Patent GB-190314172-A (GB)
Title: Improvements in Systems for Electrical Distribution.
Inventor: TALL FREDERICK WILLIAM LE
Filed: 1903-06-25
Granted: 1904-07-25
Abstract: 14,172. Le Tall, F. W., [Cooper-Hewitt Electric Co.]. June 25. Motors, controlling. -Relates to systems of electric distribution in which currents from an alternating or direct current source are rectified when necessary and regulated by rectifiers having a high initial resistance, such as Cooper- Hewitt mercury devices. The rectifiers are provided with adjustable means for starting them at any desired point of a wave or cycle, thereby regulating the amount of energy supplied to the translating devices. The system is applicable to electric railway or elevator circuits. In the arrangement shown in Fig. 1, one terminal of each of the direct-current motors 3, which may be electric railway motors, is connected through one of the oppositely-arranged rectifiers 5 to the main 1 of a single-phase alternating-current source. Each rectifier is provided with an additional terminal 11 or 13, connected to switch arms 9 adapted to be connected to the spaced leads of the secondary coils 7, 8 of a transformer having a primary 6 connected across the mains. The secondary coils 7, 8 are connected respectively to the mains 1, 2. A spark gap 64 may be arranged in one or both secondary circuits. The current, which flows in the same direction through both motors, is broken at each zero point, and is restarted when the potential induced in the secondary coils is sufficiently high to break down the starting-resistance of the rectifiers. The part of the cycle in which this occurs varies according to the length of the secondary coils. Fig. 3 shows another arrangement applied to a three-phase system of which 14, 15, 16 are the mains. A motor for an electric elevator or other translating- device 19 is connected to the mains by wires 17, 18 and rectifiers 31, 32 arranged to pass current in the directions indicated by the arrows ; currents flowing through the motor from the conductor 16 to the conductor 15, from 15 to 14, and from 14 to 16. Each rectifier has an additional terminal 92 to 101, the leads from which are connected to contact-segments on discs 50 to 53 secured on an axle 54 rotatable by the hand-wheel 55 and worm gearing. An arm 45, carrying brushes 46 to 49 to engage these contact-segments, is carried round the discs 50 &c. by a synchronous motor 20 driven from the mains 14 to 16. The brushes 46 to 49 are connected to the contact-rings 40 to 43 secured on the axle 21 of the motor 20 and engaged by brushes connected to exciting generators 29, 30. Each time the current phase changes, the flow through the rectifiers ceases until the generators 29, 30 are connected to the additional terminals 92 &c., and a critical strain is produced by the terminals 91, 92, &c. The part of the cycle at which this occurs is varied by turning the shaft 54 so that all, or only a part of, a cycle may be utilized. The contact-segments of the discs 50, 51 which correspond to rectifiers in one direction are stepped with regard to the segments of the discs 52, 53 which correspond to the other rectifiers. It is necessary, however, that corresponding contacts of all discs should be in engagement simultaneously, as each circuit through the motor 19 includes a rectifier of each direction. Fig. 5 shows an arrangement applied to a two-phase system 111, 112. Translating-devices 117, 118 are connected to the mains by conductors 113, 114, a vapour lamp 133 being included in the circuit. Starting-bands 136, 137 encircling the electrodes are connected through transformer secondary coils 131, 132 to either of the conductors 113, 114. The primary coil 119 is connected in series with a suitable inductance 120 across the mains. The rectifier is controlled by throwing resistance in shunt with the primary. As shown, differentiallywound shunt and series coils 129, 130 arranged in the translating-circuit act on a core 128 connected to a weighted lever 124, which actuates a rod 123 carrying a contact 122 over the contacts of a resistance 121. If the voltage in the receiving-circuit diminishes, a portion of the resistance 131 is cut out, and vice versÔ, the acceleration or retardation of the secondary electromotive forces, and hence the lines of the critical strains on the starting- bands 136, 137, being thus determined. In the arrangement shown in Fig. 6, translating-devices 152, 153 are fed from an alternating-current generator 139 through a rectifier 141 having a starting- band 142 connected tu the main 112. The primary coil 119 is inserted in series with a resistance 143 across the mains. The length of the secondary coil is adjusted so as to vary the point of starting by the contact 145 actuated through the mechanism shown from the core 150 of a coil 151 arranged across the receiving-circuit. The field coils 140 of the generator are connected through a rectifier 200, the starting-band of which is controlled by the coil 144. Fig. 7 shows the invention as applied to a direct-current source 154, 155. The invention depends upon the fact that, when a condenser is suddenly connected across the mains, the current through a rectifier is interrupted until a breaking strain is again applied. Translating- devices 158, 159 are connected to the mains through a rectifier 160, having a starting-band 162 connected through a transformer secondary 163 to the main 155. The primary 164 is connected across the mains through a switch comprising brushes 165, 168 adapted to be connected by a contact 167 on a disc loosely mounted on a shaft 170 driven by a motor 179. A condenser 161 is connected across the mains through brushes 175, 176 adapted to be connected by a contact 174 on a disc 172 mounted free to slide only on a shaft 170. The discs 166, 172 are connected together by inclined teeth and slots 173 formed on or in their hubs. The contact 174 is in advance of the contact 167, the amount of lead being varied by adjusting the distance between the discs. The discs are moved laterally by the weighted lever mechanism shown from the core 184 of a coil 182 connected to the main 155 on each side of a resistance 183. If the voltage falls, the core 184 is raised by a weight 192, and the discs are moved apart so as to reduce the lead of the contact 174.