Patent GB-103959-A (GB)
Title: Improvements in and relating to Regenerative Braking Systems for Electrically Driven Vehicles.
Inventor: TURNER WALTER VICTOR
IPC: B60L7/12
Filed: 1916-08-31
Abstract: 103,959. Turner, W. V., and Thomas, T. H. Feb. 5, 1916, [Convention date]. Systems for continuous-current motors only; electric braking.-In regenerative braking systems the voltage of the motors acting as braking-generators is maintained above that of the line, until a certain minimum speed is reached, by changing progressively the connexions of the motors from parallel to series as the speed of the vehicle decreases, the change being effected automatically by a speed-responsive device, such as a centrifugal governor. A booster generator may be connected in series with the generating-machines for maintaining a substantially constant current as the speed diminishcs. The Figure shows a fourmotor equipment comprising field-magnet oils 15 - - 18 and armatures 2 - - 5, the latter being connected through the brake switch 1 to a " seriesparalleling" switch 14; the switches, etc., for motoring are not shown. The switch 14 is operated indirectly by means of a centrifugal governor 27 driven from a vehicle axle, the governor lever 28 serving to open and close valves 29, 30 controlling the supply of fluid to pistons 31, 32 of a two-part cylinder 33. The piston 31 is connected to actuate the switch 14 against the action of a spring 35. Above a certain speed, fluid is admitted to both pistons, and the switch is held in the parallel position shown; as the speed drops, the piston 31 is first exhausted, and the switch 14 is moved to the "series-parallel" position with the piston 31 engaging the piston 32. A further drop in speed causes the opening of valve 30 and the connexion of the piston 32 to the exhaust, the switch 14 being moved into the "series" position by the spring 35. The armature of a booster 36 is arranged in series with the motor armatures 2 - - 5, the booster field being energized by current from the line 40 through a wire 38, and being controlled by a carbon resistance 41 governed by a solenoid 42 in the regenerative circuit wire 39. The speed of the motor 37 driving the booster is also varied by means of a carbon resistance 43 in its shunt field circuit, the pressure lever 44 being operated by the centrifugal governor and being controlled by oppositely-acting springs 45, 46. Other springs 47, 48 are arranged to act upon the lever 44, but are held out of operation by means of pistons 49, 50 when the switch 14 is in the "full parallel" position. The supply of fluid to the pistons 49, 50 is controlled by the valves 29, 30, so that when these valves are operated by the governor to exhaust the fluid from the pistons 31, 32, the fluid is also exhausted from the pistons 49, 50, and the force of the springs 47, 48 is thrown in succession on the lever 44. The coil of a magnet valve 51 is inserted in the return wire 39, so that when the regenerated current drops to a certain minimum, the valve is opened to vent air from a pipe of the air-brake system and apply the brakes. Another vent valve 52 is actuated by the governor 27 through a lever 53 (adjusted by a hand-lever 55) to vent air from the brake system when the maximum permissible speed of the vehicle is exceeded. Communication from a pipe 56 of the air-brake system to the valves 51, 52 is controlled by a valve 57, which is opened to establish communication at the same time as the switch 1 is moved to the braking position. A switch 58 inserted in the return circuit 13 of the motors is held closed by a piston 59, and air admitted through the valve 57; when the valve 51 opens, the air pressure is released from the piston 59, and a spring 60 opens the circuit 13. The maximum-speed valve 52 is perferably arranged so as to the pressure for causing application of the brakes, but not to release the pressure from the piston 59.