High Frequency arc Stabilizer

[Hawkeye]

I picked up this Century HF Arc Stabilizer earlier this week at an estate sale. It is a Model 115-007. Output is 3500 volts and the unit is rated for a maximum welder output of 295 amps.


Has anyone had any experience with this type of equipment? I found the manual, but it consists of a few lines on connecting and a whole bunch of the usual dangers of welding, plus high voltage issues. I'm planning to use it with my Century 70 amp inverter or, to play with aluminum, a 90 amp transformer stick machine.

I have already made a module to provide post-flow argon timing when the arc is extinguished and can expand that to give a choice of continuous HF or start-only.

I've read references to adding capacitors between the supply welder and the HF unit to protect the supply. Do you have any links that go into detail? I imagine the cap would have to be able to handle 5 kV (3500 v x 1.414), but how much capacitance is required? There is no mention of the frequency for this particular unit, but I read a blurb on another one that said 20 kHz. Where is the capacitance connected? Across the output terminals of the welder?

Thanks for any help you can give me.

BTW, if you are using a scratch-type TIG setup, you can use a piece of tungsten clamped near your starting point to reduce or eliminate contamination caused by contacting the steel or aluminum work piece. Just scratch the torch tungsten against the clamped piece to start the arc.

 

[November X-ray]

I have an old Miller Radio Wave (High Frequency) Generator and is basically the same unit. On it, it has built in capacitors that keep you from back feeding the power source, and I remember the manual gave parts numbers for these but I highly doubt I can find it anymore. It has settings for AC & DC and Frequency Adjustment but quite honestly I have not used it in 25 + years. As far as scratch starting goes, it depends on your base material, the amperage you are using and the technique used to ensure no tungsten inclusions occur. We used to use a "sacrificial" electrode where it was really critical. However with the advent of the high frequency unit super-imposing the high voltage in the process, there is no longer any need to "scratch" start.

Oh, one other thing, On the highest voltage setting it can and will arc thru a person's glove, thru your finger, thru the other side of the glove and into the base metal. I can tell you from first hand experience that it is an extremely painful occurance and it took forever for my finger to quit hurting.

 

[Hawkeye]

Thanks for the warning on the fingers. Mine has no frequency or voltage adjustments, but I think 3500 volts could find its own path. I'll try not to be it.

 

[Joe in Oz]

Hang on, HF is not meant to do ANYTHING to a person's tissues (e.g. fingers) the little current that it carries should flow only on the surface.

Yes, mine will arc onto my hand and give me the occasional startle, and if you grab the electrode (making good contact) it will spark from your skin elsewhere on your body to any good ground (surprising sometimes which part of your body is ACTUALLY closest to "ground"). But it doesn't injure me - or cause pain! I guess you could burn yourself eventually if you put up with the spark and keep it going for a long time....
Something is wrong with your HF attachment November-Xray - I suspect.

 

[Joe in Oz]

Just to confirmRick - I am actually a nurse, with lots of industrial accident and electrical experience (the latter from an engineering background in a previous career).
We are possibly talking about several different things here - HF is conducted quite differently to low frequency or DC currents. That topic is however way outside this forum.
If the HF from an arc welder injures you, there is something wrong with the HF unit (probably too low a frequency) and it won't work properly as a pilot arc or HF overlay for aluminium welding.

Let's just say that sparks (think in terms of static electricity) can startle you and go across large distances, gloves an all and acrs can burn your skin, no matter what the current is. Low frequency and DC voltages can injure your tissues by damaging cells inside and outside your body - including cooking your tissue, if sustained long enough with a high enough current (which depends on voltage of course). Incidentally, if you have metal spinters in your scin (from burrs or swarf for example) you will feel MUCH lower voltages - down to 12 V even - as a noticable electric shock - I know that from experience!

Cheers,
Joe

 

[geotek]

The purpose of the HF (they call it HF because it is a high frequency generated by a small Tesla coil type device) is to establish an arc between the tungsten electrode and the work, without having to scratch start. Since AC current passes through zero, when welding with AC the arc stabilizer is used continuously to restart the arc 120 times per second. The danger of using the HF while stick welding is do to the fact that the HF can establish the arc through the operator! It's not the tiny current of the HF that is dangerous, it's the aperage from the welding machine that can get you. Normally open circuit voltages on welding machine do not exceed 100 volts. The electrode holder and gloves keep you from getting zapped. But if an arc is established through the operator by the HF, it can become a path for the full power of the welding machine.
BTW, if you want to use scratch start, place a small piece of copper near the weld area. Scratch the copper and carry the arc to the work area.

 

[Hawkeye]

Rick,

You are correct in that the Century unit is a pilot arc source. It will only be useful for aluminum if I use it after a suitable AC welder. Once I get it hooked up and working, I'll probably run it through my current detector to give the option of start-only operation on DC. The CD also adds post-flow timing to my Frankensystem.

I'm a bit scared to try it out in case it fries my welder.

I've used carbon for a scratch pad, but now prefer a piece of tungsten as a scratch point.

I think I'll take the same approach with welding electricity that I do at work - consciously avoid setting myself up as a path.

Cheers. Mike

 

[geotek]

I used to have one of these many years ago. I used it with a Dayton cracker-box AC welder. It did a real nice job on heavier aluminum such as 1/8 - 1/4", but because the Dayton welder had poor control on the low end, it was difficult to use with thinner material. I would not be afraid to use it with any welder, the energy generated by the HF is so low it couldn't damge anything.
Use a Tig torch with a gas valve on the torch. Turn on the gas and go. Run about 20cuft/hr gas rate, pure Argon.
For using the unit as start only, just use a foot switch to turn on and off the HF unit. You can buy foot switches that have the AC plug and outlet built into the cord like this one:
http://www.grainger.com/Grainger/LINEMASTER-Foot-Switch-2A190?Pid=search

 

[Hawkeye]

Geo,

I used to use the torch valve, but I had a lot of fun designing the current detector and post-flow timer. I'm an Electronics Engineering Technologist, among other things, so it's nice to actually use it now and then. The foot pedal (also home made) includes a switch to turn on the gas as soon as it's moved from zero. That switch could also be used to turn on the HF, but starting the welding arc can be used to shut off the HF when that option is selected.

All this is currently run on a Century 90 amp inverter, so it's the solid state components I'm concerned with. Obviously, when I get into aluminum welding, I'll be switching to an AC source of some sort. Does sine-wave AC work at all? I know square-wave AC with all the bells and whistles is best, but budget is a factor.

Thanks for the input, guys.

Mike

 

[Hawkeye]

Thanks, Rick. I've been dabbling more that delving, but I'll get there eventually. That kind of work is good in the winter, for days when I really don't feel like going anywhere.

Mike