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by devin
10 May 2017, 11:26
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

. If you really want to waste exactly 1000 W at 0 rpm, then limit battery current to 1000 W/46 V = 21.7 A, or for 1000 W loss in the motor, limit motor current to [P = I²R -> I = (P/R)^0.5] (1000 W/0.0415 Ω)^0.5 = 155 A. Thank you! "Wasting" exactly 1000w electrical full throttle as close...
by devin
09 May 2017, 22:43
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

benjamin, trying my best to understand. i'd like to be able to write an equation to predict which amp limit settings will give a predictable wattage as close as possible to 0rpm full throttle. i've had trouble locating documentation on the topic of predictable motor amp limit effects on acceleration...
by devin
09 May 2017, 18:48
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

i don't think the motor behaves as an inductor circuit during the "off" portion of the duty cycle.

i think there is an amp "cliff" effectively to 0a immediately after each pulse.
by devin
09 May 2017, 16:31
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

So let's use those detection values 0.0415ohm detected x 2 = 0.0830ohm winding 27.13uH detected inductance 46v pack voltage with sag predicted for full throttle, 1000w electrical at all possible rpms including very close to standstill full throttle is desired. 109.76 motor amps x 0.0830ohm = 9.11 pw...
by devin
09 May 2017, 15:29
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

in the case when @hummie rode his board for a week with 48/200/200 batt/motor/absolute settings, assumed battery voltage with sag was 35v, his detection was: http://tppsf.com/h.jpg http://tppsf.com/48-200-200-1.png video of the 48/200/200 hub motor setup running on test bench (was subsequently ridde...
by devin
09 May 2017, 13:57
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

My understanding is that it would, and that each 70.71 average amp pulse would look like a "ramp" in the motor wires from the inductance, and because 70.71 amps is the average, that the pulse would start at 0 amps and rise to 141.42A at the peak (double the average). Each pulse would be 30...
by devin
09 May 2017, 13:54
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

@Benjamin In a hypothetical scenario: I put a motor in a clamp so it can't rotate and I simply want to put 1000w pulsed dc electrical through any 2 phase wires. Earlier a vesc detection revealed 0.1 ohms winding (x2 = 0.2ohm) on the motor, and I have an ideal 46v Dc power source. Would constant 46v ...
by devin
09 May 2017, 13:21
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

The 71 amps are continuous and not modulated for a fraction of time. The modulation is what turns the 22 battery amps into 71 motor amps. There is no way you can draw 1kw from the battery and produce less than 1kw of heat when the mechanical power is close to 0. But: -duty cycle means % on time. -i...
by devin
09 May 2017, 13:11
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

But I think 70.71 amps for 30.73% of the time produces as much heat as 21.72 amps for 100% of the time.

I dont think 70.71 amps for 30.73% of the time produces as much heat as 70.71 amps for 100% of the time.
by devin
09 May 2017, 13:08
Forum: General
Topic: How should the VESC "feel" on a board?
Replies: 71
Views: 20391

Re: How should the VESC "feel" on a board?

My point is I respectfully dont agree with you that motor heating would be equivalent to 71 amps in the example. I believe it would be equivalent to 22 amps.

71 amps for 30.73% of the time produces as much heat as 22 amps for 100% of the time.

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