The 105° is class A motor Insulation witch most motor use.?
The temperature drops as pass to outside casing.?
After that I use 176°F [ 80°C] for outside case? max temperature just to be on safe side.?
Note Most could burn your had around 140°F to 145°F
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On Sun, May 5, 2024 at 10:38 AM, Tony Smith wrote:
Well it shouldn’t, but I’m not the one trying to measure it.? I don’t know what Dave thinks he’s measuring, but that 105°C he’s set as his upper limit (over boiling water temperature, by the way) is the point where the enamel on the armature coils starts failing.
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The case temperature is going to be a lot lower.? As said, if you can’t touch it it’s way too hot.
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Tony
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Why should a minilathe motor be getting extremely hot in the first place? Mine never does. These machines aren't made for heavy use and cuts should be light. On the rare occasions that I've taken heavy cuts, I use a spindle crank.
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105°C sounds rather suspiciously (or perhaps not that suspiciously) like the lower temperature limit on most magnet wire used in motor coils.
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Gets hot, the enamel melts and the coil shorts out.? If you’ve spent enough time around motors or transformers you know the smell.? That 105°C is basically the maximum temperature for the motor coils, if you let it get anywhere near that you’re asking for trouble.?
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You can get magnet wire with better heat rating, up to about 250°C, but you don’t see that much.? That’s what the class of a motor means, better insulation.? Thoe old rule of if it’s too hot to touch, it’s too hot is well worth following.
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The other reason for keeping the heat down is the magnets.? Won’t bother the typical old-school mini-lathe motors, but newer motors (eg brushless) with neodymium magnets need to be kept cool as they start losing magnetism at around 80°C.
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Tony
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After researching of motors are 221°F [105°C] after that the life is shortened.?
The outside temperature is about? 60°F to 70°F? [15 to 20°C ] less the coil temperature.? So if outside is could be wend the coil is? 221°F [105°C] the outside is between? 151°F and 161°F [85 an 90°C].
On my gauge I set the red mark at 80°C and 105°C.?
If I see gets never red it time to let motor cool down and gives little to finish the cut.?
The Capillary is attached by HVAC Aluminum tape , max temperature is 145 °C at this point the motor is toast?
Dave?
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