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ACM now uses 12 MOSFETs instead of 6


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4 hours ago, TremF said:

Well they haven't been using the boards for a couple of weeks. Jane confirmed with Gray that we have the original board which means whatever they did when they held onto our ACM's for the low speed frying issue wasn't the board.

Although you're saying it's not the board, do you know if the new board can just be swapped in or are there other changes for the current configuration?

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9 minutes ago, John Eucist said:

Although you're saying it's not the board, do you know if the new board can just be swapped in or are there other changes for the current configuration?

When someone asked about purchasing the new board on FB Jane asked if the motor was HB or QJ but didn't say the significance or which was needed for the new board to be compatible.

I'm not sure if the change they held my ACM back for before dispatch was just software related. Answers don't seem to be very forthcoming or informative. 

I just want my ACM working correctly. It's a lot of money for it to keep dropping on me and getting more scratched up.

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3 minutes ago, TremF said:

When someone asked about purchasing the new board on FB Jane asked if the motor was HB or QJ but didn't say the significance or which was needed for the new board to be compatible.

Hope they get an answer soon so we know.

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51 minutes ago, TremF said:

When someone asked about purchasing the new board on FB Jane asked if the motor was HB or QJ but didn't say the significance or which was needed for the new board to be compatible.

I'm not sure if the change they held my ACM back for before dispatch was just software related. Answers don't seem to be very forthcoming or informative. 

I just want my ACM working correctly. It's a lot of money for it to keep dropping on me and getting more scratched up.

Oh dear. Still work in progress? The ACM is a milestone but it was published to early.

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5 hours ago, TremF said:

Not sure exactly because I have never had this before with my Ninebot. It's a bit like getting on without turning it on and when you go to lean it falls over. 

Again: WOW!

I have never had a Ninebot, but i have a KS14 and a KS16...and i also NEVER had such a Situation on one of both!

After i started the machine, you normally just registrate it without doing anything that the power is on (the machine just stays clearly horizontal)......

And it never just dropped to front or back when i stepped on it......

 

on the KS16 when i start -directly- with "idling"...i sometimes got an "Caution Overpowering" Warningn (a known FW 1.13 Bug)....but even then the new KS16 never looses it's power and dropped ......

 

I would not have a very big "trust" in such a wheel.....may such a behavior come from a KS or GW or 9B or whatever.....something seams seriously wrong.....

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4 hours ago, Chriull said:

Additionaly by paralleling the mosfets the total power dissipation can quite easily be reduced. Due to the fixed Vce-sat power dissipation cannot be reduced with IGBTs - just distributed.

So the voltage, current and frequency used in EUC's nowadays can be handeled easily by both. Just in this operational range Mosfets perform far superior in regard of power dissipation. And cooling seems to be by now one of the bigger problems with the new EUCs.

The IGBT might be more appealing if you increased voltage and reduced current over existing EUC designs. Most of the IGBTs support 400V. The biggest advantage is you can buy IGBTs in intelligent power modules. You get the 3 phase half bridge plus gate drivers  all in one sealed package and attached directly to the heatsink. Both silicon mosfets and IGBT appear to be being replaced by SiC and GaN based mosfets, they handle 600v have much lower switching losses than silicon, only downside is price and the GaN ones need 5V gate drivers instead of 15V.

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6 hours ago, TremF said:

Not sure exactly because I have never had this before with my Ninebot. It's a bit like getting on without turning it on and when you go to lean it falls over. 

Could it be that your ACM is not calibrated correctly?  Perhaps your ACM was slightly tilted to one side but it already triggered the auto-shut due to being calibrated incorrectly?  I have this old video explaining calibration (including stressing the sideways calibration) for the old MCM but I think it's the same concept for the ACM.
 

 

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1 hour ago, John Eucist said:

Could it be that your ACM is not calibrated correctly?  Perhaps your ACM was slightly tilted to one side but it already triggered the auto-shut due to being calibrated incorrectly?  I have this old video explaining calibration (including stressing the sideways calibration) for the old MCM but I think it's the same concept for the ACM.
 

 

 

I put my phone with a spirit level on top and it wasn't very far out. I have got it as close to 0 0 as I can and will see how it goes when I am next out.

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  • 1 month later...
On 6/23/2016 at 0:20 AM, lizardmech said:

I'm not sure having 12 makes any sense, this is a 180A fet. 12 will produce more heat but spread over more fets. If the limitations in cooling are a result of heat being unable to escape the shell 12 fets will be worse.

It makes a lot of sence since the current going per Mosfet is half and the mosfet is not pushes beyond specs, while with a single mosfet as it is pusdhed closer or beyond its specs it looses efficiency as efficiency is lost more heat is generated as more heat is generated the mosfets become less efficient in turn generating more heat, eventually self destroying themselves. Therefote having 12 mosfets solves part of the problem, the only problem left is to remove the heat from the heat sinks.

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To add to what @checho said, the max current rating for a mosfet is given assuming the maximum junction temperature is not exceeded. So it can handle that current only as long as it's not generating so much heat that it reaches the max junction temperature. 

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19 hours ago, dmethvin said:

To add to what @checho said, the max current rating for a mosfet is given assuming the maximum junction temperature is not exceeded. So it can handle that current only as long as it's not generating so much heat that it reaches the max junction temperature. 

Also, some sources state that the TO-220 -package legs start to be around their limits above 75A continuous current (guess it depends on how much of the legs is left between the case & the board, though), so even if the internals of the mosfet could take 200A, the legs might become the limiting factor :P

But, since the current is pulsed with PWM, the package itself could withstand more current (as it's not continuous).

