Motion Control and Motor Drives

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stepper motor drive - heat - how to put them in a mode to limit the heat dissipation from the drive ?

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I'm using a system using a PXIe with 2 stepper motors NEMA34-6, driven by SMD-7621 drives.

The system requires to be powered-up 24/24 hours 7/7days.

Most of the time, the motor does not need to move ... 

It seems that the motor remains in some sort of "active" brake mode, and the drive constantly dissipate heat, even if no movement is required.

I measured the steady state temperature of the drive, which is about 50°C, measured on the aluminum heat sink.

Is it safe to have the drive constantly at this temperature, 24/24, 7/7 ?


Is there a way to switch the drive into some kind of sleep mode, when no movement is required by the control ? Would such mode, if it exist, decrease the temperature from the drive ?


I control the system using Labview, on a PXIe using a NI-73xx board, so such mode should be controlled via the Labivew code, in which I could detect situations when I will not need to move the motor anymore .... 


Any help on this subject will be greatly appreciated.






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Message 1 of 6

Hi JFBerlemont,


I don't know of any sleep mode like what you are describing, but 50" C seems well within operating specifications.

Julian R.
Applications Engineer
National Instruments
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Message 2 of 6

Almost all stepper drives have an idle current reduction function.  When the drive stops seeing steps after a certain amount of time, the current is reduced.  Not familiar with this drive, but it does have this function, and it can be set using the configuration software.

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Message 3 of 6

Thanks all for the answers.


I looked into the drive configuration utility, and I suppose that what you are suggesting is to change the Idle Current % (see attached screenprint), down to 10 or 20%, so that it will decrease a bit the losses in the drive itself ... Shouldn't it ? So far, I did not change anything to the drive settings, as I had selected a standard ST34-6 stepper motor from NI, but I will give a try to this and see if it reduces the temperature of the drive.


For my information, do you think that it is reasonable to bring the idle current to zero, somehow disabling the control in idle mode ? I do not need a "brake" function as the stepper motor is linked to a mechanically self locking device, basically, a 100:1 reductor linked to a ball screw.


Thanks for the advices.




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Message 4 of 6
Accepted by topic author JFBerlemont
08-27-2015 04:09 PM

Yes, that is the parameter you should change.  That drive is actually an Applied Motion Productss drive.  I am not sure how critical it is to keep your position.  It is possible to lose a little position if you go all the way down to 0%.  For example, if you are using microstepping, and you reduce the current to 0, then the motor might jump to the next full step.

Message 5 of 6

I have never heard of any stepper motor driver with an idle current reduction down to zero. Usually the current is reduced to 20 ... 50 p.c. of the normal current.. Some drivers have a disable line which cuts off the current completely, but - as already mentioned - in this case the drive will return to a full step position after enabling it again.

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Message 6 of 6