[MPaulHolmes]

I read that hilarious story from Lee before starting this controller! Isn't Lee awesome!

Yes, you got it Bill. It has hardware and software current limiting. The hardware current limiting disables the mosfet driver in like 2-3 microseconds or so, and then the software doesn't just turn the mosfets on at the end of the cycle (which is what Curtis did! BOZOS! hahaha!!! Stop that, Paul.).

If you check out Lee's explanation, with the higher frequency, the time was too short (because of the inductance in the motor) to allow the current to decay much at all. So, when the curtis turned the mosfets on right after a SINGLE CYCLE, the current hadn't really fallen, and then it would continue to rise, then FIRE FIRE FIRE! So, they slowed down the frequency to give the current a chance to fall, because they wanted to wait for a single cycle for some weird reason before turning them on again.

Maybe I'm missing something, but in my software, I just wait until I hear back from the A/D channel that reads current that the current has fallen below 500 amps. Then I wait another couple cycles, just for gravy, and then I re-enable the mosfet driver. You can barely feel when the hardware current limiting kicks in. It feels like a very very faint loss of power (from the average of the delays and the 500amps). It's hard to get to the current limit. You have to be at low RPM and on a hill, and that's with my crappy control software. I'm done with the PI loop, but I haven't tested it yet to find the optimum P and I. Then, according to Fran (on EVTech) it will be unlikely that I will ever run into the hardware current limiting again, because the software current limiting on a well tuned PI loop is very good.

Another thing to note is that Curtis (maybe still does???) had throttle proportional to PWM duty, and not current!!! So, it would have very high current at low throttle, which is why the curtises would jerk when starting out, and why they had trouble with current limiting at low RPM. I know my curtis does. And I know the home-made one takes off as gentle as a feather dropping on the ground. Man that was poetic.

The Zilla is an IGBT based controller, and not mosfet. I don't know what goes into current limiting in that case. So maybe he can't get around lowering the frequency. A couple days ago Otmar was talking about his throttle control on the EVTech list. He hated how curtis would jerk, and made his so that throttle is related to current (but not linearly), and not PWM DUTY.

Otmar has a variety of motors that he has tuned his PI loops to, if I'm not mistaken, so the hairball either is inputted the type of motor, or it knows the type of motor through some sort of algorithm for finding the correct P and I in that situation. The latter wouldn't be terribly hard. It would be a "getting to know you" time when you first hook up the controller to the car. After a single acceleration from a stop, you could figure out a decent P and I for current limiting.

As it stands right now, a less optimal, but still good solution for me is to find the perfect P and I for my smaller motor (with a slightly larger inductance than a big beast motor), and then cut the P and I in half (or even 1/3), which will make my current limiting less responsive (but still totally un-noticeable), but will make it suitable for a larger motor (like Ben's).