GB864714A - Improvements in electric remote control devices - Google Patents

Abstract

864,714. Magnetic amplifiers. BROOKE, W., and HOWE, H. May 11, 1959, No. 16023/59. Class 40 (9). A controlled saturable reactor in the circuit between an A.C. motor M, Fig. 1, and singlephase lines L1, L2 comprises two cores A, B, provided with respective main windings PA1, PA2, and PB1, PB2, control windings NA1, NA2 and NB1, NB2, and optional separate feed-back windings SA1, SA2 and SB1, SB2, the main windings being connected in seriesparallel with a rectifier T1 linking the midpoints W1, W2 of the parallel circuit, and arranged so that windings PA1, PA2 are in different parallel branches and act in one sense in relation to the control windings on core A, while the windings PB1, PB2 also in different branches act in the opposite sense in relation to the control windings on core B. The rectifier T1 completes circuits for second harmonic currents which arise in the main windings each time a core saturates, the harmonic currents providing a positive feed-back action by circulating in the two closed paths comprising windings PA1, PB2 and PB1, PA2, and the common rectifier. When the optional separate feed-back windings SA1, SA2, SB1, SB2 are provided, they are connected with a rectifier T2 to form similar closed circuits as the main windings and rectifier T1, the second harmonic currents being generated by induction. The rectifier T1 may then be omitted. A modified arrangement of the feed-back windings is shown in Fig. la which permits the winding pairs SA1, SB1 and SA2, SB2 to be replaced by single windings common to both cores. It is stated that the main winding mid-points W1, W2 may be linked by a resistor or a resistor Rn in series with a reversed rectifier T1E, Fig. 11, to provide negative feedback. The arrangement may be applied to a three-phase system L1, L2, L3, Fig. 9, supplying a star or delta-connected motor, each phase being provided with a similar reactor C1, C2, C3 the control windings of which are connected together in series-parallel, Fig. 10, and energized over rectifiers T6 and a transformer R from the three-phase system. The connection of the control windings, which may include the links shown in broken lines, suppresses induced currents which would otherwise circulate in the windings. A choke N is provided for the same purpose in Fig. 1.