Patent GB-389824-A (GB)
Title: Method of and means for controlling converter plants
IPC: H02M3/40
Filed: 1931-09-17
Abstract: 389,824. Converting ; rotary converters and transformers. PLATEN, B. C. VON, 99, Ostermalmsgatan, Stockholm. Sept. 17, 1931, No. 26056. [Classes 35 and 38 (ii).] Exciting.-In a system for converting D.C. to D.C. or D.C. to A.C. having a transformer in an intermediate stage, the magnetizing current for the transformer is supplied from an external source to a third winding ,and is automatically adjusted to maintain the ratio between the input and output currents constant. This maintains at all loads a fixed phase relationship between the primary and secondary currents and thus ensures efficient commutation with a fixed setting of the commutating devices. In the form shown in Fig. 1 D.C. from a source 20, 21 is converte'd'to A.C. by a commutator switch, 4 and supplied' to'the primary of a transformer 19, the output from the secondary 3 of which is rectified by a commutator switch 5. The transformer 19 has a third winding 6 which is supplied from a small A.C. generator 24 mounted on the same shaft as the switches 4, 5, which has two auxiliary fields 28, 29 connected respectively in the D.C. input and output, and so proportioned that their fluxes cancel when the currents in the input and output circuits are in the right ratio. When out of balance occurs one or the other predominates and causes either an increase or a diminution of the main field and therefore an adjustment of the supply to the winding 6 to' correct for the out of balance. Small generators 25, 26 are connected in the primary and secondary circuits of the transformer 19 to aid commutation at the switches 4, 5. In a modification the system is doubled, the second transformer working 90" out of phase with the first, and the outputs combined. In a modification shown in Fig. 3 the excitation of the small generator 24 is adjusted by means of an auxiliary transformer 54 having opposing windings 52, 53 connected respectively in the primary and secondary circuits of the transformer 19, and a third winding 55 which is connected through a rectifier 56 to a relay 63. The windings 52, 53 are proportioned so that when the currents in the primary and secondary circuits are in the desired ratio the resultant flux is zero. Any out of balance will cause a flux to flow 'and an e.m.f. will be induced in the coil 55 in phase with the one that predominates. The rectified current operates a relay 63 which connects either coil 66 or coil 67 to a D.C. supply to effect restoration of balance. Instead of having an auxiliary transformer 54, the winding 55 may be mounted on the core of the main transformer 19. Fig.: 4 shows a modification in which adjustment of the ratio of input and output voltages can be obtained. An additional transformer 72 having a tapped secondary is connected, between the commutator switch 4 and the primary of the transformer 19. In series with its primary is an adjustable choke 81. The tapping switch and the adjustable core of the choke are coupled together by a link system so that in adjusting the ratio of transformation alteration of the choke effects an adjustment of the circuit constants to meet the new condition. The invention is applicable to'systems utilizing rotary transformers of the type described in' Specifications 360,418, 369,993, and 388,061.