GB663030A - An improved phase-shifting network - Google Patents

Abstract

663,030. Control of A.C. motors. BRIGGS, G., and BRITISH VACUUM CLEANER & ENGINEERING CO., Ltd. Oct. 28, 1948. [Sept. 29, 1947] No. 21316/50. Class 38(iii) [Also in Group XXXV] The phase of an alternating - current flowing in a first circuit, such as motor armature 31, is shifted relatively to the phase of an alternating - current flowing in a second circuit, for example field winding 29. The first circuit is connected to an A.C. source without the interposition of variable phase-shifting means and the second circuit is supplied with alternating-current from the secondary winding 28 of a transformer 24 having two oppositelywound primary windings 23, 25. The winding 25 is connected to an A.C. source 22 through a condenser 26 to advance the phase of the current flowing therein. The primary winding 23 is connected in the anode circuit of a thyration type valve 19 the anode of which is supplied with alternating-current, means being provided for varying the potential applied to the grid of skid valve relative to the anode voltage in order to alter the firing-point thereof so as to change the phase of the current flowing in the primary winding 23, thereby varying the phase of the current flowing in the second circuit relative to that of the current flowing in the first circuit. The particular description relates to the motor control system described in Specification 643,036. Fig. 2 (not shown) graphically illustrates the wave-forms of currents in the winding 28 under different conditions of the valve 19.