GB121753A - Improvements in and relating to Electric Motor Control Systems. - Google Patents

Abstract

121,753. British Thomson Houston Co., (General Electric Co.). July 31, 1917. Systems for continuous-current motors only.- In regenerative braking systems for series motors in which the field-magnet winding of the machine is supplied during the braking operation with current from an exciter, this exciting current is so regulated that the speed-current braking characteristic is sufficiently like the normal seriesmotor-characteristic that the change of connexions may be made at any speed without an excessive change in torque. In one arrangement, Fig. 1, power is supplied from a trolly 14 to a pair of traction motors having armatures 10, 12 and series field windings 11, 13; these motors are connected in series and in parallel by means of a main controller C associated with a starting resistance 17. A motor-generator set 20 is used for regenerative braking, the motor 21 of this set being supplied from the trolly 14 through a starting resistance 22. The generator or exciter E is provided with two armature windings and commutators 23, 24 which are adapted to be connected across the field-magnet windings 11, 13 by means of a braking controller B. The exciter E is provided with a field-magnet winding 26 energized by a self-excited generator 29 and with a winding 25 carrying the full current of the traction motors; during the regenerative braking operation, the winding 25 acts in opposition to the winding 26 so as to give the exciter E a drooping or constant-current characteristic. The voltage of the exciter is adjusted by means of resistances 32 in circuit with the winding 26. In modifications, the winding 26 may be self-excited, and the winding 25 may be dispensed with, the drooping characteristic of the exciter being effected by designing the machine with a high armature reaction. During regeneration, the sum of the currents in the armature and field magnet windings of the traction motors are maintained substantially constant. In another arrangement, the exciter armatures are connected in series with the motor field-magnet windings, and variable resistances are connected in shunt across the two (motor field-magnet winding and exciter armature). Specification 22868/07 is referred to.