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Old 08-19-2012, 09:51 AM   #61
kimmik
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Very well thought through video, good stuff!

I've wondered for long time too why so few escs adopt afw. In fact when i first got into bldc motors, i assumed that they ALL used afw, because not using it is just silly.

Programming it should be easy too right? Invert the high side gate control, add delay.
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Old 08-19-2012, 10:13 AM   #62
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Great explanation in the video!

I was on the right track, they are just flyback loops, active gets an efficient fet, passive gets an inefficient diode.


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Old 08-19-2012, 11:06 AM   #63
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Quote:
Originally Posted by Iceberg86300 View Post
Great explanation in the video!

I was on the right track, they are just flyback loops, active gets an efficient fet, passive gets an inefficient diode.


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Yep. Indeed your correct.

Free-wheeling detailed explanation in this post

Last edited by Mercuriell; 08-19-2012 at 04:24 PM..
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Old 08-19-2012, 11:08 AM   #64
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Programming the AFW is quite difficult. The software makes the difference between good and bad AFW.

Regards, Hemut
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Old 08-19-2012, 11:17 AM   #65
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Quote:
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Programming the AFW is quite difficult. The software makes the difference between good and bad AFW.

Regards, Hemut
Yep that's correct, its much more difficult than some might think.

Timing is critical, and if your phase runs out of residual current, you will be basically just applying brakes (by shorting the phase). This is called discontinuous mode.

The idea scenario is to measure the phase current, and when current stops flowing, you turn-OFF the free-wheeling MOSFET.

regards
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Old 08-19-2012, 11:45 AM   #66
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Quote:
Originally Posted by ub3r View Post
Yep that's correct, its much more difficult than some might think.

Timing is critical, and if your phase runs out of residual current, you will be basically just applying brakes (by shorting the phase). This is called discontinuous mode.

The idea scenario is to measure the phase current, and when current stops flowing, you turn-OFF the free-wheeling MOSFET.

regards
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Ahh...that's what I was missing. I was thinking the added efficiency of the FET would result in an opposing electromagnetic force that would brake the motor.

When the reverse EMF spike current drops and the FET switches off, what happens to the generated voltage on the coil? Does it just float? It would be the wrong polarity to conduct through the protection diode, right? Or am I confused?

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Old 08-19-2012, 11:54 AM   #67
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Quote:
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Ahh...that's what I was missing. I was thinking the added efficiency of the FET would result in an opposing electromagnetic force that would brake the motor.

When the reverse EMF spike current drops and the FET switches off, what happens to the generated voltage on the coil? Does it just float? It would be the wrong polarity to conduct through the protection diode, right? Or am I confused?

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Your not confused. Your actually perfectly right.

The Generated voltage floats between GND and Supply, and the voltage seen on the phase is proportional to the torque ripple..
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Old 08-19-2012, 12:07 PM   #68
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Tony, somebody already asked for adding a Hobbyking YEP ESC to your test. I also think this would turn your test to a really interesting one.
Why? Especially since YGE officially stated on their homepage, that the YEP ESCs are (more or less) a 100% plagiarism of an older revision of their YGE ESC. YGE said that also the software of the ESC was stolen 1:1.

So it would be quite interesting how the YEP performs in comparison to the YGE.

Regards, Hemut
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Old 08-19-2012, 12:10 PM   #69
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Hemut, I'd be more than happy to do a 1v1 comparison of the YEP vs YGE.
Just need more time as i haven't even finished these tests.
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Old 08-19-2012, 12:24 PM   #70
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Tony, that's only a suggestion from my side. You decide what you are doing in your test.

Regards from Austria
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Old 08-19-2012, 06:36 PM   #71
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From what I observe on the yep esc afw mode, it has either no ability to detect the end of freewheel current or an inaccurate detection, and suffers a big rpm discontinuity when going through a certain throttle.

This issue is relieved with some load eg blades.

So what esc has the best afw programming in your perspective, hemut and tony? And for what reasons?
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Old 08-19-2012, 07:27 PM   #72
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Quote:
Originally Posted by kimmik View Post
From what I observe on the yep esc afw mode, it has either no ability to detect the end of freewheel current or an inaccurate detection, and suffers a big rpm discontinuity when going through a certain throttle.

This issue is relieved with some load eg blades.

So what esc has the best afw programming in your perspective, hemut and tony? And for what reasons?
So far, from what Ive seen, the KOSMIK is ahead by light years.
Even the Power-Jive struggles a little with low load.
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Old 08-19-2012, 07:30 PM   #73
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If k implements the kosmik mcu in the next jive I'll be all over it
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Old 08-20-2012, 12:26 AM   #74
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would you be testing the scorpion 130A ESC too
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Old 08-20-2012, 01:31 AM   #75
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I also would say that Kontronik has the best AFW. Also Gov and smooth spool-up is the best.
Because of that the Jive is well established on the market since years. The Jive is an absolute carefree package.

The Kosmik is new on the market. So we have to wait, until more users got their hands on it. The Kosmik has an extreme smooth spool-up. It looks like a real heli. So this feature is very nice for big electric scale helis.

The Kosmik is quite big and strong. I would say, the Kosmik is too big and not necessary for a 700 heli.
I will use a Helijive with a 4530 for my Banshee. With good cooling the Jive can handle peaks about 240A without problems.

Regards, Helmut
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Old 08-20-2012, 01:57 AM   #76
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This thread is really enlightening... Well done ub3r on the clear and concise explanations, and an excellent test!
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Old 08-21-2012, 02:07 AM   #77
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awesome thanks for the post on AFW you didnt need to go that far a link to a wiki or some thing would of been fine
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Old 08-21-2012, 02:47 AM   #78
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Thanks Ub3r, my line of work is electronics too, not a clue about ESC specifics though, so very enlightning for me too and appreciate the effort.
Assume you are the same guy that looked into CC problems a while ago and impressed Patrick: http://www.rcgroups.com/forums/showt...1450849&page=7

Great to have a real independant authority on ESC's although pretty well hooked on Kontronic, shame about the costs though, but for piece of mind .

Great to understand the theory though and testing though.
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Old 08-21-2012, 06:03 AM   #79
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Discussion on AFW in YGE clone moved to Electronics Forum here
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Old 08-23-2012, 11:33 PM   #80
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Hey tony if you get a chance, i'd like to nominate pwm as your next point of discussion. I'm interested in a detailed breakdown and estimate of the pwm esc losses and pwm motor losses.

In particular the effect of fet drain source charge, voltage, current, switching frequency, afw on the switching losses. Would be nice to have a general idea of how much total loss it is.
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