GB417502A - Improvements in and relating to control systems for the motors of electrically driven vehicles employing regeneration for braking purposes - Google Patents

Abstract

417,502. Master control of D.C. motors; controllers. WILLIS, A. M., 59, Victoria Street, Bristol. Dec. 29, 1932, No. 36798. [Class 38 (iii).] Regenerative braking.-A compound-wound vehicle motor is controlled during motoring and regeneration by power and brake controllers respectively, the brake controller being adapted to regulate the shunt field, and to modify the series field so that the series and shunt excitations do not oppose, and the connection of the armature to the supply being made automatically upon operation of the brake controller, only when conditions are suitable for regeneration. A controller 5 is operated by a pedal 9 in an anti-clockwise direction to connect the compound-wound motor 13 to the supply, and accelerate it by first cutting out series resistance 29 in steps, and then inserting resistance 33 in steps in the shunt field 2, the line contactors being maintained by a switch 10 frictionally operated from the controller shaft so that return movement of the controller disconnects the motors, and allows the vehicle to coast. With the motor disconnected, and its speed such that a centrifugal switch 90 is closed, and the back E.M.F. is in excess of the line voltage, so that a differential relay 95 is closed, operation of the controller 5 in a clockwise direction by means of a pedal 8, causes contactors 27, 103 to close and connect the armature to the supply, the vehicle being regeneratively braked, and slowed down by further clockwise operation of the controller 5 to cut out, in steps, resistance 109 now included in the shunt field circuit which also includes the series starting resistance 29, and the series field 1, final clockwise movement of the controller releases the air brakes, the relay 95 is provided with an anti-hunting coil. In a modification, two separate electrically interlocked controllers for driving and braking are provided, and when, during regenerative braking, the motor has been connected to the line, the control of the line switches is transferred from the voltage balance relay to a cut-out relay which disconnects the motor when the armature current changes from regenerative to motoring, the voltage balance relay again effecting the automatic connection for regenerative braking if and when the armature voltage is suitable. The cut-out relay may be polarized and one coil of the voltage balance relay may be connected across a motor line switch. Movement of the braking controller may short-circuit the series field. A resistance in the vehicle lighting circuits is automatically switched in on excess voltage.