Recomendation of stepper motors…

[taconite]

It seems like a trade-off:
0.9°/step --> higher resolution than 1.8°/step
0.9°/step --> lower speed where the torque drops than 1.8°/step
low inductance --> "less Back-EMF" so higher speed where the torque drops
low inductance --> motor is more expensive

[wilriker]

Another thing that I found out and cannot explain (and I hijack this thread a little but it is still related): all motors I researched, independent of all specs always have a temperature rise of 80-85°C. What does this number depend on? All they had in common was being Nema 17 but they were different lengths, different torque, different voltage, different current, different inductance, different resistance.

How can this be?

[taconite]

my suggestion:
different length = different torque
same torque but lower voltage = high current = same power (P=U*I (formula for DC))
same torque but higher voltage = low current = same power
but the temperature they have is because of what heat they can emit and this depends on the surface area --> so they have all the same emitting "factor" per length (thats why the longer motors have the same temperature)

[wilriker]

@taconite I also thought that this might be a function of power vs. length but here are two particular motors where it does not fit:

• https://www.omc-stepperonline.com/nema-17-stepper-motor/nema-17-bipolar-18deg-18ncm-255ozin-07a-29v-42x42x25mm-4-wires-17hs10-0704s.html
  Lenght: 25mm
  Power: 2.1W
• https://www.omc-stepperonline.com/nema-17-stepper-motor/nema-17-bipolar-18deg-13ncm-184ozin-1a-35v-42x42x20mm-4-wires-17hs08-1004s.html
  Length: 20mm
  Power: 3.5W

As you can see the second motor is shorter but has over 50% more power but they both have a max temperature rise of 80°C. I am clueless here. Also it is always stated that this temperature will be reached at full current in stand-still with both coils fully energized.