Page 1 of 1
Information on Dc Offset?
Posted: Sat Oct 16, 2021 4:13 pm
by FranG
So I have recently gotten into a welding program and have been doing it for about 2 months now. Been doing Tig welding in aluminum (AC HF), and have always seen this setting on this machine called Dc Offset next to other settings like (Ac Balance & Hz).
Can someone please explain to me what Dc Offset is, and what it does? I’m very curious, I’ve only just started playing around with it. thank you!
Re: Information on Dc Offset?
Posted: Wed Oct 20, 2021 2:39 pm
by Toggatug
I've never heard of or seen a setting like that.
Could you post a picture of the machines face and list the make and model of machine?
I probably still won't be able to help but its one of the first questions I see asked by the people more knowledgeable then me on this forum.
Sent from my Pixel 3a using Tapatalk
Re: Information on Dc Offset?
Posted: Wed Oct 20, 2021 6:44 pm
by Jack Ryan
FranG wrote: ↑Sat Oct 16, 2021 4:13 pm
So I have recently gotten into a welding program and have been doing it for about 2 months now. Been doing Tig welding in aluminum (AC HF), and have always seen this setting on this machine called Dc Offset next to other settings like (Ac Balance & Hz).
Can someone please explain to me what Dc Offset is, and what it does? I’m very curious, I’ve only just started playing around with it. thank you!
What is the machine? Can you provide a link to the manual?
On some machines, you can independently set the magnitude of the DCEP and DCEN sections of the waveform. A simpler version of this is to add a DC offset. But that is just a guess - a manual is needed.
Jack
Re: Information on Dc Offset?
Posted: Wed Oct 20, 2021 7:55 pm
by Oscar
Jack Ryan wrote: ↑Wed Oct 20, 2021 6:44 pm
FranG wrote: ↑Sat Oct 16, 2021 4:13 pm
So I have recently gotten into a welding program and have been doing it for about 2 months now. Been doing Tig welding in aluminum (AC HF), and have always seen this setting on this machine called Dc Offset next to other settings like (Ac Balance & Hz).
Can someone please explain to me what Dc Offset is, and what it does? I’m very curious, I’ve only just started playing around with it. thank you!
What is the machine? Can you provide a link to the manual?
On some machines, you can independently set the magnitude of the DCEP and DCEN sections of the waveform. A simpler version of this is to add a DC offset. But that is just a guess - a manual is needed.
Jack
I agree that is most likely what it is.
FranG,
As others have said, please post them the machine make & model, so the manual can be found.
Re: Information on Dc Offset?
Posted: Wed Oct 20, 2021 8:17 pm
by sbaker56
Yep manual needed, I concur with both posters above as to what it most likely means, but it's definitely a question id want to see the manual to be sure of my guess.
Re: Information on Dc Offset?
Posted: Fri Oct 22, 2021 12:24 pm
by BugHunter
DC Offset is exactly what it implies, a DC component on an AC waveform. Very common in electronics, especially things like POE devices (power over ethernet) where the signal and the power are coming in on the same wire. They stick say 5v or 12v dc on the wire but they also multiplex the data signal in as an AC waveform. So what you do is use a comparator which takes a sample 5v or 12v signal and compares to what is on the line. The difference is the data.
On a welder, the same principal applies. The DC component is supplying En/Ep current, but the Ac component also allows for cleaning action at the same time.
So, I'll just use hypothetical numbers here. Let's say there's an AC signal with 20V of amplitude and a DC 10V signal multiplexed in as the offset. On an oscilloscope what you see is an AC waveform that varies from 10V to 30V. In what application that is used when welding I do not know, but I suspect it benefits when doing heavy aluminum welding.
Re: Information on Dc Offset?
Posted: Fri Oct 22, 2021 4:17 pm
by Oscar
BugHunter wrote: ↑Fri Oct 22, 2021 12:24 pm
Let's say there's an AC signal with 20V of amplitude and a DC 10V signal multiplexed in as the offset. On an oscilloscope what you see is an AC waveform that varies from 10V to 30V. In what application that is used when welding I do not know, but I suspect it benefits when doing heavy aluminum welding.
The only issue with that description is that the "typical" offset in a welder that has independent amplitude control doesn't exhibit
that kind of shift. If the whole waveform happens to shifs over, and the trough (or peak) is shifted enough to lie "on the other side", then one of the standard polarities (either the EN or the EP, depending how the offset occurs), disappears, and the actual arc behavior would be pulsing up & down on one polarity only, with the direction of the electron flow not actually changing, only varying in magnitude, because the reference ground has not shifted. So, with enough offset using that description, one could change AC into DC-pulse (again, with enough of an offset). I don't think this is the case with any welder that has this feature. It just doesn't make sense to my mind.
Re: Information on Dc Offset?
Posted: Fri Oct 22, 2021 8:56 pm
by Jack Ryan
BugHunter wrote: ↑Fri Oct 22, 2021 12:24 pm
DC Offset is exactly what it implies, a DC component on an AC waveform. Very common in electronics, especially things like POE devices (power over ethernet) where the signal and the power are coming in on the same wire. They stick say 5v or 12v dc on the wire but they also multiplex the data signal in as an AC waveform. So what you do is use a comparator which takes a sample 5v or 12v signal and compares to what is on the line. The difference is the data.
On a welder, the same principal applies. The DC component is supplying En/Ep current, but the Ac component also allows for cleaning action at the same time.
So, I'll just use hypothetical numbers here. Let's say there's an AC signal with 20V of amplitude and a DC 10V signal multiplexed in as the offset. On an oscilloscope what you see is an AC waveform that varies from 10V to 30V. In what application that is used when welding I do not know, but I suspect it benefits when doing heavy aluminum welding.
The AC and DC signals are added rather than multiplexed.
A common AC welding current is a square wave - it has equal magnitude DCEP and DCEN half cycles centred on zero amps (the average current is zero amps). When the AC balanced is changed, one half cycle becomes longer and the other shorter. This is used to vary the amount of cleaning compared to the amount of penetration.
When a DC offset (limited to the peak magnitude of the square wave) is added, the magnitude of the cleaning cycle compared to the penetration cycle can also be varied. This can be used to retain penetration while increasing cleaning or vise versa. Some welders have independently adjustable DCEP and DCEN half cycles instead but the result is the same.
There are other applications as well. Changing the ratio of RMS to mean current varies the penetration and bead width.
However, without a manual, this is still a guess.
Jack