Patent GB-302163-A (GB)
Title: Improvements in or relating to voltage regulators
IPC: H02P9/32
Filed: 1928-12-10
Abstract: 302,163. Associated Electrical Industries, Ltd., (formerly Metropolitan-Vickers Electrical Co., Ltd.), (Assignees of West, C. P.). Dec. 9, 1927, [Convention date]. Exciting; regulation of exciting machines.-In regulating the voltage of electric generators according to one or more characteristics of the generator such as voltage, current or powerfactor, the field of the generator or of an exciter is supplied from an alternating current source through a rectifier &c. and the effective reactance of a reactor in the alternating-current circuit in series or parallel with the rectifier is controlled by additional windings excited according to the characteristics and so controls the field current. In a direct-current generator 1, Fig. 1, the field 11 is supplied from an alternating-current source 7 through an adjustable reactance 8, windings 6 of a reactor 5 and copper-oxide rectifiers 10. The reactance of the windings 6 is controlled by opposed windings 12, 14 respectively in the field circuit and across the mains 3, 4. The field of the windings 6 is confined to the outer limbs of the core. When the generator 1 is at rest, the coils 6 are of high reactance and a small current is supplied to the field 11. As the generator voltage builds up on starting, the winding 12 preponderates over the winding 14 and the unidirectional flux in the centre limb of the reactor core 5 is increased to reduce the reactance of the coils 6 and so to increase the current through the field 11. The field and voltage of the generator 1 are similarly controlled subsequently. An additional winding 15 energized according to the current in the bus 4 provides over- and under-compounding according as the winding 15 aids or opposes the winding 12. In a modification, the reactor windings 6 are on the upper and lower limbs of the core and are in parallel to the rectifier 10 and an additional coil on the centre limb between the coils 12, 14 and opposing the coil 12 is supplied from the source 7 through an additional rectifier in order to magnetize the core and reduce the impedance of the reactor, and so to reduce the field current, when the generator is stationary. In an alternating-current generator, the source 7 may be replaced by a shunt across two phases and the coils 14, 15 are supplied through rectifiers from a shunt circuit and from a current transformer. In a modified circuit for alternating- current generators, the field 33, Fig. 3, of an exciter 34 for the generator 1 is supplied through a rectifier 31 from a constant-current transformer 30 supplied from a separate source or from the mains 17 and the controlling reactor windings 35 are in parallel to the rectifier 31. Coils 38 - - 40 on the reactor core are energized according to the current in the main 17, the field current of the generator 1 and the voltage of the mains respectively and an additional winding 41 to magnetize the core is supplied from a rectifier 32. The winding 39 hastens the regulating action. No current flows in the coil 40 when the voltage is normal, the coil being connected as shown to the junctions of equal resistances 48, 49 and rectifiers 44, 45 supplied from transformers 46, 47 in parallel circuits including an inductance 50 and resistance 51. Change of voltage in the mains disturbs the balance and supplies current to the winding 40 in one direction or the other according as the voltage is high or low. The exciter may be omitted, the field of the generator 1 being supplied from the rectifier 31. In a further modification, Fig. 5, the field of the generator 1<1> is supplied from the mains 17 through transformers 76, controlling reactances 77 and mercury-arc rectifiers 75. Each reactance 77 has a winding 81 energized according to the main current, a winding 82 energized according to the main voltage by a balance method similar to that used in Fig. 3, a magnetizing winding 83 supplied through a rectifier 95, and opposed windings 84, 85 whose energization depends on the power-factor. Rectifiers 96, 97 supplying the windings 84, 85 are supplied from current transformers 100, 101 and from a voltage transformer 94, respectively through a capacity 98 and inductance 99 so that the windings 84, 85 are energized in accordance with the resultant of the load current and a current in loading or lagging quadrature to the load voltage. At unity powerfactor, the effects of the windings 84, 85 balance the field of the generator or of its exciter, being increased and decreased for lagging and loading power-factors respectively.