How to measure running torque of the Stepper motor?

LesJones

Joined Jan 8, 2017
3,495
Mount the stepper motor so the casing is free to rotate. If the motor has a shaft both ends that makes it easy. Just put a ball bearing on each shaft and support it from the ball bearings. Fix a lever to the casing of the stepper motor and connect the end of the lever to a spring balance. You will need to do something to counter balance the weight of the lever. Use thin wire and possibly coil it to reduce any restraint provided by the wire. calculate the torque from the length of the lever and reading on the spring balance. If the motor only has a shaft one end the you will have to make a mounting to support the back end of the motor on a bearing.

Les.
 

MaxHeadRoom

Joined Jul 18, 2013
23,619
I have used the pulley and spring balance method, as long as the stated winding current is maintained, the torque should be constant throughout the rpm range.
 

LesJones

Joined Jan 8, 2017
3,495
Hi Alec, When the stepper is driving a load (Either it's normal load or the load from some sort of brake.) the reaction on the stepper body will be the same as the torque on it's shaft. (Except for the friction in the ball bearings supporting the body and any force exerted by the wires to the stepping motor.) You could use a PM motor as a load and control the torque by controlling it's armature current.

Les.
 

MaxHeadRoom

Joined Jul 18, 2013
23,619
That will enable static torque to be measured. I'm not experienced with steppers, but won't the running torque be somewhat different from the static torque?
For a stepper motor, the torque will be a constant as long as the plate rated current is maintained throughout the range.
 

LowQCab

Joined Nov 6, 2012
1,096
The first bit of information that You need to provide is
WHY You need to know the Torque-Output of the Motor,
and what do You need to do with the information gathered.

Are You trying to diagnose a potential problem with a Machine ?
Do You want to compare the Outputs of 2 different Motors ?
Do You want to regulate or limit the Torque-Output ?
Do You want to illuminate an Indicator-Lamp over or under a certain Torque ?
Do You want to Record the Torque on a Chart-Recorder ?
Do You want to Compare the Torque to some other on-going Process ?
Do You want to maintain a certain RPM or Horsepower-Level ?
.
.
.
 
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