I have to steppers with different rated current but same torque?

Both are Nema 17 with the exact same dimensions(42mm*42mm*40mm).

Stepper 1:
Rated Current: 1.2 amps
Rated Torque: 0.4 N-m

Stepper 2:
Rated Current: 1.7 amps
Rated Torque: 0.4 N-m

Does this mean that stepper 1 is as strong as stepper 2 and it's just more efficient? So Stepper 1 is just better and I should use it instead of stepper 2?

Or maybe one (or both!) of the sellers lied to you about the specs of their motor?

The 1.2A one is wound with finer wire than the 1.7A one. It will have higher resistance and inductance than the 1.7A one and will need a higher drive voltage to reach high speeds.

Edited 1 time(s). Last edit at 05/22/2017 01:21AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Would this matter if the stepper is used in the extruder knowing that the speed is quite low?

The reason I opened this topic is because when I was trying out the 1.7 amps stepper in the extruder, I got skipped steps at ~85% or lower of it's rated currently. If I set the current higher, it doesn't skip steps anymore but the stepper gets quite warm. I would guess warmer than 50 Celsius just by feel.

The 1.2 amps stepper is doing okay at 90%, but I need to do further testing.

... for your use the 1.2A-stepper would do better, as it's receiving the same torque with lower current/power, so lower heat generating ...

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Viktor
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