GB459443A - Improvements in the regulation of rectifiers by means of grids - Google Patents

Abstract

459,443. Rectifying alternating current. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET, Võsteras, Sweden. July 3, 1935, Nos. 18996 and 18997. Convention dates, Nov. 1, 1934 and May 17, 1935. [Class 38 (ii)] A grid-controlled rectifier is automatically regulated to maintain constant voltage, constant current, or constant power output by an arrangement comprising a phase shifting impedance network for the grid potentials, one element of the network comprising a variably saturated inductance in which the saturating current consists of the difference between a standard current and a current proportional to the quantity to be regulated. In the arrangement shown in Fig. 1, the grids of a rectifier 1 are fed from transformers 31 through resistances and inductances 3 associated with saturating windings 30. The latter are fed from points 8, 10 with the difference between a standard current derived through a stabilizing resistance 4, transformer 5, rectifier 6 and smoothing circuit 7, 11, and a current proportional to the output voltage of the rectifier 1. A compound voltage characteristic may be imparted to the rectifier by causing the standard current to vary with load by energizing a winding 50 on the transformer 5 from a current transformer 12 on the primary side of the main supply transformer. A relay 13 may be arranged to introduce a stand-by stabilizing resistance 40 in the event of failure of the resistance 4. Switches 15, 16 may be associated with the ignition device or main circuit breaker of the rectifier in such manner that the transformer 5 is cut out when the rectifier is inoperative. In a modification, Fig. 2 (not shown), the saturating windings are fed with the difference between a standard current derived as in Fig. 1 and a current proportional to the rectifier load current derived through current transformers and an auxiliary rectifier. Fig. 3 shows a further modification wherein a current proportional to the rectifier load current is supplied through a resistance 70 and inductance 71 to a rectifier 73, and the saturation of the inductance 71 is varied in accordance with the voltage of the main rectifier 1 by a winding 72. Thus a current proportional to the power output of the rectifier 1 is delivered by the rectifier 73 and balanced against a standard current supplied by a rectifier 54, the difference serving to energize a saturating winding 55 controlling the grid phase shifting circuit 60 to effect regulation of the rectifier to constant power. Specification 412,773 is referred to. According to the Specification as open to inspection under Sect. 91, the controlling current may supply one field component of a synchronous machine instead of energizing a saturating winding of an inductance. This subject-matter does not appear in the Specification as accepted.