Stepper motor not moving at certain harmonics?

stepper motor not moving

Hi guys, i'm trying to drive a stepper (half-step) at a rather high frequency (8kHz) by ramping it up.

I was told under load, there are certain 'harmonics' or frequency range which the stepper would just stall and refuse to drive.

Is this true? Can someone explain the theory behind it? And how can i find this range of frequencies to avoid?

I tried googling for it but i'm getting inrelevant results (i think harmonics is not the right keyword).

Many thanks in advance!

stepper motor substitute

it should not happen. There is something wrong with your circuit.

stepper motor ramp

Hello,

may be it could happen under particular circumstances with resonant load, but it's surely not a general stepper motor problem. Or do you mean, someone experienced this behaviour with your specific hardware?

First thing would be to assure, that the motor is actually operated within it's specifications, also regarding the applied load. If not, it would probably always loose "lock" at the same frequency.

As suggested, it also should be assured, that the driver is sourcing (almost) constant current at the said frequency and driving wave pattern is correct.

Regards,
Frank

+stall behaviour stepper

last time I did some stepper motor projects... and and i am not a theory guy. so my explanation might not be correct...

if I pulse it too fast (high freq), then the stepper motor will not run, what i can think of is that the motor magnectic coil isn't fully functional, another coil field is started, so the motor cannot run...

why a stepper motor stalls at high frequencies

after each step motor required some time to take mechanical action after all it is mechanical device !

and before landing to correct position , if signal is applied to move further , i think at this movement motor(int assembly) is not in correct position to cause an effect !

so , these could be happen !

stepper motor tops out at certain frequency

The same piece of hardware is used for other stepper motors and they are working fine. The only difference is the driving freq and the load. For this application my target freq is rather high.

If i take away the load, the motor can achieve my target freq without any issues. But if i apply the load, it stalls somewhere in between while it's ramping up. That's why i was wondering if resonance could be an issue.

you always ramp within a ramp with motors

not just straight up
take it in stages of ramp to allow as other point out the latent hysterisis of motors and momentum etc to allow the new stable state

when each state is reached {using sensors } the software issues a speed ramp of a little then checks to see conformance

it is the conformance and ramp too it most machines use

things like washing machines etc use this ramping on sense system to drive pwm to ac motors via triacs checking things like load disrtibution pump out water is ongoing heat isnt too much how many rinses to go what spin speed as a max on this spin cycle etc

stable stages depend on load stress planed for and mechanics like th eframe the motor sits in drum speed etc etc max load etc.....and more these days efficiency steps like if no more water comes out ramp down pump less etc ,,,, energy savings


so...

there are many kinds of stepper motor also

ac motors use a pickup coil and ramp synromech with the motor speed
the faster it goes the higher the frequncy in sync sync broken = apply power again
till sync most older washing machines use these rotor coils

Most steppers will resonate at some frequency and stall as you described.
Do you have a different motor you could substitute easily?
Some brands have better/different performance in that area.
I found this out when building a CNC router. My "Y" axis would stall above ~24 IPM
with my original motor. I replaced it with another motor and can now run at ~40 IPM.
No other changes were made. I don't remember the brands involved. Not at the shop.

Good luck on your project