stepper motor not delivering expected torque.

Mar 07, 2005 3 Replies
N

Hello,



We have a NEMA-23 a stepper motor from there:

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270 oz/in Model # RHT23-270 rated at 2.48 V and 4 amps.

and we are using a stepper driver FT-3 from there:



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the FT-3 driver works for unipolar motor, so I am really expecting



1.35 Nm (190 oz-in) torque for the motor mentionned above. Yet, when we implement this solution ( a power supply of 5 V and resistors of .6 Ohms), we barely get 1/10th of that torque. What are we doing wrong ?

Jake.



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D

A couple of points.

  1. A stepper motors torque is rated while it is stopped. The faster it turns the less torque it has because the coils can't charge fast enough.
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N

Dan, Thank you,

I understand for the torque curve showing a decreasing slope, so that indeed when it turns, the motor cannot have the max holding torque. Yet, we are talking about relatively slow speed. Irrespective I see you point.

Now to the second one, what do you mean we need to ballast resistors: increase resistor size ? If so I can show my calculation so that everybody can get a lesson out of our initiation in this realm :-)

Jake.

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R

Do you have a current reading from your powersupply? Lots of supplies have current limits. Be sure you're really getting 5V at 4A before jumping to conclusions.

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