[Rickertsen2]

Originally Posted by gc02

I disagree completly. I'll try and explain my theory a little better. The output of the speed controller, connected to a resistive load, gives us a nice square wave. With a square wave voltage/current are directly proportional to the duty cycle. Now if you throw an inductor in there, you no longer have a square wave, you have a funny sawtooth shaped wave and the output voltage/current are no longer linearly proportional to the duty cycle. They become related to the rise and fall times of the inductor and the length of the switching period. This non-linearity will become more pronounced at lower PWM frequiencies as the voltage/current have more time to rise and fall between the on and off switches. I'm sure you're right in that the duty cycle varies linearly, but I can definetly see how the voltage/current dont have to respond linearly.

So what you are saying is that you believe the reactance motor is varying with duty cycle? Do any of you know how to compute reactance over time of a square wave through an inductor? Would you break it up into sine waves and alanlyze the first 20 or so? Is there a simpler way? I can't even find the fourier series for anything but a truly square square wave.
BTW this is entirely possible as both tests had motors attached when they were performed. At this point we seem to have many theories and many untested hypotheses. I Think we will get a much clearer picture of what is going on onve someone measures duty cycle output vs. pwm input.