GB472394A - Improvements in and relating to electric control systems for regenerative braking of direct current motors - Google Patents

Abstract

472,394. Control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., LIDDIARD, H. W. C., and PETCH, jun., T. H. March 10, 1936, No. 7254. [Class 38 (iii)] Varying E.M.F.-The generator in a Ward- Leonard system has a single field winding only, and the exciter, or the exciter exciting the generator exciter, is driven by independent means having, for example a fly-wheel controlling its drop in speed, means being provided for cutting off the supply to the driving means while the motor excitation is maintained or allowed to decay at a controlled rate. To bring the driving motor to rest quickly in case of emergency a switch 11 is opened to deenergize a relay coil 12 which opens contacts 13 and disconnects a motor 7 driving an exciter 4 which supplies through a controller 5, the field 3 of the generator supplying the driving motor. The shaft of the motor 7 carries a fly-wheel 8 which, acting alone or in conjunction with a friction brake, an oil damper or rotating air vanes, determines the rate at which the speed of the exciter falls. The field 1 of the driving motor may be maintained supplied from an exciter 2 until the field 9 of the exciter is disconnected by a switch 14 acting after a predetermined time interval or in accordance with the falling voltages resulting from the slowing down of the exciter 4. Thus the motor is braked at a rate and to an extent determined by the fly-wheel 8. Instead of maintaining the field 1 of the motor fully excited, the field 9 of the exciter 2 may be disconnected, a condenser or auxiliary flywheel machine being associated with this field as described in Specification 470,771. A brake coil 16 connected across the exciter 4 may trip main brakes at a predetermined voltage across the exciter. In a modification, Fig. 2 (not shown), the exciter driven by the motor 7 supplies, through the controller 5, the field of an additional exciter supplying the generator field. Specifications 267,289, [Class 38 (iii)], and 434,668 are referred to. Reference has been directed by the Comptroller to Specification 267,289.