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For that 12 Mosfet Thing i personnaly believe more in what Chris from 1Radwerkstatt has said...who is repairing and selling EUC's all day Long:

Quote of another topic:

  • But i can say (this is real) 12 Mosfet´s is electrical trash!(you can make this on hobby table when you have not the right parts on hand) You can stack stones for a wall but not MosFet´s for HighPower......
  • ......When you double MosFet´s on one side is split current but Energy is fast and very exact one MosFet switch faster on later one is internal a little bit different and more stress to the gate driver...many electrical things...other side you double the failure in MosFet self....wrong way is stacking...
  • You can buy one MosFet with can handle hundreds of Ampere or a module with 6 matching MosFet´s in one case...this and only this is the right way.
  • Problem in all Wheels is mounting a MosFet correct...first: stupid 1mm thick heat conductive rubber (stupid stuff) second: mounting in the corner from the heat sink third: mechnical stress...screw mosfet with soft rubber on heat sink.....all not OK.... one industrial case (IGBT) with correct internal mounting and.....work
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3 hours ago, KingSong69 said:
  • You can buy one MosFet with can handle hundreds of Ampere or a module with 6 matching MosFet´s in one case...this and only this is the right way.

The question about matching is a reasonable one, perhaps Gotway is doing some component testing to find mosfets with closer matching specs. Note that even companies like Tesla decided not to go with a commercial power module and instead built their own out of discrete components. 

http://www.pointthepower.com/on-tesla-electric-vehicles-semiconductor-packaging/

Several reasons listed there for going with discrete components could apply to EUCs as well: manufacturing volumes, available form factors, heat spreading concerns, simplicity of assembly, and so on.

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On 7/29/2016 at 8:37 AM, dmethvin said:

Several reasons listed there for going with discrete components could apply to EUCs as well: manufacturing volumes, available form factors, heat spreading concerns, simplicity of assembly, and so on.

Another possible factor could be the 'moreism' principle = the mistaken belief that more is always better. In a serialized system like a EUC, the addition of 6 additional MOSFETs could in fact make it less reliable, considering the newly introduced possible points of failure. 

With the advent of the 1200W motors, we're seeing the weaknesses of moreism being played out by the frequent reports of cut-outs, overheating, or other failures. I very much doubt the principle exponents of these designs have asked themselves: 'how much continuous power is actually really required?' 'are all the other elements in the design—mainly the control-board—up for the job?' 'What are the associated drawbacks—Increased energy consumption, reduced braking distance, etc...?' 

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25 minutes ago, Jason McNeil said:

Another possible factor could be the 'moreism' principle = the mistaken belief that more is always better.

Good point. We are sometimes just chasing the limits from one component to another as we add "more" to one thing, and not necessarily making the complete system any better or more reliable.

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14 hours ago, dmethvin said:

Good point. We are sometimes just chasing the limits from one component to another as we add "more" to one thing, and not necessarily making the complete system any better or more reliable.

+1. 

the main prob is imho still the proper heatsink design. There are with most wheels still major design issues - from the choosen insulation material, to the positioning of the mosfets on the heatsink/aluminium plate (all on one side), thermal paste application (too much - instead of a minimal even distribution!), mechanical attachment, air convection possibilities, etc...)

also i do not know the exact actual design used by now with the acm imho there should be quite some improvement possible by paying some money to a _real_ expert. Just If this expert states that with this "safe and easy methods" (heatsink design) a proper cooling cannot be reached, the next step would be to go from 6 to 12 mosfets, which can (if again properly designed) cut the dissipated power and so the heat probs by half. But this only makes sense if there is a proper heatsink design - the heat by the dissipated power has to be removed by convection/air movement first! If this is not the case, one can use as many mosfets as one likes without really improving the situation! 

And if the heatsink is properly designed one again would need an experienced professional to solve the design issues for paralleling mosfets  like component preselection, gate decoupling, separate drivers for each mosfet, feedback loops to ensure timely switching behaviours of each mosfet - needed complexity depending on the thermal/power dissipation bottlenecks for the different use cases arising driving the wheel. And this  use cases/test case analysis again needs some professional efforts to ensure proper design decissions for a safe wheel.

imho the development state by now is just some trial and error evolution and no real design decissions/calculations from experienced professionals...

this post is not indented in any way as a gotway bashing - this company is quite state of the art of nowadays ewheels! It is more a "nowadays state if the art ewheels bashing". Like the introduction of electronic systems by the automotive industry almost decades ago lead to quite some disaters which needed "endless" time to be resolved. until now it seems that this gathered experience is not used by any ewheel manufacturer nowadays... :(

...and this are just hardware issues - the firmware could need quite some more professionability, too...

edit: i forgot to write that i love the actual ewheels! And the actual "shortcomings" forces one to think  a bit while riding - adopt the speed for bumps, inclines etc and be a bit carefull to explore the limits. Also some people get an reason to loose weight, which is not the worst thing :ph34r: i get these thought also when i see my brother zooming up the hills and using much less battery than me...

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1 hour ago, Chriull said:

imho the development state by now is just some trial and error evolution and no real design decissions/calculations from experienced professionals...

"Trial and error evolution"... That sounds just like my projects! :D

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  • 1 year later...

Interesting read and kinda looking if I can find any ACM 12 mosfets DIY improvements, but of course they need to be improvements hence knowing what I am doing unless just following someones else example and just soldering a bit. Fun read nevertheless.

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