Thread: Real Welding Amps - some tests.

Great information. I thought about this when WelderMick posted in my thread about arc control and listed way lower amps than I can effectively use with my Smootharc 130. I suspected my cheap machine might have a weird calibration because of his comments and you've pretty much confirmed it.

Yep, it explains a lot when I've used thinner rods on the BOC 130 - it turns out I might have dialled in 60 amps, but I'm actually trying to weld with as low as 50 amps.

That's great information Rusty, thanks for posting....

So out of curiosity - with the SmoothArc. Does the current go up with the longer arc length or decrease? What are your observations with the actual heat in the weld with short versus long arc?

Cheers

- Mick

Originally Posted by WelderMick

So out of curiosity - with the SmoothArc. Does the current go up with the longer arc length or decrease? What are your observations with the actual heat in the weld with short versus long arc?

I'll have to do some more tests to confirm this, but from memory the current increased as the arc shortened, and with more current flowing, I'd expect more heat as a result, but that's something I'll confirm when I get a moment.

I'm still surprised at just how different the current behaviour is between the two welders - I'd never have guessed from using them, although now I know, when I'm welding with either machine I'll be thinking about how the current management actually affects welding behaviour.

Having had used a multitude of different welders, brands, power sources and rod brands, I have found that the calibration marks on the machines are an indication only. You will need to fine tune the settings as to the time of day, rod size, brand, type, and power source.

I have found that if it feels right, it usually is.


Robert

Good post Rusty
With stick welding

Long arc length - decreasing current - Higher voltage-arc pool flat and hot

Short arc length - increasing current - Lower Voltage - arc pool narrow and colder

That was for transformer welders and I have no information that tells me that the basics might have changed.

What breed is Your clamp meter.I wanted an AC/DC model but it was very expensive.

Grahame

Originally Posted by Grahame Collins

That was for transformer welders and I have no information that tells me that the basics might have changed.

What breed is Your clamp meter.I wanted an AC/DC model but it was very expensive.

Next time I run some tests I should measyre voltage too - it's a bit more involved, but should be possible I think.

The UniMIG must be varying the voltage significantly to maintain its near-constant current. The BOC, not so much I suspect.

I spent a while choosing a DC-capable clamp meter - in the end I went for a true RMS model as it'd be useful for measuring AC current on inverter-type supplies used for all manner of machines these days such as variable-speed pumps and inverter air conditioners.

Jaycar do a Chinese no-name unit for about $140 or so, but I went with a US unit - AEMC - from Trio Smartcal who deal in quality test equipment (and calibration). With freight it cost about $260:

TRIO Smartcal Pty Ltd

Apart from the true RMS bit, it has a 1ms peak measurement which is handy for catching high startup currents, such as the DC motor I'm working with which clocks in at 540A as it starts.

For most purposes, though, I suspect the cheaper Jaycar unit would do just fine. They also do a non RMS unit for about $120 which would also be fine for the output of ordindary (non HF TIG) AC and DC welders.

Originally Posted by RustyArc

I'll have to do some more tests to confirm this, but from memory the current increased as the arc shortened, and with more current flowing, I'd expect more heat as a result, but that's something I'll confirm when I get a moment.

Yeah, that's what I would've expected - so the actual power output remained the same, with just the voltage and amps changing in response to the changed resistance over the arc gap.

I though Amps = Heat, So if more current flows with a small gap, then this would imply more heat, which seems contrary to Grahame's post as well as practical experience which indicates you should maintain a short arc to avoid burn through on thin metals, vertical up welding etc...

I'm also trying to work out the 1/3 vs 2/3 heat versus polarity thing - why is this so?

Anyone care to explain the science in this?

Cheers

- Mick

Interesting . Would also be interesting to see how much the drop is if running the welder on a couple of long extension cords and also heavy use on a very hot day .It seems under those conditions there is a lot of drop and the dial needs to be turned up quit a bit to compensate.Also if the work clamp on a big job is a long way from the arc it might read a lot lower .
Keep up the good work ----mat---

Volts = Heat
On a MIG machine the voltage adjust is often referred to as the Heat setting.

(Mig = constant-voltage device Vs Stick = constant current)