
Pulse in DC TIG
You typically use the DC pulse function to re uce the heat input when wel ing to prevent istortion
or excessive iscoloring of the base metal. The Amperage isplay shows the maximum amperage,
an you set the backgroun amperage an the peak time (pulse-on time or uty) base on that
maximum amperage. You set both the backgroun amperage an the peak time as a percentage of
the maximum amperage. Peak time refers to the peak pulse current number. The actual uration of
the peak time, in secon s or in fractions of a secon , epen s on the thir variable—the pulse
frequency. The pulse frequency etermines the spee , for lack of a better wor , of the time it takes
to switch between the higher an the lower amperage. There are two schools of thought:
• Use low-spee pulse frequencies between 0.5 an 2.0 PPS (pulses per secon or Hz) to create a
ripple effect in the wel bea . The pulsing can easily be seen by the human eye. When using low-
spee pulse frequencies, you typically will not experience any interference or other technical
ifficulties with either fixe sha e or auto- arkening wel ing helmets.
• Use high-spee pulse frequencies between 25 an 100 PPS to create a smooth wel bea , much
like DC TIG without pulse. The pulsing usually cannot be seen by the human eye. You typically use
high-spee pulse frequencies when wel ing stainless or mil steel out of position, when heat
affecte zones nee to be kept to a minimum, or when warpage or istortion of parts are a concern.
When using auto- arkening wel ing helmets, epen ing on the frequency of the cartri ge in the
wel ing helmet an the frequency you set the machine to, there may be a very narrow ban of
specific frequencies where interferences are possible. Whether interferences happen at all, or at
what frequency the interferences occur at, epen s on the wel ing helmet you use (make, mo el,
etc.); we cannot pre ict who will experience interferences. If, when wel ing, you notice flickering,
change your frequency by +/- 20 PPS an try again.
For most applications, we recommen setting the backgroun amperage to 25% an the peak time
(pulse-on time or uty) to 25%. Example: You set your max amperage to 100 amps, your
backgroun amperage to 25%, an your peak time to 25%. For 25% of the time, you wel at 100
amps, an for 75% of the time, you wel at 25 amps.
Using these settings uring a low-spee pulse application (with the right torch movement an either
no filler or while using a lay wire technique) allows you to pro uce nice ripples. Using these
settings uring a high-spee pulse application allows you to achieve penetration close to what 100
amps of straight DC gives, but with significantly lower heat input an a much more controllable
pu le. Even though you only reach 100 amps 25% of the time, an 25 amps 75% of the time, in a
high-spee pulse scenario it is NOT safe to assume that the first quarter at 100 amps an the secon
through fourth quarters at 25 amps equal 43.75 amps of overall heat input (100 + 25 + 25+ 25 =
175/4 = 43.75). While the math oes not hol true in high-spee pulse applications, the math comes
a lot closer in low-spee pulse applications. In a high-spee pulse application, at a 25 PPS pulse
frequency setting, you intro uce 100 amps into the base material 25 times per secon , an at a 50
PPS pulse frequency setting, you intro uce 100 amps into the base material 50 times per secon .
Even though this occurs for a short or a very short perio of time, the time between the 100 amp
bursts is not long enough to let the material really cool own to an average of 44 amps of heat input.
Nevertheless, a high-spee pulse application is significantly cooler than just DC TIG.
The strongest effects an the best results occur when you set the ifference between the peak
amperage an the backgroun amperage rather high. With the Revolution 2500, you can a just the
pulse frequency from 0.4 to 1000 PPS, the backgroun amps from 10 to 90%, an the peak time
(pulse-on time or uty) from 10 to 90%.