Hobart Line Voltage Input HELP!!!!

[blackfly1]

I have an OLD Hobart arc welder. There is no model number or serial number anywhere in it. I believe that it is wired for 440 AC and I need to know how to wire it for 220 AC. There is a panel inside that's says "To change line voltage refer to manual" but without model and serial number I can't get a manual.

I will describe it as best I can. I tried attaching pics, but it's not working.
It's an old Hobart AC/DC reverse 320 amp unit with a big round steering wheel type nob for the amp selection and AC/DC + - . And a small fine adjust just below and to the middle of those. Will try pics again later.


Thanks for any and all help you can be.... blackfly1:waving:

[awright]

If your machine is truly designed for only 220 or 440 volts in, it will have two primary windings, each for 220 volts. For 220 volts, they are wired in parallel (the ends of the two windings connected together and connected to the 220 volt power line via the contactor or switch. For 440 volts, the two windings are connected in series (one end of each winding connected to the incoming 440 volt line and the opposite ends of the two windings connected together.)

The ends of the windings are usually (but maybe not always on older machines) brought out to terminals on an insulated board and the changeover is made by changing the position of conductive links between terminals on the board. On a cheaper machine it is possible, but unlikely, that you relocate the wires from the windings to put the windings in series or in parallel. You will have to inspect your transformer terminations to see how they do it. The terminal board may even have information on it about how to locate the wires or links.

If it's not marked, the changeover is still easy, but you have to be very careful not to get the windings reversed. If they are wire incorrectly, they cancel each other out magnetically and appear to be a short circuit to the incoming power, which could be disasterous for your welder because then only the negligible resistance of the wires of the windings limit the current that will flow before sonething blows. Don't be afraid, just be very deliberate about identifying the winding polarity carefully BEFORE disconnecting anything! If you are not confident after inspecting the terminal board, ask for more help!

Since the machine is set up for 440 volts, you will find the windings in series, with each winding connected to the incoming power line and to the other winding. Put permanent marks or tags on the wires to identify them if they are not already identified. Disconnect the common connection of the two windings and move (physically or by means of links) the conductor of winding #1 (your arbitrary winding identification) that was previously connected to the free end of winding #2 to the line input end of winding #2. Move the conductor of winding #2 that was previously connected to the free end of winding #1 to the line input end of winding #1. Secure all connections firmly (without stripping screws, which can be a real PITA), change your power plug to be compatible with your 220 volt receptacle or wire directly into the switch box(better), and power up. If you've been careful and deliberate, things should be fine. Be sure the fan seems to be running normally. The fans are usually 220 volt fans and were wired across one winding, so they don't have to be rewired for the different supply voltages, but you should check that out. It's concievable, but very unlikely, that the fan has two windings that have to be rewired in the same fashion as the transformer.

Post pictures of the terminal board if this is not clear to you. Of course, it is always best to contact the manufacturer's tech support people to get the real scoop.

Have fun.

awright

[blackfly1]

On the panel inside the welder where the power feeds link to the windings there are four red input leads and six black winding leads. The only windings that are being fed are black #10, and black #3. Black #10 goes to the outside of the winding and black #3 goes to the inside of the winding. The only other connection in this panel crosses black 12 and black 81. Which black 12 goes to the outside of the winding and black 81 goes to the inside of the winding.
There are four seperate windings some of which connect to each other and some lead back to this panel with nothing connected to them. And where black #3 and black #10 are powered up in the panel the bar in shaped like a long "U" where if they get hot they will bend down onto a micro-switch (thermal overload protection?)
So if someone could help me figure out which terminals to attach to I should be up and welding.

Thanks a bunch.





6516

6520

6521

[awright]

First, it looks like this welder would benefit from a good blowing out with dry air from an oil-free compressor or a very well filtered oil lubricated compressor.

Second, oil lightly the fan motor.

Third, please sketch up the terminal board and show how the windings are connected to the terminal board and show the wire numbers and terminal numbers. I do not understand your description of the wiring of the terminal board and the transformer windings. Your description does not make clear the interconnections between the terminals we see in your photos and the windings. Show how the fan wires connect to the windings or terminal board.

