Direct current power supply for manual arc welding

Abstract

A direct current power supply for manual arc welding having a steeply drooping, adjustable characteristic, comprising a polyphase transformer and a polyphase rectifier system including triggered rectifier means and a control system therefor providing both welding current and welding voltage feed-back. The welding current feed-back is substantially fixed. The welding voltage feed-back is adjustable for adjustment of the slope of the characteristic.

I claim: 
     
       1. A direct current power supply for manual arc welding having a steeply drooping, adjustable volt-ampere characteristic comprising a polyphase transformer having a plurality of secondary output leads carrying mutually phase displaced voltages, a polyphase rectifier system connecting said secondary output leads to a pair of D.C. welding current conductors, said rectifier system comprising a set of triggered rectifier valves connected one in series with each of said secondary output leads, said triggered rectifier valves having each a trigger terminal for initiating current flow through the valve,   means for periodically supplying igniting pulses to each of said trigger terminals, including means for causing the angular position of said pulses to vary in response to a direct current control signal, and,   means for producing said direct current control signal comprising the following means, to wit,   a. means for producing an adjustable direct current reference signal,   b. means including a welding current sensing means for producing a welding current feed-back direct current signal bearing a substantially fixed proportion to the welding current carried by the pair of welding current conductors,   c. means including a welding voltage sensing means for producing a welding voltage feed-back direct current signal proportional to the welding voltage between said welding current conductors,   d. summing means for combining said reference signal, said welding current feed-back signal and said welding voltage feed-back signal into a compound signal constituting the control signal aforementioned, both of said feed-back signals being supplied to said summing means in opposing relationship to said reference signal, said means for producing a welding voltage feed-back signal including means for adjustment of the slope of the volt-ampere characteristic of the power supply through adjustment of the ratio of said welding voltage feed-back signal to the welding voltage independently of the ratio of the welding current feed-back signal to the welding current.   
     
     
       2. A direct power supply having a steeply drooping volt-ampere characteristic for manual arc welding comprising a polyphase transformer having a plurality of secondary output leads carrying mutually phase displaced voltages, a polyphase rectifier system connecting said secondary output leads to a pair of D. C. welding current conductors, said rectifier system comprising a set of triggered rectifier valves connected one in series with each of said secondary output leads, said triggered rectifier valves having each a trigger terminal for initiating current flow through the valve,   means for periodically supplying igniting pulses to each of said trigger terminals, including means for causing the angular position of said pulses to vary in response to a direct current control signal, and, means for producing said direct current control signal comprising the following means, to wit,   a. means for producing an adjustable direct current reference signal,   b. means including a welding current sensing means for producing a welding current feed-back direct current signal bearing a substantially fixed proportion to the welding current carried by the pair of welding current conductors,   c. means including a welding voltage sensing means for producing a welding voltage feed-back direct current signal proportional to the welding voltage between said pair of welding current conductors,   d. summing means for combining said reference signal, said welding current feed-back signal and said welding voltage feed-back signal into a compound signal constituting the control signal aforementioned, both of said feed-back signals acting in opposition to said reference signal in said summing means,   said means for producing a welding current feed-back signal, said summing means, said means for controlling the firing angle of the triggered rectifier valves and said rectifier system constituting a welding current feed-back loop arranged to provide a welding current feed-back factor not less than 1.5 volts per ampere, and   said means for producing a welding voltage feed-back signal including means for adjustment of the ratio of said welding voltage feed-back signal to the welding voltage independently of the ratio of the welding current feed-back signal to the welding current to provide a selected, steep slope of the volt-ampere characteristic of the power supply.   
     
     
       3. A direct current welding power supply as claimed in claim 2 in which said welding current feed-back loop provides a welding current feed-back factor not less than 2.5 volts per ampere.