Patent GB-307046-A (GB)
Title: Improvements in electric regulating and controlling devices
IPC: H02P7/00
Filed: 1928-11-19
Abstract: 307,046. Akt.-Ges. Brown, Boveri, et Cie, (Assignees of Osterreichische Brown, Boveri-Werke Akt.-Ges.). March 3, 1928, [Convention date]. Regulation, automatic; systems depending on two or more machines. -Automatic means adapted for regulating from a distance an electrical factor or a factor which, for regulating purposes, is represented by such, comprises a differential relay upon which the said factor and an adjustable factor of comparison co-operate to effect direct or indirect adjustment of the regulating members. Means for preventing over regulation are included. Arrangements are described for controlling the voltage of a generator and the frequency of supply mains. A reversible motor 16, Fig. 1, controlling the excitation of a generator 13 is controlled by a differential relay the coil 8b of which carries an adjustable current determining the voltage of the generator.. To prevent overregulation a coil 8c is connected to a potentiometer 18 through an arm 20 which is moved by coils 22 according to the operation of the regulator. Stops 23 and a retarding device (not shown) are used to adjust the operation of the arm 20 so that all hunting is checked. The modification shown in Fig. 2 has a potentiometer 18, in series with the circuit of the coil 8b, and governed by a reversible motor 24. The motors 16, 24 are respectively controlled by pairs of contactors 29, 30 operated by the differential relay. Auxiliary contacts governed by the motor 24, auxiliary contacts on the contactors 29 and adjustable stops 33 control the anti-hunting effect of the potentiometer 18. Where the factor to be controlled is a frequency the differential relay may have coils 40a, 40b, Fig. 3, which carry equal currents at the desired frequency, whereas the balance is appropriately disturbed upon departure therefrom. A transformer 39 in series with a rectifier 38 and transformers 34, 35 subject to the controlled and controlling frequencies respectively produces in its secondary circuit a frequency equal to twice the beat frequency in the primary circuit and the coils 40a (with series inductance 41) and 40b (with series capacity or resistance 42) are connected to this secondary circuit. To avoid the influence of voltage variations two jointly adjustable frequencies are preferably used as the factor of comparison. Two generators 36, Fig. 4, of different pole numbers are coupled together and feed independent circuits for the coils 40a, 40b each of which is similar to Fig. 3. Thus the coils may balance when the regulated frequency is 50 periods per second if the two generators produce frequencies of 48 and 52 periods per second respectively. Electron tubes or vibrating relays may be used to reinforce the rectified currents'. Over-regulation may be prevented by automatic variation of the field current of a motor 49 driving the generators, the regulating contactors 45 controlling the extent of a potentiometer 51 which energizes the field. In all the arrangements described the controlling factor may be adjusted at a distant point and a meter 10, 28, 36 may indicate the condition of the adjustment. The Specification as open to inspection under Sect. 91 (3) (a) describes also an arrangement controlling the temperature of an electrically heated furnace. Fig. 1 (Cancelled) shows a switch 4 in the supply to a furnace heater 2 which is controlled by a differential current relay the coil 8b of which carries an adjustable comparison current and holds the switch closed until the thermometer 5 reaches a corresponding temperature, at which, by the short-circuiting of a portion or portions of the resistance 6, a balancing current is produced in the coil 8a. This subjectmatter does not appear in the Specification as accepted.