Stepper motor guide confusion...

Chriss

Hi *,

I try to understand which stepper motors I should pick. I read though https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors which is indeed very helpful to understand the physics but it leaves some open question here at my end.

In one part what I do not understand is the inductance. The wiki says

What this means is that if we want to achieve high speeds, we need low inductance motors and high supply voltage.

On the other hand does the docu say

Avoid motors with rated voltage (or product of rated current and phase resistance) > 4V or inductance > 4mH.

So a stepper driven at 24V with 0.6mH and 0.5Ohm is what now? OK or not?

Cheers, Chriss

Gixxerfast

@chriss AFAIK, the inductance of the motor will with increasing speed cause an increasing back EMF voltage that will counter the input voltage so that the motor at some rpm can't produce enough torque. Therefore you want to keep the motor inductance low.

Have a look in here: https://www.reprapfirmware.org/emf.html and see if the motors can give you the speed you want.

To reach higher speeds people are now starting to use 48V stepper drivers instead of 24V.

I guess someone else will be able to explain this with more accuracy

Chriss

@chriss

Yes, the emf calculator is helpful here but do not clarify that for me....

I have the idea to mod the 6HC to drive it up to 60V.

I guess I have a misunderstanding here "Avoid [...] inductance > 4mH. " Means ""Avoid more than 4mH"m doesn't it?

Cheers, Chriss

engikeneer

@chriss said in Stepper motor guide confusion...:

I guess I have a misunderstanding here "Avoid [...] inductance > 4mH. " Means ""Avoid more than 4mH"m doesn't it?

Yes that is correct. You want low inductance

Chriss

@engikeneer Thanks, I guess that I had problems in the understanding of the ">", as always. That makes clear that the two claims are logical now and point into the same direction in my head.

I guess I will give that stepper a try and see how much I can push them forward.

Cheers, Chriss

engikeneer

@chriss I was always taught that the > is a hungry crocodile so eats the bigger number

Chriss

@engikeneer said in Stepper motor guide confusion...:

@chriss I was always taught that the > is a hungry crocodile so eats the bigger number

This is what I ahve learned in school too. I have no problems with numbers, it is logical than. But in a sentence it is always a stopper for my main processing unit.

Cheers, Chriss