Is the link in the middle of the terminal board connected to one end of each winding? If so, that link is probably the common point of connection between the two windings in series. If that is true, where do the other ends of the to primary windings go? Where do the incoming power wires connect to the primary windings? On the terminal board? Which terminals? Are there two links stacked where the link shows in the photos? That's a common way of storing the second link that you will need to make the parallel connection of the primary windings. If the second leink is not stacked on the visible link, is there an second link stored anywhere in the welder? If not, you will have to make a second link.

Can you show a photo of the main windings and their wires? That would help give confidence that we are, in fact, talking about the correct windings.

awright

[blackfly1]

6537

6538

6539

6540


Here are some sketches of the wiring. There are four red wires that go to the board from the contact switch (power in). There are six black wires that go from the board to the windings. Two of the black wires #10 and #3 connect from the horseshoe link to the winding. The horseshoe links these black wires to power via the red wires. The #10 wire connects to the outside of the winding. The #3 wire connects to the inside of the winding along with #5 and #81. The #10 connects to the outside of the winding along with #12 and #6.


#12 and #81 are linked together on the board and both go to the winding.
So this is what we have. Six black wires #10 and #3 power to windings, #12 and #81 linked together. #6 and #5 on the board hook to nothing along with the two red wires in between them.

I hope this helps explain my sketch. I tried to get pictures of the windings but they are in to deep with to much covering them. OH... by the way there are four windings that these six wires connect to. Some of the windings connect to each other but can't see well enough to depict how and which ones.
if this gives you enough info to tell me where to put links on the board that would be awesome. Thank you very much for your input.... blackfly1:waving:

[awright]

While we are chewing on this, why don't you print up all of the pictures of your machine (and more, if you can make them) and send them off to Hobart tech support with a request for a manual and/or instructions on how to change over the input power connections? Can't hurt. They may get intrigued that someone is still interested in operating one of their old machines. Their guess is better than mine.

What do you mean by, "#6 and #5 on the board hook to nothing along with the two red wires in between them"? Do you mean that the wires come up to the terminal board shown in attachment 6521 but that nothing is attached to them on that terminal board? That's the assumption I'm working on.

Where do the four red wires connect on the switch? I'm guessing that the red wires are connected in pairs, either on the two switch terminals or inside the switch when the switch is on. Is that true? If so, which red wires are paired? Bringing up two red wires for each incoming line may have been their way of providing for flexible connection schemes at the terminal board and allowing use of smaller , more flexible conductors between the switch and the terminal board. The four red wires may be connected to separate screw terminals on the switch, but are paired up inside the switch. Do you have a multimeter with which to test that ?

By the way, what makes you think the machine is set up for 440 volts presently? Probably is, with only one link on the terminal board, but it's worth verifying, if possible.

OK, blackfly1, here's a wild guess at how your machine is wired. It is only a guess at this point, but it can help explain why you have four lines coming from the power switch when you'd only expect two, and why there are three lines from each winding. Remember, it is only speculation at this stage, so don't rush out and move links around and apply full power without confirming my guess. Other wiring layouts are entirely possible, but the one I am speculating on makes most sense to me with the level of information presently available. We'll know more after you the resistance measurements suggested below.

I think the ends of one winding connect to #10 and #12 with a tap at #6 and the ends of the second winding connect to #3 and #81 with a tap at #5. The taps would be for 208 volt supply.

Partially verify this guess by removing the link between #12 and #81 and measuring continuity between #s 6, 10, and 12 and between #s 3, 5, and 81. There should be no continuity between the even set of wires and the odd set of wires with the link removed. (If you get continuity between some other combination of three wires, post that result.)

I think you will also find that the red wires are paired, with zero ohms between the two wires in a pair, but no continuity between the two pairs. The common wires in each pair should be found across the diagonals of the four red wired terminals on the terminal board. Remember, these are all measurements with an ohmmeter with the machine unplugged and the switch off. If you don't find the red wires connected in pairs, turn on the switch (with the machine still unplugged) and see if they then pair up.

I am tempted to carry my speculation further at this point, but in the interest of caution lets stop until you post the results of these resistance measurements.

You might as well be looking for or fabricating a link to match the one that was located between terminals 12 and 81 because you will need two links for the low voltage reconnection. Use copper strap of the cross-section of the existing link or more.

awright

[blackfly1]

Answering your ????'s
#6 and #5 go from the windings to the terminal board and don't have any jumpers.
The four red wires.... the red that is jumped to #3 is connected with the red right next to it by #5, and the red that is jumped to #10 is connected with the red right next to it by #6. So we have two red wires that go from the terminal board to the contact switch where they are crimped together and hooked to one of the hot posts at the switch, the same with the other two but connected to the other hot post at the switch.


