running steppers slowly

[stirling]

I have an application where I don't need fine resolution. Having done my sums it appears I'm going to be running my (200steps/rev) motors in the range 0 to 2 revs/sec so 0-400 fsps.

I understand how torque is inversly proportional to speed, but looking at the torque curves I notice that they only start at around 500 fsps - is there anything "funny" I should be aware of going on at the front of the curve i.e. when running motors slowly?

If it makes any odds I'll be using microstepping drivers.

Thanks

Ian

[Mariss Freimanis]

Yes, there is something "funny" going on. The speed-torque curve shows from 500 full-steps and higher because there are severe resonance notches (down to zero torque) in the curve from 0 RPM to 500 RPM. Otherwise torque is constant from 0 RPM up to several hundred RPM past which it drops inversely with speed. Low speeds require microstepping to get resonance-free operation and full low-speed torque.

Mariss

[stirling]

Thanks Mariss - So not a problem if I use quality microstepping drives? - got any recommendations?

Whilst you're around... Could I ask you to take a look at my last post in " I thought I knew - now I'm not so sure..." please - it's about a paragraph in the stepper guide on the gecko site.

Thanks

Ian

[Mariss Freimanis]

Please send a link to it.

Mariss

[stirling]

http://www.cnczone.com/forums/showth...632#post436632

Post #11

Thanks

Ian

[stirling]

So... The torque curves for my motor show torque starting at 500fsps to be around the 2.5Nm (354 in oz) mark. Given I'll be using a quality microstepping driver can I assume the following?

There is absolutely no point in doing "the norm" of using a Voltage several times the rated voltage. Because I'm never going to get to the speed where torque drops inversly with current.

i.e. I should use the rated voltage of my motor.

This sounds too easy (for once)

Comments appreciated.

Thanks

Ian

EDIT: Ah but of course at least one quality driver says the Voltage must be at least 4 times the rated Voltage - Other comments still appreciated though. Thanks.

[ger21]

I believe that if you try to run the motor at it's rated voltage, the torque will drop off immediately as soon as it starts to turn.

[Zappautomation]

Also the driver will have a minimum voltage that will be at lest twice the rated voltage of the motor.
Below this voltage and the driver will not start.

Originally Posted by stirling So... The torque curves for my motor show torque starting at 500fsps to be around the 2.5Nm (354 in oz) mark. Given I'll be using a quality microstepping driver can I assume the following? There is absolutely no point in doing "the norm" of using a Voltage several times the rated voltage. Because I'm never going to get to the speed where torque drops inversly with current. i.e. I should use the rated voltage of my motor. This sounds too easy (for once) Comments appreciated. Thanks Ian EDIT: Ah but of course at least one quality driver says the Voltage must be at least 4 times the rated Voltage - Other comments still appreciated though. Thanks.