Torque vs angle in stepping motors

[patroclus]

Could anyone explain me about torque vs angle in stepping motors
for example
https://www.cs.uiowa.edu/~jones/step/physics.html
(the first image, 2.1)

I think I understand, but when I come to "Dynamics" (figure 2.6 I don't undertand "the maximun torque is at a minimun when the rotor is halfway from one step to the next"...
Halfway??

Thank you!

 

[Klaus]

Could anyone explain me about torque vs angle in stepping motors
for example
https://www.cs.uiowa.edu/~jones/step/physics.html
(the first image, 2.1)

I think I understand, but when I come to "Dynamics" (figure 2.6 I don't undertand "the maximun torque is at a minimun when the rotor is halfway from one step to the next"...
Halfway??

Thank you!

"halfway", for a 1.8 deg per step motor would mean 0.9 deg of rotor movement. The rotor moves in 'steps', if the stepping sequence is fast enough it appears as a smooth rotation.
But, one can also move the rotor in 'half' steps or even in microsteps by energising the windings in a certain way.

you would learn more from a good book on stepper motors than could be explained here in a short answer.
There is also good information on the net, have you googled for 'stepper motor principles of operation' or something like?
Klaus

 

[patroclus]

Yes, and I learned lots of things, but still don't understand why maximun avaiable torque is minimun in halfstep between one step an the next (from the graph 2.6 of above web)... I mean, I don't understand that comment about graph 2.6

 

[Klaus]

Yes, and I learned lots of things, but still don't understand why maximun avaiable torque is minimun in halfstep between one step an the next (from the graph 2.6 of above web)... I mean, I don't understand that comment about graph 2.6

You do understand that magnetic attraction (and repulsion) is strongest with the minimum air gap. Now look at the poles of the motor as being a certain distance apart. You will see that the rotor pole, when halfway between that distance, has the maximum air gap to each.

try this; on any stepper motor, short out all the leads with no power applied to it. Now try to rotate the shaft. You will find it 'cogs' from one pole to the next. The force to rotate the shaft is least when its exactly halfway between two poles (steps).
I hope this helped.
Klaus