VRD

The Shed - - Welding -

More elec­tri­cal equip­ment is com­ing out with safety or haz­ard-re­duc­ing com­po­nents and weld­ing equip­ment is no ex­cep­tion. Most welders have had a shock and laughed about it, but it can be se­ri­ous. The volt­age re­duc­tion de­vice (VRD) is to weld­ing ma­chines as the safety airbag is to cars.

VRDs re­duce the haz­ard of elec­tric shock by au­to­mat­i­cally re­duc­ing the open cir­cuit volt­age (OCV) be­tween the weld­ing out­put ter­mi­nals when you are not weld­ing. Weld­ing ma­chines for MMAW and sim­i­lar CC pro­cesses, sup­ply a higher OCV be­tween the elec­trode and the work when the weld­ing ma­chine is switched on and ready to com­mence weld­ing. The OCV is of­ten higher (60–100V) than when the arc is es­tab­lished and weld­ing cur­rent is drawn (15–35V).

Con­se­quently, the great­est dan­ger oc­curs when han­dling the elec­trodes and the elec­trode holder be­tween weld­ing oper­a­tions, such as when chang­ing elec­trodes.

RE­SIS­TANCE

The VRD will re­duce the no-load volt­age OCV to less than 35V for DC weld­ing and for AC weld­ing 35V peak or 25V AC rms (‘root mean square’, the ef­fec­tive value of alternatin­g cur­rent) when the re­sis­tance across the out­put cir­cuit is 200Ω or greater. It must op­er­ate within 0.3 sec­onds for DC ma­chines with an OCV of over 113V peak.

*The ac­tual sever­ity of each ef­fect will de­pend on such things as the phys­i­cal con­di­tion of the work area, the phys­i­o­log­i­cal con­di­tion and re­sis­tance of the body, and the area of the body through which the cur­rent flows. You must con­sider ev­ery volt­age as be­ing dan­ger­ous.

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