallel with the inductance 6 which in one form is arranged as an auto-transformer, a resistance in series or in parallel with the relay 10 may be modified by the relay to change the effective inductance in the circuit, or condensers in parallel with condenser 7 may be selectively connected by the relay. The resistances and condensers are adjustable to determine the resonant and dissonant points. Fig. 8 shows the control of the series boosting winding 11b of an auto-transformer wherein the relay 10 controls a relay 14 with contacts 10a, 14a in its maintaining circuit, contact 10b to remove the resistance Ro and energize the relay 14 and contact 14a to energize contactor 12 and insert the resistance Rr. Two control circuits of the kind described may control separate contactors for a two stage boosting winding. Fig. 11 shows the control of line voltage by condensers c<1>, c<2>, c<3>. A latched circuit breaker 17 and its releasing coil 21 are controlled by contacts d on relays R, O respectively (the relays,18, 19 being provided only for removing current from circuit breaker coil 17 after energization). The relays R, 0 are controlled by a time delay relay Sunder the selecting action of a relay M, and the relay S is energized by the relay 10 through interlock contacts on relay M. The resonant and dissonant points are controlled by resistances Ro, Rr in shunt with the inductance. 6 and inductance 8 respectively, and varied by the action of contacts on the relays 10, R and O. A no-volt relay NVR is included. A modification of this system is described in which NVR is omitted and the switch R, 0 replaced by a single relay which is operated through a latching relay controlling the resistances Ro, Rr ; these two relays also replace the relay M. The time delay relay ensures that voltage adjustment shall not take place on transient changes in line voltage.