Patent GB-437366-A (GB)
Title: Improvements in electrical direct current systems
IPC: H02K57/00
Filed: 1934-02-20
Abstract: 437,366. Synchronous alternating- current machines. PLATEN, B. C. VON, 99, Ostermalmsgatan, Stockholm. Feb. 20, 1934, No. 5587. Convention date, Feb. 22, 1933. [Class 35] Commutating poles and windings; coils; field magnets, dampers on poles of.-A continuous current system comprises a synchronous machine which delivers or is supplied with active current and has main and auxiliary field poles, auxiliary exciting windings on the auxiliary poles and, if desired, on the main poles, a number of transformers, a number of commutators for conversion of the working alternating current into continuous current or viceversa and auxiliary devices connected with the primary or secondary side of the transformers for producing a continuous current proportional to the load for feeding the auxiliary windings. In Fig. 1 the machine G1 is provided with six phase windings P1-P6 supplying continuouscurrent mains 5, 6 through rectifying commutators K11-K16. The main poles are excited by continuous current exciting windings Q2 and compensating windings and commutating windings Q1, S1 are provided on the main and auxiliary poles. These windings are supplied with current proportional to the load through auxiliary commutators K21-K26. If no voltage transformation is required between the mains 5, 6 and the machine, the transformers T1-T6 may be employed simply to feed the windings Q1, S1. An additional winding S2 may be provided on the auxiliary poles to correct for faulty commutation and is supplied from an auxiliary brush e17 and a relay R as described in Specification 388,061. In order to avoid the passage of the transformer magnetizing current through the main commutators, a separate generator G4, Fig. 2, may be provided to supply the excitation. As shown, the phase windings P41-P44 of the exciter are connected in parallel with the secondary windings of the transformers but they may feed the primary windings or additional tertiary windings. The exciter is provided with main and auxiliary shielding poles as described in Specification 418,436. The main poles carry an exciting winding Q42, a winding Q43 fed from a differential transformer T7 through a rectifier 163 and relay R2, and a counter compound winding Q41. The auxiliary poles carry a compensating winding S42 and a series commutating winding S41. The differential transformer functions to correct the voltage of the exciter when the currents in the primary and secondary windings of the main transformers depart from equality. In a modification, Fig. 3 (not shown), the exciter does not supply the magnetizing currents but is designed to relieve the main commutators of reactive currents and accordingly the phase windings of the exciter are connected across the brushes so as to byepass such currents. Consequently a smaller exciter can be employed. A suitable exciter for this purpose is shown in Fig. 4. The rotor comprises main poles 161 carrying the windings Q61-Q63 corresponding to the windings Q41-Q43 of Fig. 2 except that the winding Q61 assists the winding Q62, and auxiliary poles H61 comprising plates the magnetic circuit of which is completed by bolts 170 having distance sleeves 171. The auxiliary poles which also serve to secure the windings Q61-Q63 have pole-face compensating windings S61, the magnetic axes of which are coincident with the axes of the main poles. The rotor is encircled by a copper damping sheath 174. In order to avoid friction losses arising from the use of a number of auxiliary commutators and brushes, the primary windings of the transformers and the phase windings of the main machine may be divided into two parts to give currents of opposite phase, and these windings maybe mesh connected to a single multi-segment commutator having a single set of rotary brushes. An exciter having the same number of phases as the main machine is employed to supply excitation current for the transformers by one of the methods described above.