By kenmui
Date 11-09-2002 01:48
Generator machines have very low ripple DC ( smooth ) but MORE importantly you can vary the arc charicteristic
by varying the "volt amp cuve" . For example on your machine, you can have 4 different charcateristic arcs
at 125 amps. You are able to play with the arc characterisitic to your likeing
Rectifier machines generally run (their electronics ) at 60Hz and the charactersitic curve is also designed in the machine. Due to the low switching frequency the "ripple" of the DC output is not as smooth , expecially at low output. The try to smooth this with choke and or capacitors. Higher end stick machines will have an arc force control ( NOT the same as playing with the Volt Amp curve, but rather a current bost at low ( shorting ) voltages. As you short out the electrode (push it into the plate ) the Voltage essentially approaches Zero, at that point, the arc force boost the current ( even though it's suppose to be constant current ) effectivly burning the electrode back...cant stick even a 7018 when turned up!! Downside....this also gives the characteristic of a harsher arc ( but not to be confused with playing with the VA reaction as you push the electrode deeper into the joint...the claim to fame for generators )
Inverter machines have much higher switching frequency( 20kHz and up). Because of this you are able to shape the Volt Amp curve to whatever you want. Here is the caveat...not all inverters are created equal.
Most inverters will have a arc force control . Leave this in the lower position if you want a smoother arc. this alone can sofen
soften the arc to your likeing .....but having said that, inverters such as the Lincoln inverters also have two stick settings. They have their "6010" type crisp setting , or their buttery smooth "soft" setting . On top of that you can also tweak the arc force.
Inverters that don't have the two stick settings always have a compromise setting.
For the record, an inverter design can easily approach the "smoothness" of a generator machine....but it's all in the design implementation. If they design it to have a very soft arc, that's what it'll have, but if the design is to have a harsher arc, that's what it'll have !
Hope this helps and didn't bore !
Eric: Sorry that it has taken this long to answer. The current switching speed inside the Pipe Pro is 50 Kilohertz. Because of this speed you can get 400 amps out of a power module that weights only 80 lbs. The rest of the weight is engine and generator.
The dig control when set at "O" will have a very soft mushy arc and the higher you set it the more drive the arc will get. Adjusting the Dig control up does change the VA curve on the lower voltage end of the curve.
As arc voltage goes down below 20 volts the machine will add more amperage to keep the electrode from sticking. So this is like remote amperage control and you control it by varying your arc length which controls the arc voltage. If the joint gets tight pushing the stick in to the joint caused the voltage to go down and the current up. If you were welding at 100 amps and had the dig set at 50% you would get about 50 extra amps when the arc voltage gets down to 15 volts. If you had it set at 100% you could get 100 amps. So each 1% will give you about 1 amp extra if you want it. Now the big difference between a generator machine and the Pipe Pro is how fast this extra current goes away when the voltage goes back up. This arc flair on the inside of the pipe is one of the major causes of internal under-cut. The Pipe Pro will go back to preset current much faster than a Lincoln machine. This reduces internal under-cut.
The Lincoln generator machines would do some what the same thing and you could adjust it to act different. This required playing with the engine RPM'S, welding in a different range or rolling the rack. All these adjustments took time or tools to make the adjustments. The dig control knob is much easier.
I hope that this answers most of you questions.
Mike Brace
