Understanding PWM of Motor (current problem)

The one good concept presented here is that battery power ~= motor power.

Keeping that in mind; motor current is proportional to torque, and motor CEMF is proportional to motor speed. Net motor voltage is effective applied voltage (battery voltage * DF) - CEMF.

Vehicle friction losses are minor except at very low speed, typically drag dominates. Drag has v^2, v^3, and v^4 components, with the higher powers becoming dominant at higher speeds. Remember that power ~= torque * speed.

Since is real vehicles operating at lower effective voltage also means operating at a lower speed. And none of it is very linear, thanks to drag.

Operating at steady speeds, the power required goes up by a curve similar to an exponential. (In the general case, in specially designed vehicles there are speeds with atypical drag minimums.)

So at rated max speed (max power) we have effective full voltage and full current and all the power is being eaten up fighting drag.

A 1/4 decrease in power should translate to about 78% of top speed,

A 1/2 decrease in power should translate to about 60% of top speed,

More decreases result in similar arithmetic.

HTH

I seem to have gotten some of my sums wrong in my previous post, i did not pay proper attention to speed proportions and CEMF.

versus is a comparison (often numerical)

ALERT! Improper use of language!

"Versus" is a preposition.

...Jim Thompson

Dawgs, i love my pop-off chain. So handy when some d^2V/dt^2 insists on jerking it.