A microprocessor-controlled are welding power supply is disclosed. A silicon controlled rectifier ("SCR") bank is used to generate a direct current arc welding current under program control. Positive synchronization is provided by the microprocessor using a phase locked loop and a polarity detector, so that the gating signals applied to the SCRs are correctly timed. Optimum tradeoffs between hardware and software are accomplished by using look up tables to store correction factors that can be quickly accessed during execution, and by using timers as smart interface chips to fire the SCRs at the same angle during each cycle until changed or updated by the microprocessor. The arc welding power supply is capable of operating in a constant current or constant voltage mode without rewiring the circuit.

Microprocessor controlled welding apparatus

A constant current arc welder of the type in which arc current is regulated by thyristor phase angle adjustment, includes voltage feedback voltage control and current feedback current control, with automatic transfer from the voltage control mode into the current control mode when current has been established in the arc. A time delay allows smooth transfer to the desired current operative level by limiting the current inrush under an initial current reference and with a chosen feedback control dynamic characteristic current boost is also automatically provided when the arc voltage falls below a predetermined level.

Constant current arc welder

The welding head is arranged in a tipping yoke which is secured in a pivot in the frame and can be swung about the pivot. The frame has centering points and can be moved vertically, thus ensuring three-point support. Specifically the welding head can be moved in three directions. Use relates to welding reinforcements to wagon sides.

Arc welding apparatus

An automatic presettable welding system which enables the user to preset the arc voltage and wire feed speed to precise predetermined values without either energizing the wire with arc voltage or initiating the wire feed. A meter (A) is supplied with an appropriate signal so the readout corresponds to the desired wire feed speed or the desired arc voltage and these same signals are supplied to wire feed speed or arc voltage comparative circuits (C, E) which then function to energize a wire feed motor (B) or an arc welding power source (H) to the precise wire feed speed or arc voltage indicated on the meter. Means are provided for controlling the acceleration of the wire feed drive motor and a controlled initiation of the arc voltage at the beginning of each weld. Overload, overvoltage and undervoltage or over or under wire feed speed and other protective circuits (G, F) are provided with appropriate delays in the functioning thereof to ensure fully automatic and satisfactory welding.

Automatic presettable welding system

A process for adjusting a welding torch with respect to a weld joint formed between two workpieces is disclosed, including determining operating quantities for arcs located in at least two positions relative to said weld joint, deriving characteristic values for each of those operating quantities, mathematically combining such characteristic values, and comparing the mathematical combination with a theoretically calculated value for such characteristic values, and then adjusting the position of the welding torch in accordance with the difference between the mathematical combination of those characteristic values and their theoretically calculated value. An apparatus for effecting such welding torch adjustment is also disclosed, including means for adjusting the welding torch relative to the weld joint, means for producing welding arcs between the welding torch and at least two locations with respect to the weld joint, means for determining characteristic values corresponding to operating quantities of the welding arcs, computer means for mathematically combining those characteristic values, means for comparing the mathematical combination of the characteristic values with a theoretically calculated value for the combination of those characteristic values, in order to produce an output signal corresponding to the difference between those values, and means for controlling the means for adjusting the torch relative to the weld joint in response to that output signal.

Method and apparatus for arc welding

A three phase electric arc welding power supply using SCR rectifiers for output control which has improved output characteristics, fault protection and current and voltage controls. The main power transformer includes two secondaries connected in a double wye with the neutral points supplying power to one of the output terminals a pair of independent inductances are in series, one with each set of secondaries. Increased phaseback of the SCR's may be effected without the use of additional inductance in the output circuit. The fault protection circuit has a time-current trip curve closely approximating the time-current overload curve of the SCR's whereby the minimum size SCR's for a given maximum current output is obtained. The control circuit is fast responding and gives either: constant voltage output; or variable voltage, constant current output with both line voltage compensation and with increase of current when the arc is shorted and the arc voltage drops below a predetermined amount. Improved firing circuits for the main and pilot SCR's are provided.

Electric arc welding power supply

A multi-phase SCR-rectifier controlled arc welding power source having improved operating and internal protection characteristics. The transformer has an improved core and winding design having a built-in internal reactance and a core arrangement which is scrapless and very compact. The output has an adjustable, drooping, volt-ampere curve such that the welding current may be readily preset or adjusted to any desired value. The power source includes an unusually high inductance for a three phase source so as to give a very stable arc with a control circuit having provisions to properly control the conduction angle of the SCR's so as to overcome the disadvantages of such a large choke on starting or short circuiting so as to give optimum welding characteristics. Further the ratio of short circuit current to welding current is controlled and decreases with an increase in the welding current. Protection against damage of the power source is provided in the event of extended short circuit or overload. Compensation for line voltage variation is also provided.

Kenneth Anthony Golonka

Papers

Electric arc welding power supply

Arc-welding power source