I’d say that comparison is fairly apt. BLDC has a more raw feel to it. FOC is smoother and more refined. It is said to be a bit harder on the vescs in FOC than in BLDC. My controllers have never had an issue with either. I think it’s just more important that you program your controller correctly.
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& FOC can lower your top speed by a couple mph…
is the top speed lower in foc due to lower power? id have thought the speed limit was due to the motor design and pack voltage. is the speed lower in foc doing a no-load test? ive only ever run foc and never done a no-load test in bldc. easy test
Looks like Mr. Vedder answered this question over at Vesc-Project.com:
benjamin ( https://www.vesc-project.com/node/218 ): “Pure FOC compared to pure block commutation gets slightly lower top speed as the sine voltages would be distorted otherwise as they are in block commutation. Also, the VESC is limited to 95 % modulation and the other ESC might come a bit closer to 100%.”
No.
FOC: Imagine you have a wind mill, and you have three tubes with air coming out of them. The air is the current, the current can increase, and the tube exits stays the same size, because all three are modulating at once.
Bldc: Imagine the same scenario, but instead of all three tubes having air come out of them, pairs of 2 have the equivalent current coming out of them, in a 6 step sequence. Since the same amount of current is coming out of two tubes, as three for FOC, the velocity coming from two is faster.
Basically in really simple easy to understand terms. The same current, in the same rotation time span, is burst out of two tubes, then two different tubes etc. The result is the higher air velocity setup spins fast. But is less efficiently.
here’s a chart I found showing BLDC “block commutation” @ 100% duty cycle:
^notice with BLDC only 2 of the phases have current at any given time and these are not “sine waves”
the reason I called this “trapezoidal” previously rather than “block” is, due to the inductance of the motor windings, the current does not in fact rise and fall instantly, giving a slight slope to the sides of the blocks, making them in reality appear slightly “trapezoidal…”
here’s a different chart comparing the “block” commutation with “sinusoidal” commutation:
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here’s my attempt at an animated gif of the current plot for comparison:
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PWM
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10 characters.
A rule of thumb is to use BLDC on all VESCs 4.12 except for the Focbox. Only Focboxes and VESC 6 are capable of reliably running FOC.
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You’ve run FOC successfully on your VESC 4.12 for a long period?
I really liked that video, sounds like kahn
For thousands of miles on multiple boards, yup…sensored foc on hk vesc…proof is in the real world testing for me, not your opinion…
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Yeah but is that thousands of miles going 20km/h cruising speed on flats or 40km/h with hills. What’s the top speed you’ve achieved on your build?
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Dude, respectfully you are wrong. I’ve got an Arbor Vugenhausen with a TB VESC, 10s3p, 90mm flywheels with almost 3000 miles on it. I throw it in the back of my truck all the time, I loan I out to n00bs, I’ve ridden to 30mph, ridden 10 mins up a hill.
I have actively tried to blow it up so I can use the deck to build a dual off-set and it just won’t die.
If you use good wire, make good solder joints, use quality cells and config correctly there’s nothing wrong with using a v4 VESC for FOC…those same rules should be applied to any build.
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I guess I was wrong. I swear I’ve read from many senior members posts about FOC being a gamble on 4.12 with the exception of Focbox. Could it be that running it on 12S FOC is a no no.
So could u potentially have 1/3 less stator saturation w foc…so third more torque? Because all three phases are used so all teeth as appears to 2/3 of the teeth?
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