GB252189A - Improvements in and relating to electric motor control systems - Google Patents

Abstract

252,189. British Thomson-Houston Co., Ltd., (Assignees of Hamilton, Tl%. S. H.). May r6, 1925, [6o?tvention date]. Regenerative systems for traction or other purposes. The driving motors M<1>, M<2>, Fig. 1, in regenerative braking, are excited by separate machines E<1>, E<2> having a common series fieldwinding F<4> and a common shunt field-winding F<3>. The exciter shunt field is automatically varied in strength by 'a rheostat 18, Fig. 3. driven by a reversible motor 19. During the first period of regenerative braking prior to the .exclusion of the starting resistances, the rheostat motor is under the control of a relay 24 responsive to the regenerated voltage, which ia thus maintained at a constant predetermined value. For the second period of regeneration with exclusion of the resist. a.nces a switch 4 is caused to by-pass the relay 24 and put the motor 19 under the, control of a relay 25 responsive to the strength of regenerated current, which is thus definitely limited. A greater strength can be obtained by manipulation of the controller so as to oppose the relay winding 25 by a winding 26 energized from the supply mains, or alternatively a lower limit of strength may be set by connecting the winding 26 so as to assist the winding 25. A selective controller S.C. is arranged to give series or parallel braking at will. The system comprises carn-operated and interlocked contactors for starting and accelerating the motors, and is described in detail in the Specification.