I am just curious how some steppers of the same torque can have drastically different power needs?

I have 3 steppers sitting in front of me right now... all three are right around 1200in/oz one is rated for 7amp, another 3amp, and yet another at 5amp.

I was told that it is really voltage that matters to these guys. the more volts you shoot at them in a pulse the more torque you get.

one guy i talked to told me that the amperage requirements are really nothing more than an indication of efficeincy. he said that older motors needed more current to do the same work. due to better stronger magnets, and better design, you can now do the same amount of work with less juice. i asked if i would gain anything going with a higher amp stepper... and he said no, i was just getting something less effiecient and would have to spend more money on larger power suppies and all. I am not sure i believe all that... it appears that manufacturers still make steppers in various currents... so why would they bother making a 9amp when they can do the same thing with a 3amp? there has to be something different between different amp rated motors. is one faster? one cheaper? one last longer?

and then what happens if you under or overpower a stepper current wise? say i put a 9amp motor on a driver that supports only 7amp... or if i accidentally put a 3amp stepper on a driver set to 9 amps? will i burn out one of the components? will i just loose or gain power?

I was just hoping someone could explain the effects of voltage and amperage on a stepper to me... just trying to understand this a little better.

I have one driver that needs external power... it says up to 36v... and outputs up to 3amp per stepper.

i have another driver that is self contained, and you plug it in to 110v, and it outputs up to 7amp.... but never tells you voltage output anywhere.

I dont have anything rated for 9amps, so i am afraid i will be unable to power my one stepper... i could use the 7amp driver... but i dont want to risk anything... like will i fry the driver if it is trying to power a 9amp stepper?

what cases would you want or need a higher amp stepper?



also... is ther a way to improve the speed of a stepper? i bought three 1200in/oz 3.0amp steppers to use on my X Y and Z... and was thrilled with the power they had, but man are they dog slow. the guy who sold them to me told me that is the trade off... smaller ones are faster but less powerful... and the bigger ones are all slow.