Patent GB-190821366-A (GB)
Title: Improvements in Electricity Rectifiers.
Inventor: MURPHY THOMAS JOSEPH
Filed: 1908-10-09
Granted: 1909-10-11
Abstract: 21,366. Murphy, T. J. Oct. 9. Converting alternating and direct currents; switches; transformers. - A rectifier comprises two pairs of rotating electrodes 118, 134, 119, 135, Fig. 13, connected to the alternating-current circuit 202 and to a battery &c. 201, and a synchronizer 51, which shortcircuits alternately two pairs of terminals 61, 62 connected to a teaser circuit 163 so as to discharge the teaser circuit across the rotating electrodes, which are normally impassable to the current, and thereby to start the rectifying - arc in synchronism with the alternations. Fig. 13 shows the connexions for rectifying both the positive and negative waves. The electrodes between which the arc is formed comprise positive electrodes 134, 135 of steel, and negative electrodes 118, 119 of carbon. The electrodes are shunted by very high resistances 173, through which pass the " sneak " currents when an arc is started between the opposite electrodes. The electrodes are connected on one side through the coils 17 of an electro-magnetic cut-out 31 to the outside blades of a knife-switch 202 in the alternating circuit that is to be rectified, and on the other side to the return wire in which is placed the battery &c. 201 adapted to take the rectified current. The means for starting the arc is driven by a synchronous motor 51, connected from one main through switch 4, a make-andbreak switch 178, an armature 51, and cut-outs 31, 32 to the other main. The coils 17 of the cut-out 32 are in shunt to the battery 201. The primary 166 of a transformer is connected in shunt to the armature 51, and the ends of the secondary 165 are connected through choke coils 160, 162 to two electrodes 61, 62 mounted in proximity to another pair of electrodes 61, 62 connected to the positive electrodes 134, 135. The middle of the secondary is connected through a choke coil 161 to the return wire. Condensers 163, 164 are connected across the choke coils, which latter serve to protect the teaser circuit. The means for starting the arc consists of a conducting-rod 60 carried by a cylinder 58 of insulating-material secured to the armature shaft, and rotating in proximity to the electrodes 61, 62 and in unison with the alternations. The operation is as follows :-The switches 202, 3; 4 are closed, and the armature is speeded up until it moves synchronously with the alternations. The terminals 61, 62 are then adjusted so that, when the condensers 163, 164, charged by the high potential teaser current, are discharged across the terminals 61, 62 and the conductor 60 and across the electrodes 134, 118 on one hand, and 135, 119 on the other, the potential of the alternations will maintain the arc notwithstanding the counter-electromotive force of the arc and the battery. The arc being formed and maintained, a circuit is completed through the electrodes 134, 118 to the battery 201 during, say, the positive wave, and through the electrodes 135, 119 to the battery during the negative wave, but both currents are directed to the battery in the same direction. By causing the electrodes to rotate, the arc is interrupted at the desired potential and also cooled. The apparatus is mounted on the shelf 99 of a panel 1, on the face of which are mounted the measuring and starting devices and switches. The armature shaft 52, and a shaft 101, Fig. 6, are connected by gearing, and a spring-held lever 11, connected to a crown-wheel clutch 94, operates to speed the armature up to synchronism. The terminals 61, 62 are carried on a wheel 46, and are in proximity to the insulating-cylinder 58 on the armature shaft carrying the conductor 60. The wheel 46, Fig. 4, is linked by a pinion and rod 40 to a toothed wheel 35, operated by a hand-wheel 7, Fig. 5, and locked in position by a toothed foot 5. The shaft 101 drives a hollow shaft 107, Figs.4and8, by means of gearing, preferably of vulcanized fibre, and the shaft 107 drives shafts 132, 133, Fig. 9. The hollow shaft 107 carries the negative electrodes 118, 119 consisting of carbon wheels, and the shafts 132, 133 carry the positive electrodes 134, 135 consisting of a steel ring. The shafts 132, 133 are carried by brackets 141, Fig. 4, connected to a screwed rod 145 passing through a bracket 150, and thumb-screws 148, 149 mounted on the rod enable the distance of the electrodes to be regulated. The shafts 132, 133, 107 rotate at different speeds so that the same portions of the electrodes do not face each other in two consecutive turns, and the opposing faces of the electrodes move in opposite directions. The high-resistance shunts 173 are carried by brackets under the panel 99. The switch 178 comprises two bent arms 177, 178, Fig. 11, pivoted at 182, 183 on an insulating-disk 176 mounted on the shaft 101. The pivots are connected by a strip on the other side of the disk, and the arms are adapted to contact with studs 179, 180 connected to slip rings 184, 185 on the shaft 101 and thence to the external circuit by brushes 187, 188. When the motor is started by rotating the crank 11, the arms fly out and make contact, and, when the motor ceases to rotate, one of the arms drops and breaks circuit. The circuitbreakers 31, Fig. 2, comprise an electro-magnet 17 and armature 18 controlled by a weighted lever 21 and set-screw 23 on a bracket 19. The armature carries an insulating-block 24, which, when the armature is attracted by the coil 17, enters between arms 29 and separates the contacts 30, Fig. 3. The block 24 is held by a latch 25 controlled by a spring 26 and stop 27 on a bracket 28. The latch 25 has an extension 202 ending in a button 201, which, when pressed, releases the armature and block and closes the contacts. The circuit-breakers are mounted on a plate 14 and enclosed in a glass dome. The transformer, Fig. 4, consists of secondary spools 165, and primary spools 166 mounted on a core 167 provided with a cross-piece 169, which shunts the flux when the primary is short-circuited. The choking-coils 160, 161, 162 and condensers 163, 164 rest on the transformer.