SA 200 Question

Date 04-02-2008 03:12

That '81 should have as much copper as any of 'em, acording to K Sellon, this forum's expert on SA 200's.

The questions You need to ask Yourself are: 1) Do I need the Aux. power from that Bobcat? 2) Do I need CV output? 3) Do I need AC output?

I think it really depends what kind of work You do. For pipeline work You would want the SA 200 hands down.

By 52lincoln (***)

Date 04-02-2008 04:09

i think peaple harpe on that all copper deal to much.so what if you have to crank it up a lil towards the end of the day.they are made to run hard.my 2 cents

By KSellon (****)

Date 04-04-2008 13:15

*****applause***** Thank you 52.

So many myths so little time. What are you doing with the machine? Do you need an industrial engine or do you need auxillary power?

By Sberry

Date 04-04-2008 15:45

Doesn't sound like a guy putting 8 hrs on a machine needs a specialists unit, one of the main reason for the smaller machine is the AC power.

By DONKEY PUNCH Date 04-05-2008 00:04

not to come off like a prick but if u don't know if its a good trade for u then u probly don't need or use either one . what are u doing with it ?

By okwelder82 (***)

Date 04-06-2008 21:16

Well I got a good deal on the Bobcat 250 and I put a rig together and am trying to break into rig welding. I have a couple friends that are rig welders and they said I could get started with a bobcat on just about everything but pipeline but if Im wanting to pipeline I will need a liquid cooled machine such as an SA200. I came on here looking for insite on the deal seeing how I have seen older SA200's for $2000 or less an I could sell The bobcat right now for $3000. The guy was wanting to trade strait across and I wasnt sure if it was a good deal or not. The fact that I only have 8 hrs on the bobcat just means that its a pretty new machine and Im not rig welding yet. The only thing I have really used it for was taking my 6G cert test. Well just wanted to give everyone a little more info about my post.

By 357max

Date 04-06-2008 21:43

The Bobcat has a great single phase arc. The 200 has a three phase arc. The Trailblazer has a three phase arc.

By DaveBoyer (*****)

Date 04-07-2008 04:20

Not to be a prick, but the SA200 is a generator, and has a true DC output [a generator makes DC as oposed to an alternator, like the others have, which is rectified to DC].

By 357max

Date 04-07-2008 15:59

Question, how does electricity happen, ie what factors are necessary to produce electricity? Three factors; a magnetic field, a current carrying conductor and motion between the magnetic field and the conductor. Therefore the magnet may move or the conductor moves. Observing what happens with an oscilloscope the alternating current sine wave shows a building to a maximum positive value and then to a maximum negative value.
A generator produces alternating current with a rotating conductor and a stationary magnetic field. The generator rectifies the alternating current with the commutator. This happens when the current is picked off the rotating commutator with the carbon brush. It picks off one half of the alternating current sine wave ie producing direct current.
The alternator produces alternating current by rotating the magnets with stationary conductors. The alternator's brushes put a small amount of exciting voltage through the brush to the rotating slip rings. The weld current is picked off the stator (stationary conductor). Not a rotating shaft like the generator. The alternator rectifies the alternating current with the rectifier, an electrical device. Alternators may be single or three phase and generators are three phase.
An interesting phenomenon about generators is when voltage is applied to the output terminals the generator becomes a direct current electric motor. The alternator's rectifier blocks the reverse electrical flow.

By gshuma

Date 04-07-2008 18:40

I have always wanted to look at the output of an SA200 with a 'scope and see how "bumpy" that wave form was.
ALL generated or rectified DC is pulsating or bumpy as seen on a 'scope. The output is cleaned up by use of coils, sometimes called chokes, and sometimes also capacitors.
If you throw a 'scope on a expensive electronic power supply you will still not see a flat waveform like a battery.
I had a 300/300 TIG that ran very smothly, out of curiosity one of the guys 'scoped it and we were very suprised at how bad (to us) the output looked.

Now that I'm thinking about it I'll have to find an inverter welder and look at that.

By DaveBoyer (*****)

Date 04-08-2008 03:08

357, You are correct up to the point where You say that generators are 3 phase. Clearly they are not, this should be obvious to You by the number of bars on the comutator. The output is DC, does not have phases, and has much less ripple amplitude than a rectified 3 phase sine wave. There will be many many more ripples however. An alternator can be any number of phases, it all depends on how it is wound. Presently 1 and 3 phase are the commonly used ones, there used to be 2 phase power in some areas, if You were winding Your own alternator You could have as many phases as You want.

By 357max

Date 04-08-2008 14:37

You are right. The three phase would be the input power to operate a motor generator. The large number of coils on the armature would act "like" a three phase arc. Since selling my SA-200 and sending its owner's manual to its new owner; I don't have the schematic which describes how many coils are on the armature. It is a bunch. For discussion, how many are there?
One coil would appear as a single phase weld output. 4-coils wound 90 degrees from each other would smooth the "ripples". And, increasing the number of coils would make it even smoother.
For discussion; the Miller Trailblazer alternator design should also have a very smooth arc with three phase coils and 4 magnetic poles. It spins at 3600 rpm producing 120 hertz ac weld output per single phase. With 3 single phases this should be 360 hertz. And then rectifying it should double the frequency of ripple to 720 hertz DC. If my electrical theory serves me correctly.

By DaveBoyer (*****)

Date 04-08-2008 21:09

357, the great number of poles on the generator makes the output smoother than a 3 phase, I don't know how many poles are on an SA200, but my old Hobart has a bunch. Aditionally, the comutator is only conecting the peaks of the wave forms. While this would be to "noisy" for an audio circut, it is a darn smooth welding output.

With regard to the 3600 RPM 4 pole 3 phase Trailblazer You have calculated the ripple frequency properly. The output would be correctly refered to as 120 Hz 3 phase, as the frequency is counted based on a full cycle of one phase, just as line power is specified.

I would have liked to have one of those Trailblazers, but I ended up with a Ranger 9 instead.

By 357max

Date 04-08-2008 21:20

The Trailblazer and the newer Legends made by Miller are the only three phase weld output machines in the 500 pound class. I have the ac/dc Trailblazer. Next one I buy will be the 275 with dc only. When I need ac I use the Dynasty 200 plugged into the Trailblazer.

By DaveBoyer (*****)

Date 04-09-2008 02:45

I know My Ranger 9 isn't in that class with it's single phase arc and not having a seperate alternator for Aux power. I got this machine mostly for standby power at home, and figured while I was shelling out for a generator, it may as well be a multi process welder as well. I havn't actually used it for anything yet, but the machine to house cable is made and ready. I run it monthly with some Aux. load to keep it in ready condition.