Hello all.
They were big monsters :



And now I see these :



Can someone explain ? Are these 'chinese amperes' ?

 

Hello,

The old ones used a huge transformer.
The new ones are likely switch mode power supplies.

Bertus

 

Hi.
As a teenager, once saw in a third world country, a welder using the electrode in series to 120VAC and a spring bed base. What was going on ? Plain current limiting ?

Live 120VAC------------bed frame------------arc electrode----------->work piece-----------neutral
Or perhaps
Neutral -----------------bed frame-------------work piece<---------arc electrode-------------120VAC

 

With SMAW welding, it requires the voltage to collapse once the arc is struck, may be a crude way of doing it ??

 

"What is the trick?"

IGBTs.

 

Arc welding is not simple! First, there must be enough voltage to strike the arc, then immediately there must still be enough voltage to maintain the arc while there is enough current to provide the wattage (POWER) to melt metal to create the weld. Not as easy as it sounds, if the goal is good weld quality. THAT SOUNDS COMPLICATED BECAUSE it IS complicated. Certainly there are quite a few people skilled enough to consistently produce very good welds consistently. I am not one of them. But with a decent wire-feed, gas shielded welder I have producedadequate welds.

 

Arc welding is not simple! First, there must be enough voltage to strike the arc, then immediately there must still be enough voltage to maintain the arc while there is enough current to provide the wattage (POWER) to melt metal to create the weld. Not as easy as it sounds, if the goal is good weld quality. THAT SOUNDS COMPLICATED BECAUSE it IS complicated. Certainly there are quite a few people skilled enough to consistently produce very good welds consistently. I am not one of them. But with a decent wire-feed, gas shielded welder I have producedadequate welds.

Was he asking about small welds, or small welders?

 

I believe he was comparing the old 50hz/60hz welders to the modern inverter style, where the AC is converted to DC and electronically controled,
He show both in the OP.
In the case of the older mains transformer style, the secondary was loosly coupled to the primary, typically by a hand cramked coupling section of the transformer, etc.
This done in order to get the voltage collapse at arc strike.

 

Those old Hobart units were beast. Units like the one posted normally used Onan or Wisconsin engines, among the best made, especially during the 60s and 70s.

Ron

 

That big ol inverter has inertia and ride thru properties the smaller electronic version will never have - this makes the big unit suitable for powering a welder or a fridge/freezer which has a 5x current requirement for 5sec for start of the fridge motor.

If that unit is a welder and not simply an AC generator, then the 50Hz transformer needed to step down to 70V ac open circuit and maybe 200A weld current ( 5V ) is quite large by nature of the 50Hz transformer used. Modern inverters chop up the mains at 20kHz - 50kHz and are able to use a smaller transformer to step down the volts and isolate from the mains ( safety ), many also rectify for DC welding.

 

Hello all.
They were big monsters :
View attachment 365827


And now I see these :
View attachment 365828View attachment 365829
View attachment 365830

Can someone explain ? Are these 'chinese amperes' ?

The field welders dream. Lite weight and doesn't require power. But doesnt perform either! Performance comparison ... beyond not even close.

 

If that unit is a welder and not simply an AC generator,

It's a welder manufactured by Hobart. The name Hobart is partially viewable in the image posted.

Ron