GB559244A - Improvements in and relating to electrode feed control apparatus - Google Patents

Abstract

559,244. Automatic control systems for arcs. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 6, 1942, No. 10970. Convention date, Aug. 12, 1941. [Class 38 (iv)] An arc electrode such as 10 is controlled by a D.C. motor the armature 16 of which is supplied from a generator 24 having a control field winding 29 energized in accordance with the difference between a predetermined voltage from a potentiometer 35 and a voltage from a resistance 36 which is connected through a rectifier 34 across the arc. The electrode moves towards or away from the co-operating electrode or work 11 according to the polarity of the voltage difference and at a speed depending on its magnitude. To prevent sticking of the electrode due to excessive forward speed an opposing control winding 31 is energized from the generator through a suitably poled rectifier 32 and means 33 responding to the rise of generator voltage but at a greater rate: The generator is preferably of the kind described in Specification 539,835 having a pair of short circuited aramature brushes 90 degrees displaced from the load brushes and the voltage responsive means 33 may be a non-linear resistance, such as a mixture of carborundum, clay, and carbon as described in Specification 292,110, [Class 15 (ii)]. In a modification, a single control winding 29 is used and an auxiliary generator, excited by a winding connected as the winding 31, is in series with the control winding. The generator may have an auxiliary exciting winding to check hunting, and this may be in parallel with the motor armature through a condenser. Field windings 30 neutralize the armature reaction due to the generator load current. Specification 520,047, [Group XXII], also is referred to.