Patent GB-189761-A (GB)
Title: Improvements in or relating to self-regulating dynamos
IPC: H02K23/02
Filed: 1922-11-03
Abstract: 189,761. Etablissements H. Crochat. Nov. 26, 1921, [Convention date]. Void [Published under Sect. 91 of the Act]. Exciting. - The normally drooping excitation characteristic O, J, K, L, Fig. 3, of a dynamo wholly or in part shuntexcited, is automatically kept approximately to an extension J, M, K<1> of the straight part OJ by providing the machine with additional ampÞre-turns fed from a source external to the machine and arranged to excite it at and from the point J where the curve begins to bend. In the form shown in Fig. 4, the shunt machine 1 under regulation, which supplies the load 4 in parallel with a buffer battery 3, receives additional excitation from a coil 5 when its volts reach the value v<x>. Fig. 3. The coil 5 is supplied by opposing armatures 7, 9 driven by a motor 6 and excited with a common current from the shuntwound machine 7 which, by means of a field regulator 8, produces a constant a voltage. The motor 6 is driven by the battery volts and when these rise beyond a certain value the increased speed of the motor causes the armature 9 to generate a voltage in excess of that of the armature 7 and so excite the coil 5, raising the point K to K<1>, Fig. 3. The generator 1 thus gives a voltage v<kl> at the same speed as that at which it gives the value v<x>. In the arrangement shown in Fig. 5, a supplementary armature 7 is keyed on the shaft of the main generator 1 and the additional exciting coil 5 is fed by the difference of the voltages of the two armatures, which voltages are normally equal at the point J, Fig. 3, on the curve. The machine 7 has a shunt regulator operated by a coil 8<2> shunted across its brushes. As soon as the regulator limits the volts of the armature 7, corresponding to the point J, the coil 5 receives the excess volts of the machine 1 over those of the armature 7, and so provides the additional ampÞre-turns to raise the curve to the values on the line J, M, K<1>, Fig. 3. A compounding coil 8<3> on the regulator, connected across the battery, may be used to give the coil 5 additional current. In place of regulating the volts of the armature 7 by altering the field in which it turns, they may be regulated by altering the magnetic resistance of the magnet. The constant counter-electromotive-force armature 7, Fig. 5, may also be replaced by a battery 11, Fig. 6, of sufficient size to give practically constant volts. Also an automatic cut-out 10 may be used to open the circuit of the coil 5 when the volts of the auxiliary armature 7 drop below the value v<x>, Fig. 3. The supplementary excitation given by the coil 5 may alternatively be given by some of the shunt coils which carry a current apart from the normal shunt current. The invention is stated to be applicable chiefly " for motors, the power of which decreases fairly quickly owing to an increase in the most favourable angular speed which is the case for nearly all the motors whether they be thermic electric (shunt, series, asychronous) o : others," and synchronous motors. It is particularly applicable to vehicle and like installations comprising a motor, dynamo and battery.