Patent GB-191502897-A (GB)
Title: Improvement in Electric Railway Systems.
Inventor: BRETTELL FREDERICK GILBERT
IPC: B60L13/03
Filed: 1915-02-23
Abstract: 2897. Brettell, F. G., [Leffler, C. W.]. Feb. 23. Systems, electro-magnetic and series.-Relates to electro-magnetic railway systems of the k i n d described in Specification 3108/94, and consists in feeding the track electro-magnets and car armature from a sectioned third rail through automatic rheostats, in arrangements and connexions for automatically and progressively changing the magnetic condition of the armature poles, in means for controlling the speed of the cars, and in a device for moving the rotary polechanger should it and the car armature come to rest in a dead-centre position. The track electro-magnets, Fig. 26, are secured to a bar b, mounted on the sleepers and formed with two cement or porcelain troughs b<4>, which carry the main feeders c<1>, c<2>. A porcelain or cement casing b<5> protects the electro-magnets, which are formed with a flanged soft-iron cap b<6> secured to the pole-piece. The system is supplied with a low-voltagecurrent of constant strength through the mains c<1>, c<2>, Fig. 13. The third rail a<3> is insulated and sectioned at intervals of six electro-magnets. the electro-magnets being placed centrally of the track rails, which are sectioned at about one-mile intervals, at which points are towers carrying the automatic rheostats in the feeder c<1>. Adjacent electro-magnets are wound for opposite polarity by means of two windings b<2>, b<3> connected between the supply c<1> and third rail a<3> in two sets of groups of twelve, the two sets being displaced six magnets as regards each other, whereby, when the leading collector e<2> of a car arrives at any particular section of rail a<3>, the six electro-magnets corresponding to that section are fully energized, and the six ahead and behind only partly. The cars carry three collectors, of which the leading and central ones only are in contact at one time and are adapted to connect the sections a<3> to the running rails a<2>, thus energizing the corresponding electro-magnets and the solenoid d of the section rheostat. Owing to the solenoid d being normally dead, the resistance c<5> is cut out from the feeder c<1> until the solenoid is energized by a car on its section. The solenoids are wound with a number of coils having different cross-sections, whereby, as the resistance c<5> is inserted in the feeder c<1> and the current shunted through the electro-magnets, car armature, and solenoid d, the cross-section is gradually increased by the contact member d<3> to the maximum, which is sufficient to take the whole supply current. The car armature, shown in transverse section in Fig. 27 and side elevation in Figs. 15 and 16, is built up from laminated soft-iron sections connected by universal joints f<2>, each section having 24 depending pole-pieces f<1> between which are arranged the windings f<3>, f<4> adapted to produce alternately six poles of opposite polarity, as indicated. The cables to and from the armature lead to a hand-controlled multiplex switch, Fig. 16, each half of which comprises 12 sets of 13 fixed contacts k and four movable blades k<1>. The two halves are identical, and are for different directions of running. The switch is connected by conductors g to a stationary commutator r, the brushes of which are rotated by the pole-changer p driven by the action between its poles and the track electromagnets. The multiplex switch k distributes the current to the armature so that one half passes through one half of the armature windings in one direction, and the other half through the other windings in the reverse direction, thus always producing alternating sets of opposite polarity. The commutator r, being rotated at a speed depending upon the speed of the car, progressively changes the polarity of the armature poles, whereby the interaction of the poles of the track magnets and armature results in a uniform propelling action on the car. The movable blades k<1> are all adapted to move together, and in addition to the central position shown in broken lines, Fig. 16, when the car armature is out of circuit, are capable of taking up four positions on each side of the central one. These positions correspond to multiple, multiple-series (two arrangements), and series groupings of the armature windings for starting and control purposes. By moving the blades k<1> over to the reverse half, a graduated braking action can be obtained. To avoid the possibility of being unable to start the car owing to the poles of the armature having stopped in a dead-centre position as regards the track magnets, an offcentring device is provided, which comprises a soft-iron rod t having projections t<1> and windings t<2> connected with the windings p<2> of the pole-changer and to the segments t<5> of a stationary commutator, the brushes of which are rotated by the pole-changer. A battery Z is carried on the car which is sufficiently strong, when connected up through the hand switch Z<5>, to cause the off-centring device to rotate the pole-changer and thus change, through the commutator r, the polarity of the armature until the correct relation to the track magnets for propulsion is obtained. The two commutators. the pole-changer, and the slip-rings for the various connexions are all mounted together on the same shaft in a common casing. The pair of fixed contacts w, Fig. 16, of the multiplex switch enable the track electro-magnets to be kept in circuit when the car armature is deenergized.