Who is using FOC and whats your setup?

Wow leave it to someone on Vedder’s site to figure it out!! Talk about crunching numbers…id have chalked it up to the same maybe but with no math. One day I’ll do a test to see how far I can get on the big bike track here.

That is a fascinating post
So it seems there should be a formula to figure out the best speed for efficency
Given a particular are set-up
Seems that 4kmh difference was huge

I just glanced at the reply in Vedder’s site and I’m interested to try to read it but I doubt u can quantify the wind resistance of higher speeds and it’s also a huge influence. It’s so easy to change the frontal area by simply bending forward or crouching. I’ve laid (or lain) on my board going downhill, unpowered, and I can get way farther

hmmm, interesting - yesterday I made my longer commute trip to and from work and that one has a long semisteep rise, maybe 10%, but over 1km or so. first time I ran that rise with FOC and my new 168KV 6374 motor, the vesc didnt get hot enough so that it would go into soft off strategy after 80°C (which my tesseract always did with 190kv motor). now, with BLDC instead of FOC, the setup got so hot again that the vesc powered down after 80°C.

it seems that in the exact same setup, with the exact same speed uphill, FOC mode ran the vesc cooler than bldc? speaks for a better efficiency of foc. gah, why does it keep killing my vescs :weary:

i remember reading on vedders site that he needed an extra cap on c18 to prevent errors, though I’m not sure it was the error as yours.

Have you read this, maybe it can help explain ?
The Difference Between Motors Commutation BLDC vs (FOC Trapeziodal / Sinosuidal)

Seems to say FOC will have less speed ,…but more torque,

But why are some people blowing chips? That’s the question that doesn’t have an answer Randy. When it works it’s great till it’s not working. I’m still going!

Hummiemotors are safe with FOC. :slight_smile:

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call me crazy, but tonight I flashed back to FOC to test the max range again once more. for testing I gave it the beans - full throttle for 20min straight pretty much, including the long 1km 10% rise where BLDC mode usually powers down from overheating. FOC really just pulls up there, no powering down, nothing. impressive :open_mouth:

fingers crossed that this time everything works out - overall FOC rides more enjoyable, against my first impressions its even at mid and highspeed more silent than bldc. basically same motor basis sound, but no high pitched BLDC hum.

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Didn’t you say in an earlier post that BLDC was the same loudness as FOC at high speeds?

well, the motor sound itself is quite loud, in bldc and foc. but the high pitched bldc sound adds ontop of that - more pronounced at low, less audible at intermediate to high speeds, at least for my old ears :stuck_out_tongue:

I’m surprised you decided to go back to FOC considering your luck with it so far. Hope you don’t blow another drv! What VESC are you using btw?

got 2 backup vescs from my trampa right now - just learnt that the guy who bought it wont pick it up for another 3 weeks :grin:

Does this seem to correspond to the linked article ? …Less speed more torque?

I had less speed than bldc yea, 43kph bldc, 41kph foc on flat straights!

torque is hard to tell, its very similar and hard to be objective when the low speed sound is so different. foc feels very solid and nothing can be heard, bldc hums like an angry bee so it feels more agressive but it certainly isnt. got a fairly steep rise in front of my house and both modes have a hard time getting the board up to speed with 50A battery, 70A motor current max setting.

2 reasons I want foc: temperature most of all since vesc shares the enclosure with my liion cells, and sound is just more pleasant, especially low speed. I came across 2 police patrols this commute week and had a hard time silencing the board with bldc so I wouldnt turn heads (had to reduce speed quick to pretend pushing). :yum:


now for the this time in FOC motor parameter recognition, I removed the belt to allow the motor to spin freely. it might be something thats just in my head, but it feels the motor runs better, even smoother than first time foc. startup is much better for example. first time foc parameter recognition, the motor had a hard time starting up on its own for the bench test - now it starts really smooth without any hesitation.

could also be the silicone wire mod, which I did without re-doing the FOC parameters - maybe the resistance changed and the motor parameters actually werent ideal?

if you have a chance check out the live ERPM curve in the BLDC tool and compare FOC to BLDC its amazing how smooth FOC is literally,
and how jagged BLDC is. I have to image that that smoothness is better for the system all around. BLDC is hundreds of little spikes.

ran another max tour with foc this time: 48km with an estimated average of 23kph, down to 30V and I had to push the last 400m :yum:

also managed a new top speed of nearly 44kph, but that was admittedly slightly downhill. :stuck_out_tongue_winking_eye:

sadly got a severe case of roadrash which explains the “break” in the split table … ran off the road to get to a bike lane with nearly full speed downhill and the connecting 3meters were pretty much behind a bush, so i couldnt see that it was gravel instead of good old concrete ARGH. :dizzy_face:


Maybe i found the reson for the blown up VESC’s when you switch from BLDC to FOC. In the motor configurations advance tab there is the window for Max current ramp step (at 1kHz).
This value increases by the factor 10 when you press the read configuration button. Wehn you write that value and read it again then it increases again by the factor of 10. In my case it was at 50000. Default is 0,04.
That is a bug in the BLDC Tool 2.18.

So it is very easy to bring this value up to 50000 by accident. I don’t know exactly which impact this value has, but from 0,04 to 50000 doesn’t sound healthy.


It has been corrected in github at 27th June, so if you want to upload the newer FW 2.18 you need just to recompile it.

I’ll upload it this evening on my website.