Improvements in and relating to the control of direct-current motors by means of grid-controlled rectifiers

摘要

619,094. Rectifying. BROOKE, W., and BALDWIN, H. T. Nov. 20, 1946, No. 34335. Drawings to Specification. [Class 38 (ii)] [Also in Group XXXVII] A control system wherein a direct-current motor is supplied from alternating-current mains through two groups of grid-controlled rectifier valves, which are each arranged to be rendered respectively conductive or non- conductive so as to energize the motor in opposite directions, is provided with means to produce such a phase-shift of the grid voltages of the valves which are to be made inactive that the possibility of the firing of these valves due to transient currents is avoided. Condensers are introduced into the grid circuits of the inactive valves so as to produce a phaseshift of 180 degrees therein, means being provided to short-circuit these condensers during the active operation of the valves. The shortcircuiting of the condensers may be effected. by a multi-polar switch or a remotely-operated relay.