Measuring Torque Without Stalling Motor | Battery-Powered Solutions

[blumist]

I need to devise a way to measure the torque of a Rotating Motor. Now i already have 2 ways in mind but both of them require that the motor stops while still being powered by a battery or something. ( I think we risk permanent damage to the motor )
Can someone point me to a method that wouldnt require the stalling of a motor and still give me the torque somehow? Also, is there anyway to get torque out of the RPM value of the motor?

Thankyou!​

 

[K^2]

The torque of an electric motor depends directly on current. Relationship is pretty much linear, so once you know torque at some current, you can measure current to find torque for all other situations.

The current, in turn, depends on effective voltage across coils, which is applied voltage - back EMF voltage. The back EMF voltage depends on RPMs, and is usually also linear with these. So again, as long as you know torque at some RPM and you know applied voltage, you can figure out torque in all other situations by measuring RPMs.

Now, as far as actually measuring torque to get a reference point for either of these methods you can try one of the two things. First, you can apply a significantly lower voltage and measure torque of stalled motor. That SHOULD prevent the motor from burning out while allowing you to measure the torque, but you need to check what the maximum continuous current rating is for this motor and adjust voltage so that the current is not exceeded.

Another method is to time how long it takes for the motor to raise a weight using a simple wench. Weight * diameter of the spool = torque. Speed gives you RPM at which this torque was achieved. You can now figure out torque at any other RPM value.