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Thread: 300A VESC in the works, feature suggestions wanted

  1. #51
    TechAUmNu's Avatar
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    Last edited by TechAUmNu; 17th July 2017 at 23:40.

  2. #52
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    Once you have this version working, it might be popular to have a lower powered option with half the FETs populated for drive motors or smaller bots. If the ESC performs well, probably half your sales will be from other countries that run light and mid weight bots.

  3. #53
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    You mean same board with less parts? Yeah that is probably the best way to go for low power versions so I can take advantage of the lower board costs at quantity.

  4. #54
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    Request for quotes on the copper bus bars have been sent out. Hopefully won't be too expensive for 3mm copper lasercut.

  5. #55
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    Have to say I like the method of having a driver per FET rather than one big one for the whole lot. Perhaps not the most cost effective method, but but makes it nice and modular and should make for great switching times.

  6. #56
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    Yeah it lets me run it at much higher switching speeds due to the lower losses. Currently calculations are done with 30kHz but going to 50kHz is only another 10W. Although I am rather worried about the potential 72A peak switching current if everything switched at once lol.

  7. #57
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    Well that'll only be being drawn from the decoupling capacitors near each driver chip, so it'll be spread evenly across the board. Realistically you're only ever gonna be switching 6 FETs on at one time, and if you calculate the impedance of the 6 FETs at 50kHz it's only gonna be drawing an average of about 200mA from the 12V gate drive supply, assuming a 10nF gate capacitance.

  8. #58
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    Do you really need that high switching frequency? For the large, higher impedance motors that this ESC will be used for, manufacturers usually recommend lower switching rates. The ones I am interested in specify a low 8KHz.

    Actually, make that 8 to 16KHz, I think the maunfacturer is basically saying 'as low as your ESC can go'.
    Last edited by overkill; 21st July 2017 at 01:56.

  9. #59
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    Gate charge on the FETs is 172nC at 10v so 17.2nF. So slightly more but still easy to achieve with a fully integrated buck converter. Like this

    They will recommend the lower switching frequency because it reduces switching losses significantly on ESCs with low current gate drives. The main reasoning behind being able to do 50kHz was so it can run very low impedance motors as I think that was one of the problems the original VESCs had? It also lets me plan for worst case possible on heat dissipation so that it will work better at lower switching frequencies.

  10. #60
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    Yeah, with 70A of drive current it's not gonna have any issues with switching at 50Khz! These days I've cranked up switching times on my brushed ESCs to 20khz form 2khz and it makes no real noticeable difference to the temperature once you have more than about 1A per FET.

    Are you only driving it at 10V? Would have thought you'd want about 15v on something like this to help with switching times.

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