Patent GB-418436-A (GB)
Title: Improvements in or relating to electrical conversion or transformation systems
IPC: H02M3/40
Filed: 1933-03-20
Abstract: 418,436. Commutator switching arrangements; dynamo-electric machines. PLATEN, B. C. VON, 99, Ostermalmsgatan, Stockholm. March 20, 1933, No. 8379. Convention date, Feb. 22. [A Specification was laid open to inspection under Sect. 91 of the Acts, Sept. 23, 1933.] [Classes 35 and 38 (ii).] In a conversion or transformation system employing static transformers the primary windings of which are fed with mutually phase displaced alternating voltages and in which commutators are connected to the primary and/or secondary windings, at least one alternating current generator having main field poles and intervening auxiliary poles is provided to cover losses in the internal circuits of the system. As shown applied to a system for transforming continuous current at one voltage to continuous current at another voltage, Fig. 1, transformers 5, 6 have primary windings 1, 3 connected through commutators 26, 27 to continuous current mains 36, 37 and secondary windings 2, 4 connected to continuous current mains 24, 25 through commutators 21, 14. The commutator connections are the same as that described in Specification 389,824. The magnetizing current of the transformers is supplied by a two-phase alternating current generator 7 which feeds either the primary or secondary windings or separate tertiary windings 10, 11. The excitation generator 7, Figs. 1 and 8, has main poles 73 designed and energized by a winding 38 fed from a separate continuous current source 39, 40 to produce a voltage wave form of trapezoidal shape with definite zero voltage intervals. In addition the main poles have an opposing winding 48 carrying the primary continuous current and a winding 55 fed through a relay 54 such for example as that described in Specification 388,061 and a rectifier 53 from the winding 52 of a differential transformer 50. The windings 49, 51 of the differential transformer are in series respectively with the primary and secondary windings 1, 2 of the main transformer 5 and normally produce no flux in the core. With incorrect voltage of the generator 7, current is induced in the winding 54 which is rectified, amplified and supplied to the winding 55. The generator has also auxiliary poles 74 which serve to absorb stray flux and also carry windings 41, 47, 59. The winding 41 disposed in slots in the pole faces is fed in series with the main exciting winding 38 to compensate the distortion of the wave form caused by the current in the armature windings 8, 9. The axis of this winding coincides with that of the main poles. The winding 47 carries the load current and is designed so that the machine may supply the entire excitation of the transformers when under load. For small installations the winding 47 may be omitted and the number of turns of the transformer windings 49, 51 adjusted. The third winding 59 on the auxiliary poles is fed through a relay 60, an interrupter 65 and if necessary a transformer 62 from a divided main brush 18, 61 on the secondary commutator 14 so that on the occurrence of sparking due to incorrect commutation, a correcting current passes through the winding. Damping devices for example copper plates 79 are provided on the faces of the auxiliary poles for suppressing higher harmonics. A commutation generator 42, Figs. 1 and 7, having two phase windings 43, 44 in series with the primary windings of the transformers 5, 6 is arranged to induce auxiliary voltages of short duration in the primary circuits during the intervals in which the commutators 26, 27 short-circuit their respective windings. For this purpose the main poles 66 have windings 45 in the primary continuous current circuit. A second winding 56 on the main poles is fed through a relay 57 from the divided brush 34, 58 of the commutator 27 whereby on incorrect commutation an amplified continuous current of appropriate direction flows through the winding. The controlling means for the windings 55, 56, 59 may be interchanged. The main poles may be shaped to give a uniform air gap or one increasing towards the pole-tips. The auxiliary poles 69 are connected with the iron core 70 by a pair of tongues 67 and bolts 71 and serve to hold the main windings 45, 56. Nonmagnetic wedges 72 may be inserted between the main and auxiliary poles. For compensating the magnetmotive force of the armature currents, windings 46 in series with the load are provided in poleface slots. Copper damping plates 80 may be provided on the auxiliary and main pole faces and the wedges 72 may be interconnected at both ends to form a damping circuit. The Specification as open to inspection under Sect. 91 comprises also the following matter. Fig. 10 (Cancelled) shows a six phase synchronous motor or generator having main poles with windings Q1, Q2 and auxiliary poles with windings S1, S2. The stator phase windings P1-P6 are connected to commutators K1-K6 having relatively angularly displaced segments. The commutators are connected in series in a continuous current circuit 105, 106 which also includes the main and auxiliary field windings Q1, S1. The other field windings Q2, S2 are fed from separate sources 101, 102 and 103, 104. An eight phase machine is also described. Specification 323,498, [Class 35], is referred to. This subject-matter does not appear in the Specification as accepted.