GB894646A - Carbon arc lamp with automatic carbon advance - Google Patents

Abstract

894,646. Automatic control systems for arc lamps. BAUER G.m.b.H., E. Sept. 25, 1959 [Sept. 27, 1958], No. 32600/59. Class 38 (4). [Also in Group XL (a)] An automatic control-system for a carbon arc lamp comprises a first control means for advancing the positive carbon in response to the position of the arc, a second control means for advancing the negative carbon in response to the voltage across the arc, the two means being so interconnected that the second control means is disabled whilst the first system is operative. An arc is struck between carbons 3, 5 by manual means whereupon relay coil 101 is energized to close contact 102. The field winding 111 of the carbon advance motor is thus energized directly from positive line 98, the armature 107 of this motor being supplied from the same line over resistors 105, 106. Thereupon the motor rotates very slowly, the positive carbon 3 then being advanced at a very slow rate whilst move ment of the negative carbon 5 is prevented by an electromagnetic lock 65 energized over contact 139 of a relay 136. Under these conditions the advance of the positive carbon does not fully compensate for the burning away of the carbon. At some point the light rays from the arc affect a photo-resistor 84 which becomes conductive to energize a relay coil 90 whereupon contact 92 changes over from contact 94 to contact 93. The field 111 is now supplied over resistor 109, causing field weakening, and resistor 105 is removed from the circuit of the armature 107. The motor now runs at a high speed to quickly advance the positive carbon until the light rays from the arc no longer impinge on the photo resistor 84 which then becomes non-conductive to de-energize relay coil 90 and the contact 92 returns to its original position. Whilst relay coil 90 is energized no movement of the negative carbon is possible since relay 136 cannot be energized under this condition. When relay coil 90 is de-energized should the arc length, and hence arc voltage, become too large sufficient voltage will appear at the points 125, 127, a sensitive relay coil 131 is energized to close contact 138 to energize the relay 136 to open its contact 139 thus deenergizing the lock 65 whereupon the motor is able to slowly advance the negative carbon until the arc voltage is returned to normal. Relay coil 131 is then de-energized and the lock 65 reapplied. Relay 121 protects the sensitive relay 131 against excess voltage. Resistors 116, 117 are oppositely temperature-sensitive and serve to prevent operation of the relays controlling the advance of the negative carbon when the arc lamp is cold.