(UK context) How can a domestic Mig Welder be 150A, and work fine on a 13A fused, single phase domestic mains electricity supply?
In: 17
Because welders are very low voltage.
With electricity it is possible to “exchange” voltage for current or vice versa using a transformer.
This is simply because Power In = Power Out, since you can’t make power from nothing, the power that goes in one end of a transformer has to be the same that comes out the other (neglecting losses), and electric power is Voltage x Current.
So if you have a MIG welder running at 150A at 10V that would be 1500 Watts of power, so if the output of the transformer in the welder is 10V and 150A, the input side would have to be exact same power, just at a different voltage, namely 240V. And at that voltage, you only need 6.25 amps to generate the same amount of power, so even though the welder might be running at 150A, the current leaving the outlet is only 6.25A and therefore won’t trip your fuse or breaker
Ohms law: power (watts) = amps x volts. it’ll use a transformer to step up the current from 13amp 230volts to 150amp. If you look I’m guessing the power rating (watts) of the welder is around 3000w? So that should give an internal voltage of 3000/150 = 20 volts
Power (watts) = volts * amps
150amps @ 10volts = 6.25amps @ 240volts
They’re both 1500watts, but converted based from the voltage the wall supplies to what the welder needs.
As others have explained, you can output a higher amperage from the machine that it receives from the wall by changing the voltage. it’s also worth noting that while welding is possible on regular residential 13A outlets it’s actually still very common for them to trip constantly when welding. This can happen either because the electrode on the welder gets very hot or it sticks to the piece you’re welding which causes a huge spike in resistance.
I can’t remember what they said in school but I think inverter-transformer welders are the best kind.
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