Patent GB-656670-A (GB)
Title: Improvements in constant current electric traction systems
IPC: B60M3/00
Filed: 1948-08-31
Abstract: 656,670. Electric railway systems. PESTARINI, G. M. Aug. 31, 1948, No. 22929. Convention date, March 17, 1941. [Class 104 (iii)] In an electric traction system for supplying power to trains at constant current intensity, and including line conductors subdivided into sections which are connected in series with one another, each line section is provided with a switch which is maintained open when a train occupies that section and is closed otherwise, and a shunt voltage relay connected across the two conductors of each section is adapted to trip and close the associated switch when the line voltage exceeds the maximum value of the back E.M.F. of the motor by a predetermined extent. The control devices may be fully automatic, or dependent on the co-operation between operators at consecutive interconnected stations. Fig. 2 shows a fully automatic system comprising a number of sections, such as 2, 3, 4, each of a length not exceeding the minimum distance between two consecutive trains, and each provided with a short-circuiting switch across the conductors, the switches 7 and 8 of sections 2 and 3 being shown. When a vehicle is on a section, e.g. section 3, the shortcircuiting switch 8 associated with it is held open by a relay 11 connected in an auxiliary circuit with contacts 17 controlled by a coil 14 located in the line circuit towards the forward end of the section and carrying the vehicle current. In the event of a break in the motor circuit of a vehicle on section 3 the voltage build-up across relay coil 24 causes contacts 18 to open and break the circuit of coil 11, thereby closing switch 8 to short-circuit section 3. Since the switch 8 is already closed when a vehicle enters section 3 the current is divided temporarily between the vehicle motors and the path through switch 8. The opening of the switch is, therefore, accelerated by providing, adjacent to the line, auxiliary conductors 15 which are short-circuited by the vehicle and close the circuit of coil 11 to open switch 8, which is subsequently held open by the total current through coil 14. Due to the switch 8 being closed when a train is leaving section 3 the train motors are short-circuited and, as a safety measure, the motor field windings are either disconnected or short-circuited by a relay which becomes energized when a shoe carried by the train runs upon an earthed conductor 22 adjacent to the end of section 3. By providing an effect equivalent to the action of the conductors 15 and vehicle contactor throughout the length of a section to energize coil 11 the relay coil 14 can be dispensed with. This effect is embodied in a modification, Fig. 4, which is adapted for travel in both directions and wherein co-ordinated manual control is provided at stations 203, 304 interposed respectively between sections 2, 3 and 3, 4. At these stations two short line conductors insulated from the corresponding conductors of the adjacent sections are adapted to be connected alternatively thereto by circuits each including a pair of circuit breakers, such as the pair 25 and 26 at station 203. These circuit breakers are actuated by coils 27, 28, respectively, in circuits controlled by a rotary controller 33 with operative positions S and D and control " off " position O, there being a similar controller 34 at station 304. To bring a vehicle from station 203 to 304 the controller 33 is swung to position D and controller 34 to position S and, since relay coils 28 and 11 are not then energized, the contacts 39 and 35 are already closed, so that a circuit is made from an auxiliary D.C. supply, over sector 55 to energize the coil 27 and close circuit-breakers 25. The line conductors of station 203 are thereby connected to the lines of section 3. By operation of controller 34 to position S the sectors 57, 58 close an auxiliary circuit back to the sector 56 of controller 33 and over closed contacts 42, 63, 65 to energize relay coil 11, these connections being allowed by relays 27 and 32 being energized and voltage coil 24 de-energized. Relay coil 11 then opens the short-circuiting switch 8 across the lines of section 3 and current is fed through the vehicle on the section. Meantime relay 11 has opened the contacts 35 in the lead to relay 27 which is now fed over holding-contacts 36. The controller 33 at station 203 may now be released to " off " position, but controller 34 at station 304 is' maintained at position S until the vehicle arrives at that station. The Specification as open to inspection under Sect. 91 describes also the provision of a pushbutton at each of stations such as 203, 304, these buttons being connected in an auxiliary circuit arranged to energize coils such as 10 and 11 after an emergency stopping has been effected by shifting the manual control lever to the central or " off position. This subjectmatter does not appear in the Specification as accepted.