Repair of 220v welder fan motor

[Raspy]

Not to be glib, but for $20 I could just wire a 110 fan to a single hot leg and the ground. What's the advantage of the transformer?

Most buzz box welders, and I think yours does too, have no neutral wire. The ground wire is not a current carrying wire. It's there for safety only.

 

[dex3361]

I would stick with a 240V fan and here are a few that would work the cheapest to the most expensive. Keep in mind that 500CFM is a lot of air I would likely order 2 of the cheapest unit and try 1 and if that not enough install the 2nd cheap fan. These fans often run continuous for years.
Surplus Center - 112 CFM 220 VAC FAN
Surplus Center - 500 CFM 230 VAC 10" FAN
Surplus Center - 500 CFM 230 VAC HOWARD FAN W/GUARD

 

[Travelover]

I'd use a pancake fan, which can be purchased very cheaply on line or off eBay. If you can't find a 220 volt fan easily, you can just wire two 110 volt fans in series. It might even be cheaper and work better.

140MM Fans, 140MM Cooling Fans, 140MM Case Fans at TigerDirect.com

 

[Raspy]

I would stick with a 240V fan and here are a few that would work the cheapest to the most expensive. Keep in mind that 500CFM is a lot of air I would likely order 2 of the cheapest unit and try 1 and if that not enough install the 2nd cheap fan. These fans often run continuous for years.
Surplus Center - 112 CFM 220 VAC FAN

This is the one I'd pick. One would be fine, but two wouldn't hurt. I simply mounted mine on a very simple bracket near the bottom of the box, pointing straight up toward the transformer.

Also, see if they offer the cords for these. Some models, and I think this one in particular, have prongs built in to accept a standard plug. But you can also solder wires on if needed, that's what I did.

Definitely go with a muffin fan. They seem to last forever and are usually pretty quiet for what they do.

Also, as mentioned, you could wire two in series, but just get one 220 volt fan and be done with it.

 

[joshuabardwell]

This is the one I'd pick. Also, as mentioned, you could wire two in series, but just get one 220 volt fan and be done with it.

Wow! That fan is even cheaper, with higher CFM, than the one I found on Amazon. What a deal! I have also read about people wiring them to the service side of the main power switch, so that the fans continue to run (and cool) after the unit is switched off. That's a thought. I agree that there's no point in wiring 110 fans in series, although it's a very clever idea and I will keep it in my back pocket for future use. They seem to be basically the same price as the 220 ones.

Now, the real question is why the manufacturer used that fancy-schmancy (expensive) fan motor when these little things seem to be better in every way and cheaper.

 

[EE_Bota]

Your video seems to show stiction as it stops, and as you restart it, so I don't think it is electrical. I'd lube it up, and see how it does.

 

[joshuabardwell]

Thanks for the input, everybody! I am going to go ahead and get the fan that was suggested by Dex. It will run me $20 including shipping, and I don't think I'm going to come away better than that.

I would still be interested if anybody could answer my question about the expected resistance between the leads of the motor. Just to recap, I measure 33 ohms between the two leads of the motor. What is the expected value for a correctly operating motor? Basically, should it be "some resistance" because of the length of the winding, or should it be very low resistance--basically a short? My understanding is that an "open" between the leads indicates a break in the winding, but I don't know what to make of the ohm reading I'm getting.

 

[joshuabardwell]

Your video seems to show stiction as it stops, and as you restart it, so I don't think it is electrical. I'd lube it up, and see how it does.

I have squirted some silicon lubricant into it, as well as disassembling it and looking for sticking or rubbing parts. Also, it spins quite freely when the power is off. It's only when it's powered on that it acts like that.

 

[Raspy]

Wow! That fan is even cheaper, with higher CFM, than the one I found on Amazon. What a deal! I have also read about people wiring them to the service side of the main power switch, so that the fans continue to run (and cool) after the unit is switched off. That's a thought. I agree that there's no point in wiring 110 fans in series, although it's a very clever idea and I will keep it in my back pocket for future use. They seem to be basically the same price as the 220 ones.

Now, the real question is why the manufacturer used that fancy-schmancy (expensive) fan motor when these little things seem to be better in every way and cheaper.

The fan motor that came in your welder cost the manufacturer less than a muffin fan. That's that answer. They probably paid about 50 cents for it and probably buy them buy the barrel full. The C-Frame motor is the cheapest kind of fan motor.

The oilite bearings eventually dry out and wear out or get contaminated with dust. Those motors have very little starting torque. Then the armature comes in contact with the surrounding iron poles and they cannot run. This can be after they are warm up but not quite when they are cool. Mine got to where it would not start. Oiling and cleaning only helped a little and only temporarily.

It might be fun to analyze it further, but tossing it and getting a superior one to replace it is the best solution.

The ohm reading will depend on the motor HP so it's hard to say what it should be on yours. Yours is not an open circuit and it can't be shorted either, it's a bearing problem. Just toss it.

 

[EE_Bota]

I have squirted some silicon lubricant into it, as well as disassembling it and looking for sticking or rubbing parts. Also, it spins quite freely when the power is off. It's only when it's powered on that it acts like that.

Hmmm...that's interesting. I could not think of an electrical failure mode to do what you described, so I started searching on the internet looking for failure modes that would cause the rotor to "stick." I was not able to find any. It sounds like braking but I don't see how that can be enacted in the scenario described. Good luck with it.