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Grahame Collins
16th Jan 2018, 01:54 PM
When welding with an older transformer powered welding unit, one could always notice when the supplied incoming current to the GPO was lacking.

You can picture the scenario, the height of summer, aircon running neighbours swimming pool pumps going, dinners cooking and me, at the end of the dead end street with a welder that ran like a slug. Ok it was obvious, reduced input therefore reduced output.
I have used the multimeter and seen as little as 218 volts at the GPO.


What happens then, with the inverter then especially the ones with a digital readout. If there is significant power supply low voltage situation what is the story with the readout. If the digital readout,say reads 120 amps < edit:sorry senior moment there, I originally wrote volts and meant amps>, can that figure be relied on. Locally we haven't had an obvious low voltage situation for a long while and I have no way of checking.
With a lesser voltage loss than a transformer does the inverter make up for low input power.?

Gavin Newman
16th Jan 2018, 03:48 PM
The display should reflect the true output voltage which should be independent of the incoming mains voltage until the point where the welder shuts down due to low supply volts.

jhovel
16th Jan 2018, 06:09 PM
The display should reflect the true output voltage which should be independent of the incoming mains voltage until the point where the welder shuts down due to low supply volts.

... or rather the output current in Amps - in most cases....

I'm in the same position - on SWER (with many more users on a single wire). We have huge fluctuations - but one on my inverter welder output. Yes, they automatically compensate for a big range of input voltage changes.
I've put a tiny voltmeter on my workshop switchboard to see what's happening - mainly as a result of my own activity ;)

Ropetangler
18th Jan 2018, 06:42 PM
What happens then, with the inverter then especially the ones with a digital readout. If there is significant power supply low voltage situation what is the story with the readout. If the digital readout,say reads 120 amps < edit:sorry senior moment there, I originally wrote volts and meant amps>, can that figure be relied on. Locally we haven't had an obvious low voltage situation for a long while and I have no way of checking.
With a lesser voltage loss than a transformer does the inverter make up for low input power.?

The inverter welders are basically switch mode power supplies, and a simplified explanation of how they work, is the incoming mains power charges a capacitor bank, which supplies the power which eventually powers your electrode holder.
The capacitor bank is charged to a voltage which will enable the required amperage to flow in the welding circuit, and this voltage is controlled by an electronic switch, which switches on and off at a rate such that the voltage is held close to the required voltage.
If the mains power voltage is lower than the ideal of 240 volts, (in Australia), then the electronic switches are on a greater percentage of time than they would be if the voltage had been at 240 volts say to keep the capacitor bank at the required voltage level.
This is a greatly simplified version of what takes place, in reality there are all sorts of refinements to add extra benefits, but it does explain the way an inverter welder works much better with a so so power supply compared to a transformer welder which just reduces the voltage by the same ratio as the turns ratio of the primary and secondary windings of the transformer, so a low input means a low output.:~ I hope that you could follow this waffle, other may give a more succinct explanation than I can:)
Rob.