Patent GB-190006568-A (GB)
Title: Improvements in or relating to the Heating of Conductors of the Second Class in Electric Incandescent Lamps
Inventor: RAAB CARL
Filed: 1900-04-07
Granted: 1901-03-16
Abstract: 6568. Raab, C. April 7. Incandescent lamps. -Incandescence bodies, which conduct only after preliminary heating, are connected between the main wires and neutral wire of a three-phase or three-wire system, or between the wires of a twowire system, and are started by electric heaters inserted in series or otherwise in the neutral wire, which in a two-wire system is the bridge wire of a quadrilateral arrangement of resistances connected between the main wires. The arrangement is such that, when the incandescence bodies are normally conductive, the combination is balanced electrically, so that no current passes through the neutral wire and heaters. At starting, the electrical balance is disturbed in various ways to cause passage of current through the neutral wire and heaters. The resistances may be such as to become hot and of higher resistance when carrying current. With alternating currents the resistances may be inductive, or replaced by condensers, and the heaters may be supplied through transformers from the neutral wire. The heaters may consist of thin platinum wire wound on mica. A three-phase arrangement is shown in Fig. 4. Three incandescence bodies 25, 26, 27 are connected between the three mains and the neutral wire, which contains the three heaters 30, 31, 32 ; at starting, a resistance 28, such as an ordinary incandescent lamp, is temporarily connected in parallel with one incandescence body 27 by a hand or automatic switch 29. In a modification of this arrangement, the incandescence body 27, resistance 28, and switch 29 are replaced by an ordinary incandescence lamp, which remains in circuit after starting, the heater 32 being omitted. More incandescence bodies may be connected symmetrically between the three mains and the neutral wire, all the heaters being in the neutral wire. Switches may be provided to short-circuit the heaters, for use successively. A three-wire arrangement is shown in Fig. 11. Two incandescence bodies 97, 98 are connected between the two outer wires and the neutral wire. After starting, the two outer wires are connected together through a resistance 96, a movable core 95, a contact-screw 94, and a solenoid 93, and the heaters 90, 91, being connected between the middle 92 of this circuit and the neutral wire, receive no current. At starting, the core is not in contact with the screw 94, and current passes through the heaters from one outer wire. The rise of the core into the solenoid is retarded by enclosed air, a pendulum escapement, or electrodynamically or otherwise. A slow-acting thermal switch may be substituted. A two-wire circuit may have its mains connected by two circuits through resistances, cores, and coils such as those shown in Fig. 11, these circuits being arranged oppositely to one another ; the heaters are connected between their middle points 92. After starting, both circuits may be disconnected by a switch, the incandescence bodies being directly between the mains. A two-wire alternating- current circuit may be connected as shown in Fig. 8. A differential choking coil is used, having two coils 56, 57 wound oppositely to a third coil 59, on one core. The coils 56, 57 are in series with two'incandescence bodies 55, 54, and, when these are conducting current, no current passes through the bridge wire containing the third coil and heating-wire 58. At starting, current passes through the heating-wire and all three coils so that their inductive resistance is reduced to a minimum, and a large heating-current is obtained.