GB952683A - Control and regulating system for arc-welding equipment, more particularly stud welding equipment with power regulation - Google Patents

Abstract

952,683. Control circuits for arc welding. PECO VERKAUFSGESELLSCHAFT. Feb. 2, 1962 [Feb. 21, 1961], No. 3987/62. Heading H2H. The welding time of a stud welding gun P is automatically regulated according to the welding current by a circuit comprising a measuring resistance R M feeding a first electronic lime stage Z n which controls a contactor G through elements S T and which is adjustable to vary the welding time according to the workpiece dimensions, e.g. stud diameter or cross-section. The adjustment of stage Z II is coupled to that of a second time stage Z 1 having maximum time values corresponding to minimum permissible values of welding current, the arrangement ensuring that if, in a particular case, the stage Z II does not open contactor G within the maximum time determined by stage Z I , this opening is effected by stage Z I which also initiates a warning signal and/or prevents any further welding operation. The equipment is supplied through a power unit N, Fig. 2, closure of main switch S energizing a relay M whose contact M 1 controls the gun coil P sp and contactor G, and whose contact M 2 controls the time stage Z 1 . Operation of the gun trigger D energizes a relay E to complete a circuit including a choke D r and a relay F which, if the current is sufficiently high, operates to start the time stage Z I (through contact f 2 ) and to hold relay E energized until contactor G is operated, in the event of premature release of the trigger D. In time stage Z I a transistor T 1 blocks and a transistor T 2 conducts, so that a relay H is energized to close an interlock contact h 1 , to close a contact h 2 and so energize relays A, B, thus lifting the gun P and closing contactor G, and to close a contact h 3 and so start the time stage Z n . The volt drop across resistance R M is stepped-up through a D.C. transformer comprising transistors T 3 , T 4 and an associated transformer, and then fed to the stage Z 11 in which the time taken for a condenser C 2 to charge to a certain voltage depends on the setting of a switch S 2 and on the voltage received from resistance R M . When condenser C 2 reaches the appropriate voltage, a four layer semi-conductor diode T 5 conducts and the resultant pulse is amplified by transistors T 6 and T 7 to energize a relay I, which switches off relays A, B and thus de-energizes gun coil Psp and opens contactor G. Relay I remains energized until relay H is de-energized due to condenser C 1 charging up, and the relay E is switched off (when contactor G closes) by energization of a relay L which remains energized until the gun trigger D is released, whereupon another welding operation can be initiated. If the welding current is too low the condenser C 1 charges up before condenser C 2 and deenergizes the relay H which switches off relays A, B to terminate the weld, the de-energization of relay H before relay B causing a condenser C 3 to discharge through a relay K whose consequent energization switches on a warning lamp W and switches off the relay M. The relay K is self-holding and thus another welding operation cannot be initiated until it has been released by operation of a key T. Condensers C 1 , C 2 are charged through resistors R 1 , R 2 whose values are selected by the setting of the switch S 2 which is coupled to the switch S 1 . If desired, the relay K may operate only the lamp W or the relay M. A modification is mentioned, but not described, in which protection is also provided against excessive welding currents by effecting a minimum time setting corresponding to a maximum current value.