Can you swap electric motor thermal protection devices?
Can you swap electric motor thermal protection devices?
(OP)
Hi, all! Ok, here's my problem. I have an electric motor - a Dayton 10J152, 1/7hp - that has a one-shot thermal protection fuse in it. I hate these! So, I took an automatic reset one from another Dayton motor I have (both motors rated at 40deg C) and swapped it in place of the one-shot thermistor. I did this on a previous motor of the same model, using this same auto reset thermistor and it worked great.
With this motor, I took a little more time and ran it on my bench for awhile. It seemed to me that (1) the motor was a little louder than I'd expected and (2) it gets a lot hotter to the touch (not near the bearings but on the side) than I think it ought to be. Especially since it's under no load whatsoever. I fixed the noise by tightening the screws holding the motor together so that they were completely and evenly seated.
Am I just freaking over nothing or have I created some kind of problem by doing this? I never ran the motor with its original thermal protector, so I don't know if it was always noisy and just runs this hot normally - or is defective. It gets hot enough that it's pretty darn uncomfortable within a few minutes. Or do these auto fuses/thermistors have a certain "polarity" and maybe I have to swap the wires on it? Both the one shot and the auto have 2 contacts. On the one-shot, the ends of the fuse body were different, almost like an axial electrolytic capacitor which has a positive and negative lead. Or might it me the "B" value/curve of this this auto fuse is such that the insertion loss is significantly higher or lower than the design of the motor allows?
I'm pretty sure that the motor shouldn't get so hot unloaded. That said, I did this to the 1st, exact same model, motor because it was overheating in the hot ambient the thing has to work in in the first place and didn't want to swap one-shots all the time so maybe it's just the way these "stack" motors are? This is the same auto fuse I used in the 1st motor. It burned out some windings after about 5 months of almost continuous use, albeit in a somewhat overloaded and dusty configuration.
Thanks,
Rick
With this motor, I took a little more time and ran it on my bench for awhile. It seemed to me that (1) the motor was a little louder than I'd expected and (2) it gets a lot hotter to the touch (not near the bearings but on the side) than I think it ought to be. Especially since it's under no load whatsoever. I fixed the noise by tightening the screws holding the motor together so that they were completely and evenly seated.
Am I just freaking over nothing or have I created some kind of problem by doing this? I never ran the motor with its original thermal protector, so I don't know if it was always noisy and just runs this hot normally - or is defective. It gets hot enough that it's pretty darn uncomfortable within a few minutes. Or do these auto fuses/thermistors have a certain "polarity" and maybe I have to swap the wires on it? Both the one shot and the auto have 2 contacts. On the one-shot, the ends of the fuse body were different, almost like an axial electrolytic capacitor which has a positive and negative lead. Or might it me the "B" value/curve of this this auto fuse is such that the insertion loss is significantly higher or lower than the design of the motor allows?
I'm pretty sure that the motor shouldn't get so hot unloaded. That said, I did this to the 1st, exact same model, motor because it was overheating in the hot ambient the thing has to work in in the first place and didn't want to swap one-shots all the time so maybe it's just the way these "stack" motors are? This is the same auto fuse I used in the 1st motor. It burned out some windings after about 5 months of almost continuous use, albeit in a somewhat overloaded and dusty configuration.
Thanks,
Rick





RE: Can you swap electric motor thermal protection devices?
The thermal protective device in the motor winding has nothing to do with the motor overheating.
According to the Grainger website, a Dayton 10J152 is a shaded pole "Air Over Motor". It's a fan motor.
It requires a fan mounted on the shaft to provide adequate cooling of the device.
Hence, running the motor without proper airflow can cause it to run hotter.
John
RE: Can you swap electric motor thermal protection devices?
Given this possibility, I'd say that the problems you are having are most likely DIRECTLY related to the ambient heat; this motor is not the right type for this, unless you plan on replacing it often. The thermistor is not INTENDED to be sacraficial, it is just working out that way because even though it slows the motor down, which was SUPPOSED to take care of overloading, the ambient temperature remains too high and the current continues to be higher than design. Eventually, the weakest link fails, and that happens to be the thermistor.
You seem to have tried to circumvent the situation by replacing a PTC thermistor with a Klixon, but it may be that the motor was DESIGNED to have a certain amount of resistance in it from the thermistor, so by removing it the motor winding is getting too much voltage now and is over excited, making it vibrate more, and by the way, it will now run even HOTTER! My prediction is now a more rapid demise.
"Will work for (the memory of) salami"
RE: Can you swap electric motor thermal protection devices?
When the first 1/7hp tripped its one-shot after only 30 minutes, I added a high cfm Boxer fan to the chassis to cool the motor windings along with installing the klixon from a 1/15hp model of the same make (Dayton) and the same temp rating (40deg C). I live in Florida where it's brutally hot day and night for 335 days a year, so ambient is always high. 40C is only 104F, so with it 95+ degrees in the shade, that leaves very little margin.
The 1/7hp is the strongest I can fit into the space on this machine without very major redesign and modification. The motor is indeed turning a significantly higher load than a fan blade. It is on a vibrating lapping machine that I've modified to have a quasi-reciprocal motion using an offset shaft. It has a pulley that spins another one attached to the offset shaft. That, in turn, is inserted into a 4-bolt bearing on the bottom of a flat bottomed steel pan that is fastened atop three 2.25"x1.5" rubber shock mounts. Turning by hand, the load doesn't seem very heavy but certainly more than a fan blade. Might I lower the perceived load on the motor by using larger diameter pulleys, with the load pulley a bit smaller? I need to speed up the vibration somewhat anyway.
Thanks a TON!
Rick
RE: Can you swap electric motor thermal protection devices?
RE: Can you swap electric motor thermal protection devices?
RE: Can you swap electric motor thermal protection devices?
RE: Can you swap electric motor thermal protection devices?
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(2B)+(2B)' ?
RE: Can you swap electric motor thermal protection devices?
RE: Can you swap electric motor thermal protection devices?
http://www.devale.com/thermal-fuse/one-shot-therma...
Like I said, tiny motors for appliances is not my thing.
As to changing pulley size, that will only work if doing so somehow changes the LOAD on the motor. Pulleys just trade torque for speed, they don't chage load per se, unless the load is a centrifugal machine like a pump or fan where the Affinity Laws apply. Could be just that your 1/17th HP is too much for the load. You can often get away with higher ambient heat if you de-rate a motor, so if you cut the load an equivalent amount (since you say you can't fit anything bigger), that might work.
Or search around in something other than Grainger, their offerings are decidedly limited to very high volume movers. Try someone like Oriental Motor or Bodine and talk to a human being about what you need, I'm sure there are better choices.
Good luck.
"Will work for (the memory of) salami"
RE: Can you swap electric motor thermal protection devices?
A 1/4 hp would definitely be much better but it seems that 1/7 or 1/6hp may be the cutoff for thin, "stack" motors. Redoing the chassis for a bigger, Y48 NEMA frame size motor would require a LOT of redesign and cutting of steel or building a steel fram external to the unit for the motor. I see what y'all say about these air-over motors needing air moving thru them. Even the original 1/15hp this lap came with would shut down within 30 minutes, even at night here in FL. Once I added the fan, that problem went away. So maybe it is that running in my hands on the bench with no cooling, the motor gets hot and this is to be expected. I went ahead and installed it into the machine and it is working. It runs sometimes for over 36 hours straight before I power it down. So far, so good!
Rick