30Kw EV Motor Controller

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Dragonoid

Joined Nov 27, 2017
40
Yes... just so many obvious questions... I wasn't even going to go there... hence my question...
I have just Placed the components to get a feel of room available for the Components. The PCB Traces used are exposed copper with 10mmX 10mm Bus Bar soldered upon it to carry the current.
I am working in the heatsink and space constraints as well, Actually, I will be using a T Type Heating that will be connected with the chassis on the Controller it self ( Aluminium block with CNC cut fins)
 

Irving

Joined Jan 30, 2016
1,496
I have just Placed the components to get a feel of room available for the Components. The PCB Traces used are exposed copper with 10mmX 10mm Bus Bar soldered upon it to carry the current.
I am working in the heatsink and space constraints as well, Actually, I will be using a T Type Heating that will be connected with the chassis on the Controller it self ( Aluminium block with CNC cut fins)
Then you need to stop and go back to basics...
10 x 10 = 100mm which is OK for 300A DC. Above a few Hz skin effect applies so your busbar will be a significant heater... there's a reason that EV above a few kW are using several 100s of volts...

My wife's i-Pace has a 388v battery....
 
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Irving

Joined Jan 30, 2016
1,496
And I'm betting the controller doesn't use the TO-220 mosfets shown in his 3D picture.
No, it uses some big IGBT like these (maybe not that brand though)... I'm told they're rated at 400A, 800v, on a liquid-cooled heat-sink... Mind you, to be fair, he's only talking 40BHP against the i-Pace's 200BHP per axle (2-motors)
1620914679205.png
 

shortbus

Joined Sep 30, 2009
8,568
at 400hp, or 300kW, and four three-phase motors, that’s only 65 A per phase, so I suppose it just might. . .
So you think using a mosfet that no matter what the data sheet gives as a current rating, that comes in a package (no matter what else is claimed) is only good for 75amps is going to be reliable? I guess I'm more of a belt and suspenders kind of guy.:)
 

Irving

Joined Jan 30, 2016
1,496
So you think using a mosfet that no matter what the data sheet gives as a current rating, that comes in a package (no matter what else is claimed) is only good for 75amps is going to be reliable? I guess I'm more of a belt and suspenders kind of guy.:)
Agreed, 65A woud need 2 x TO-220 packages, or 1 x TO-247PLUS (aka PLUSPAK247) which is rated 160A
 

Ian0

Joined Aug 7, 2020
2,189
I imagine they would use something that can be replaced using only a screwdriver (or perhaps one of those annoying 5-pointed tamperproof torx thatJaguar likes to use)
 

strantor

Joined Oct 3, 2010
5,543
I have not built a high amp/low volt multi-kW motor drive myself but I once had plans to do so, and I researched it to utter exhaustion. I studied a great many build threads and paid special attention to the ones that failed (which were most of them). I also read accounts of failed commercially available drives (ex: Kelly controller) and got an idea for what works and what explodes.

Drives like the one you've designed (many parallel small FETs) explode. That's how Kelly makes their controllers, and they explode. That's how most hobbyists go about their designs, and they explode. It doesn't matter how well you match your MOSFETs, you can even pay premium for matched sets. The problem is that the voltage drop across the busbar, which can be several volts (and it seemingly doesn't matter how big you make the busbar, same result, and 10x10mm is absolutely insufficient BTW) means each FET sees a different voltage and therefore passes a different amount of current, and one poor little bastard ends up eating most of the lunch and pukes his guts. Now the next one has to pick up the slack and pass even more current than before, so he lets the smoke out too, and so on down the line. In a fraction of a second all the transistors explode.

If you want guaranteed success, you're going to need to pay a premium for a single switching transistor rated for the whole current. And don't just look at the bold font rated current on the first page of the datasheet, that's a bold faced lie. You have to look at the current rating of the package that it's in. I've seen MOSFETs rated "150 amps" in a through-hole package with toothpick legs that would instantly fuse open if 150A was pass through them.

The MOSFET you need is about the size of a cigar box.
 
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strantor

Joined Oct 3, 2010
5,543
P.s.
The MOSFET you need is about the size of a cigar box.
Notice I used singular MOSFET, not MOSFET(s). Because I assume given their price you would only buy one. At least, that was my plan. A single low-side switch instead of an H-bridge. I was going to do the polarity steering with solenoids or big knife switch, and use the single giant MOSFET as a PWM power controller.

You'll also need a ridiculously sized flyback diode to handle the back EMF so you don't murder your high dollar transistor.
 

Irving

Joined Jan 30, 2016
1,496
The MOSFET you need is about the size of a cigar box.
Much is true, though there are perfectly good designs out there that do use parallel MOSFETs in the sub-10kW space. Most EV-scale controllers now use IGBT rather than MOSFETs in the large matchbox sized pack I showed in post #13 (rather than cigar-box size). And they are 3-phase half-bridges.
 
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