Abstract of paper presented at the 36th AnnuatConvention of the American Institute ofElectrical Engineers, White SulphnrSprings, W. Va., July I, 1920.

Copyright 1920. By A. I. E. E.

ELECTRIC ARC WELDING APPARATUS

BY ROBERT E. KINKEADLincoln Electric Co.

T HE characteristic of the are obtained upon anelectric arc welding machine determines to alarge extent the utility of that particular

machine for electric arc welding purposes. There hasbeen considerable discussion concerning the relativemerits of the "long arc" and the "short arc" machines.Any arc which is sufficiently flexible to permit

welding on a commercial scale can be held at such alength by the operator that poor welding will be theresult. The 35-volt type of equipment with carbonpile rheostat, the self-excited individual units havinga differential series field, and the alternating-currentequipment have what is called a "short arc." It is afact, however, that a sufficiently long arc can be heldon any of these machines to give very poor welding.The term "short arc" is erroneously applied to thisequipment for the reason that if the arc is suddenlylengthened it will be broken. On the other hand,if the arc is slowly lengthened these machines canfurnish the increased voltage required to maintainthe arc.The variable-voltage type of equipmcint, having

separately excited main field, differential series andstablizer is sometimes referred to as a long arc machine.In the case of this type of equipment, the arc willnot be broken by suddenly increasing its length forthe reason that the induced voltage from the stabilizerwill keep the arc in operation until the increasedvoltage from the welding generator is obtained.From the above analysis it is evident that the con-

troversy over the "long arc" or the "short arc" asapplied to welding machines is in fact a controversy

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over the relative ease of operation and speed of oper-ation of the several types of welding equipment.No entirely satisfactory method of rating electric

arc welding machines has yet been evolved. Ingeneral there are two methods of rating weldingmachines at the present time. The older methodof the two is to rate the machine in amperes the machinewill deliver as continuously as is required for weldingservice without destructive heating of the machine.The later method is to rate the machine in amperes itwill deliver for welding service for from thirty tosixty minutes.

It has been suggested that the welding machine berated in kilowatt output at the arc. This plan doesnot overcome the difficulty, for the reason that it doesnot indicate how much work can be done with theequipment per unit time, nor does it indicate whetherthe machine is rated for metal electrode service orcarbon electrode service or both.

It has been proposed that the welding machine berated in heat units which the machine will make avail-able for welding purposes. Since the welding machineis merely a device for converting electrical energy intoheat, this plan is certainly logical.

Another proposal is that the welding machine berated in number of pounds of metal deposited per hour.This would seem a logical basis upon which to rate amachine for the reason that practically all weldingdone with the electric arc process consists of merelydepositing metal. A rating based on pounds of metaldeposited per hour would be affected by the character-istic of the arc which would be desirable since it wouldgive the user an idea of how much work he couldexpect from the machine.From the above it is evident there are some serious

difficulties in the way of attempting to rate a weldingmachine on the basis of how much work it will do,although it is certainly not beyond the range of pos-sibility that this desirable end may ultimately bereached. It cannot be questioned, however, but thata distinct advantage would be gained by the users ofwelding equipment if the manufacturers of it wouldadopt some uniform method of rating the equipment.