I think that the machine is set up for 440v because it came out an an old school that some other equipment came out of that was set up for 440/480. And when I turned it on the fan seemed to be running slow on 220.
i removed the jumper between 12 and 81, tested continuity and this is what we've got.......... #10, #5 and #81 have continuity and #3, #6 and #12 have continuity and odviously #10, 5, and 81 have continuity to the red that it's jumped to and the red right next to it.
Also #12 on the terminal board has a small red wire crimped in with it that goes to the stop button on the front of the machine. Two places up from that there is a small yellow wire that all by itself hooks to the terminal board where on the sketch it says N/A (top right corner) and goes to the windings. It has a seven tag on it and has continuity to #10, 81 and 5.


Thank's for answering all of my ??'s, I feel stupid looking at this and can't figure it out, but I am a blacksmith not an electrical engineer. But I have learned ALOT from your answers. Thanks again...blackfly

[awright]

Ok, blackfly1, here's where I think we are. The general configuration is basically what I had guessed, but the terminal assignments are different from what I had assumed. Same difference.

Based upon the presence of the link between #12 and #81, I think one 220 volt winding is connected between #3 and #12 with a 208 volt tap connected to #6. A second 220 volt winding is connected between #10 and #81 with a 208 volt tap connected to #5. (It will help a LOT for you to sketch this out for yourself so you see what is happening. Then file the sketch away for future reference. It's also a good idea to keep a copy of your sketch inside the machine.)

To show the "polarity" of each of these windings, put a dot on your sketch next to the ends of the windings connected to #10 and to #12. This is the standard method of indicating winding polarity on a transformer diagram. Note that current leaving terminal #10 arrives first at the dotted end of each winding before arriving at terminal #3. This polarity must be maintained to avoid damage to your transformer.

To change to 220 volt power, remove the link between #12 and #81 and reinstall that link between terminal #12 and the adjacent terminal with the red wire. That is, you are rotating that link 90 degrees clockwise around terminal #12. Notice on your diagram that this #3-#12 winding is now connected directly across the incoming power line, as it should be.

Now add the link that you made last night between terminal #81 and the adjacent terminal with the red wire, putting that winding directly across the incoming power line and in PARALLEL with the other winding. Notice that the dotted end of each winding is now connected to the power line that is connected to the bimetal "U" link connected to terminal #10, showing that proper winding polarity has been maintained through the switchover.

IF you had 208 volt supply, I think you would have connected one of the links between terminal #6 and the nearest red wire and the other link between terminal #5 and the nearest red wire (i.e., both in line). This is an assumption that you should check out very quickly when you first power up the machine on 220 volts to be sure that our other assumptions are correct. To check this out, clip your voltmeter test leads to terminals #3 and #6 BEFORE powering up the machine initially after reconnecting the terminals for 220 volts. Turn on the machine, very quickly read the voltage, and immediately turn off the machine. Hopefully you will have read about 208 volts. Do the same with your test leads clipped to terminals #10 and #5. If you did not read about 208 volts, we should discuss it further BEFORE you leave the machine on for more than a few seconds.

If you get a 208 volt reading above, turn the machine on with the covers open and listen, watch, and smell for anything amiss while poised to turn it off quickly without having to grope for the switch or think in case anything doesn't seem right. If you don't get any smoke or signs of hot wires and you don't smell anything or hear any strange noises except normal hum and fan noise, you are probably set to go. Observe that the fan seems to be running normally, then run a bead!

I am guessing that the red wire you see running from terminal #12 to the "STOP" switch on the front panel is part of the loop that holds the main contactor on. The red pushbutton switch is probably normally closed. True? When you push the red button, the current holding the contactor closed is interrupted, dropping the contactor out. This is a typical method of controlling a contactor energized machine.

I still urge you to blow out the machine with clean, dry air and put only a drop or two of oil on the fan bearings (assuming sleeve bearings) before powering up the machine.

Be sure to let us know how things turn out.

Have fun.

awright

P. S. Remember that I am a hobbyist interested in electronics, not an electrical engineer and not a welder serviceman. I assume no responsibility for anything that happens. Remember also to connect your test leads to the machine only when it is turned off or disconnected from the line. Don't grope around inside the energized machine.