GB725802A - Commutatorless converter fed motor - Google Patents

Abstract

725,802. Converting. BROWN, BOVERI, & CIE AKT.-GES. Jan. 12, 1953 [Jan. 19, 1952], No. 904/53. Class 38 (2). Windings of a motor are fed through valves with grid-controlled anodes arranged in groups of four, each group comprising two pairs such as b, c; d, e; f, g ; h, i, the members of each pair being connected respectively to the ends of the secondary winding of a transformer, centre tapped at a, while the two cathodes associated with the anodes of each pair are connected together, the two joined cathode pairs of each group of four being connected to opposite ends of a reactor centre tapped at k. The tappings a and k are connected to fixed points I, II, III, IV symmetrically disposed around the motor winding. The grids of the valves are impulsed simultaneously at the supply frequency for speed control and at a frequency proportional to the motor speed, and the pairs of valves fire in succession, each for a quarter of a revolution where, as in Fig. 1, there are four pairs of valves. The whole of the motor winding carries current substantially continuously. Commutating voltage may be provided from commutating poles which are continuously excited by parallel windings connected in the leads to the ends of the reactors. Compounding may be effected by similarly connected parallel windings on the main poles. The commutating poles may have damping coils or cages. When the poles rotate to avoid too many slip rings the parallel windings may be the field windings of a separate exciter which supplies the poles of the main motor with proportional D.C. In modifications there may be three or more groups of four valves, Fig. 2 (not shown), the supply may be polyphase, Fig. 3 (not shown), and the motor windings may be connected in star, Fig. 3 (not shown).