Current curve analysis for DC motor stall problem 3

[Saramacow]

Hello,

I want to perform a root cause analysis to know why a DC motor is stalling.

The characteristics of the motor can be found here:

https://nl.aliexpress.com/item/3296...2eqMBRQcnU-WcmKRrc4aAmJiEALw_wcB&gclsrc=aw.ds

Photo of the motor:

https://files.engineering.com/getfi...90-ec35-4837-afde-2a9653f06438&file=motor.JPG

The motor is intended to move a sequence of plastic gears and cams.

For now I'm looking at the current curves from the endurance tests performed, and I find graphs like the attached ones.

https://files.engineering.com/getfi...c-6ad1-4b45-b7da-6c401ba962f1&file=Graph1.JPG

https://files.engineering.com/getfi...c-d9b3-450a-b003-2e7e573e214c&file=Graph2.JPG

https://files.engineering.com/getfi...5-1f85-4b14-8ae1-baa33b496278&file=Graph3.JPG

AT some point it starts stalling (no movement, high current) and looking at the graphs I think it-s not the motor itself but something that the motor finds on its way so it gets stalled.

I wonder what other information can we extract from these curves? Any idea? I wonder if the curves give any information about the possible root cause of this problem.

Many thanks in advance!

 

[dArsonval]

Any electric motor has two battles to confront. (Not including environment.)

The potential required for it to function, and the load it's being asked to drive.

If the motor is stalling, the cause is excessive load at that "...some point..."

The motor didn't do it. The load did.

John

 

[Saramacow]

Thanks for your reply!

And when starting the root analysis, any idea on what to start with?

maybe a torque analysis, or failure tree directly, I'm wondering how to start the trouble shooting.

 

[itsmoked]

Remove the motor and replace it with a tiny crank.
Turn the crank with your fingers. You will learn a whole bunch about the load.

Next find the hardest point in the load cycle with your fingers. Stop just before it.

Tie thread to the arm of the lever and use some accurate way to measure the force required to pull the lever thru the largest load. The thread must be pulled exactly perpendicular to the crank arm. This could be via small pulleys and small adjustable weights like dimes dropped in a cup or a small spring-scale, whatever. Once you qualitatively measure the force you multiply it by the crank handle length. This equals the torque required to be provided by the motor to make the same thing occur. Multiply this by 2 or 3 to give what the motor/power-system should be able to supply to reliably operate the system.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[7anoter4]

I think-according to Graph2-the motor attaints the rated current in 600 msec but the load decrease to 1/2 of rated and after 3.5 second the load rises to 3
times the rated for about 1150 msec and stops.

 

[waross]

US $1.89 and it stalls? Forget it. Buy a bigger motor for about $5.00
When you overload it, it stalls.
or
It stalls when you overload it.
Either way, don't waste our time on a $2 toy.
But first, follow itsmoked's suggestion and check for binding in your gear train.
I once had to replace a $2.00 motor with a $14.00 motor.
Stuff happens.

Bill
--------------------
"Why not the best?"
Jimmy Carter