Trying to understand a motors speed - torque curves

Thread Starter

mikeoz

Joined Sep 25, 2017
86
Hi,

I'm trying to understand the motor curves for a particular 12VDC gear motor, Link here: https://www.robotshop.com/media/files/pdf2/016-rb-cyt-34.pdf
I only need the motor to run at slow speeds (4 or 5 RPM). Reading the top graph on the page, at 5 RPM it says the motor will produce (roughly) 750 oz-in of torque. Is this the maximum torque the motor can produce at that RPM (before it slows down)?

Also, am I reading the top graph correctly when I say at that speed of 5 RPM the motor is drawing 3000mA?

Any help would be greatly appreciated.

Thanks

Michael
 

AlbertHall

Joined Jun 4, 2014
12,345
All those specs assume the motor is being supplied with its rated voltage - 12V.
You could get it to run at 5RPM either by applying 12V and a torque of about 750 oz.ins (from the torque/power graph) and if you do that the motor will draw about 3000mA as you say.
Or you could apply a lower voltage and a lower torque but the spec is silent on the motor performance at other voltages.
 

Thread Starter

mikeoz

Joined Sep 25, 2017
86
Thanks Albert.
So I can expect roughly 750 oz-in of torque at 5 RPM as i'll be running the motor at 12v from an SLA battery and controlling the speed with PWM.

Does the efficency curve on the same page suggest that at this speed it's not a very efficient use of that motor?

Thanks again,

Michael
 

AlbertHall

Joined Jun 4, 2014
12,345
Certainly the efficiency in terms of power out divided by power in will less than the motor could achieve but if it does the job then all is well.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
That looks a poor performance compared to the DC motor I have used in the past, where Continuous torque is maximum at zero rpm and fairly flat up to rated rpm.
Motor curves usually display continuous torque (current) and intermittent torque curves.
Max.
 

Thread Starter

mikeoz

Joined Sep 25, 2017
86
I agree Albert, the motor curves are a big help.
Thanks for the replies everyone, I'll look into a suitable driver for it.

Michael
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
If it has a high ratio G.B. it is going to stop fairly quickly already due to the friction/inertia etc.
Max.
 
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