Scaling

[KenWittlief]

Originally Posted by Joe Ross

The following thread goes into a lot about why the graph looks like that. http://www.chiefdelphi.com/forums/sh...tor+non-linear

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Joe - you are cruel! I read through all 5 pages of that thread from last year, and my head is still spinning :^O

I think I can summarize and answer TimCraigs statement concerning the linearity of the Victors:

1. The Victors output a constant 12VDC that is pulse width modulated. The frequency of this variable duty cycle square wave is 120Hz.

2. You cannot measure the DC equivalent voltage level with a standard DMM or analog voltmeter - you need a true RMS meter (like a Fluke 87). Many people who experiment with free energy motors and generators fall into this trap - they created PWM square wave power circuits and then measure the voltage with a standard (averaging) DMM, and think they have invented perpetual motion. Average voltage is only equal to RMS voltage with a perfect sine wave. For anything else you need a true RMS meter.

3. The speed of the motor is dependant on several factors, including the load. If you measure input command against motor speed, you will get very different results if the motor is unloaded or fully loaded (to its spec'd HP output). Part of the reason is the 12V square wave PWM drive from the victor. The short pulse acts like its kicking the armature for a fraction of a millisecond at low output values. If the motor is not loaded that short kick gives it enough inertia to keep spinning until the next kick (8mS later).

So the bottom line is: if you want to measure output voltage of the Victor you need a true RMS meter, and if you want to plot Victor PWM input against motor speed, the motor must be fully loaded to get the most accurate result.

The duty cycle, and therefore the RMS output of the Victors is linear with the input PWM values. The thing you are really controlling when you vary the PWM command to the Victor is not the speed of the motor, you are controlling its torque (rotational force). The resulting speed from that torque depends on the load.