Speed/Torque Curve Orientation 1

[Brad1979]

I've seen speed/torque curves for motors that have torque on the x-axis and others that have it on the y-axis. Does anybody know of any reasons why people do this one way or the other? Or is it just personal preference. The only thing I can think of is if you go by the convention of putting independent variables on the x-axis, then torque should probably go on the x-axis.

 

[DRWeig]

Mathematically, you stated the answer. Normal expression is y=f(x). So if you're plotting speed as a function of torque, then torque goes on the x-axis. If you're plotting torque as a function of speed, then torque goes on the y-axis.


Best to you,

Goober Dave

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[jraef]

I've just assumed it's a personal preference, but the X-Y issue makes sense now that you mention it. So it may be related to whether they call it a "Torque/Speed Curve" or a "Speed/Torque Curve" then huh? I'll have to look for that next time I look at one.

"Will work for (the memory of) salami"

 

[electricpete]

There is only one torque value for any given speed.
There can be two speed values for a given torque.
So to me it makes more sense to consider speed as independent variable.

But in the end, personal preference is all that it is.
I'm reasonably sure there is no standard (and I'm not saying there should be either...it's a pretty minor format detail after all).

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(2B)+(2B)' ?

 

[mikekilroy]

I remember and still have a lot of Hugo Unruh's original Inland Motor torque motor speed torque curves" from the late 1950's, early 1960's time frame. Historically torque was X and speed Y axis on these first high performance torque motors. This stayed the norm for torque motors and then servo motors through to about 2005.

Meanwhile, speed torque curves for AC induction motors typically had speed or freq as X so torque or amps Y.

IIRC around 2005 a few BLDC and AC servo motor manufactures, IMO, in an attempt to differentiate themselves from their competitors, began swapping torque to Y axis. It seemed to gain moment for a few years but seems to have come back around to the normal torque on X for servos, and always speed on X for induction motors.

Sorta like the phone number format rage for a while of 937.696.227x vs more normal (937) 696-227x. Or bell bottom jeans.

 

[DRWeig]

Bell bottoms, Mike? With a leisure suit I hope.

I looked at a few different curves, all had speed on the x-axis which confims electricpete's comment. I have seen one the other way around though, just can't find it quickly.

Best to you,

Goober Dave

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[iop995]

In most design process you know load and speed requirments, so load torque is an input (X axis) and need to see what speed will develop your choosed motor (on Y axis). These verification may be done for entire load torque range. Speed is a resultant from motor torque, load torque and other involved factors, not an input. So, normal figure is torque on X and speed on Y. Reversed may be usefull in motor - integrated VFD with vectorial or similar control law, where need to know developed torque for various frequency (speed).

 

[LionelHutz]

3-phase induction motor models use slip to calculate torque and current. If you measured the motor torque and current characteristics, you would hold different speeds and measure the torque and current. So, it would make sense to use slip or speed as the independent variable or X axis.