Hello all,(adsbygoogle = window.adsbygoogle || []).push({});

I hope you can fill a couple of holes in my understanding. As part of a school assignment I have investigated the relationship between torque and current in a DC motor. I have used linear regression and the linear fit is pretty good. I have done research on the relationship between voltage and speed, and current and torque. Both relationships, according to my sources, are linear. In addition to this, a quick google image search on DC current/torque curves yields many line graphs.

Can anyone point me to why this relationship exists? I realize that looking at all the relevant formulas like V=IR, torque=BAINcostheta, F=BILsintheta.... there are no powers and the angles aren't really considered a variable. This points to a linear relationship between torque and current.

But what I really want to know is like the principles behind this. Is there something in the motor principle I might not have spotted??

Also, I have grounded my regression line to the origin of the graph using excel. I don't think this accounts for no-load torque. I guess what I am asking here is whether there is still torque at a negligible current.

If this is in the wrong section I am sorry. I don't really think this is homework (it's more of a major assessment item) and I merely seek advice. I know what it's like to have newcomers post in wrong forums (I normally hang around the saxophone forum!) :)

Thanks a lot for any help!

JH

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# Torque vs Current of a DC motor

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