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They already have Kapton in a few odd places, so yeah I suppose that would work.Tesla could fix observation #2 with some Kapton tape or other suitable insulator.
Cheaper to replace the aluminum bracket. All they need to do is change this mounting tab from 45 degrees to 90 degrees, just like the other tabs. My guess is the EE who designed the PCB specified all tabs at 90 degrees, and then at some point the ME team changed that one tab to 45 degree to save a few pennies in the folding process.Fixing observation #1 would be harder, likely a replacement inverter board.
Could they not just use a Dremel like small grinding pin and do it in place?...
Cheaper to replace the aluminum bracket. All they need to do is change this mounting tab from 45 degrees to 90 degrees, ...
I meant to respond to this but forgot, sorry.Thanks for the comments, @furuike. PCB is an ordinary fiberglass, as determined by abrading the top surface to determine the weave structure. Probably a 175-class FR4, based on my experience... could be up to 600, but that would still require much more spacing than observed.
Supporting evidence: everywhere else on this PCB, Tesla has gone to GREAT lengths - and wasted tons of PCB real estate - to maintain at least 4 mm spacing between isolated modules. It seems odd that Tesla would properly enforce 4 mm clearance all over this PCB - particularly in those high voltage areas close to the aluminum bracket - except for at this one spot, which for some reason has more than an order of magnitude less spacing (i.e. 0.38 mm).
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Do you have any thoughts on the exceptions listed in UL 1741 24.1.1? Particularly #7, which would require 0.8 mm regardless of interlayer material type? Note that #7 doesn't exactly apply to this issue, but is the least amount of required clearing I've found so far for a design like this.
Do you have any thoughts on UL 1741 25.4(b), which requires inverters to comply with Overvoltage Category IV spacing requirements (instead of Category III)?
Do you have any thoughts on UL 1741 25.4(h), which requires adherence to UL 840 spacing requirements?
...
To reiterate, I would love for Tesla to provide more information about their certification process. If they would only just respond, maybe we could close this issue out in five minutes?
By your 0.38mm estimate, this is not a standard 1.6mm/0.64" thick PCB?Thanks for the comments, @furuike. PCB is an ordinary fiberglass, as determined by abrading the top surface to determine the weave structure. Probably a 175-class FR4, based on my experience... could be up to 600, but that would still require much more spacing than observed.
1.6mm is a typical PCB thickness, but PCBs often have more than 2 layers. Distance between internal layers are less. I'm less familiar with UL 1741, but other standards I am more familiar with are OK with fairly high voltages between layers on PCB layers because there is solid insulating material (prepreg) between them.By your 0.38mm estimate, this is not a standard 1.6mm/0.64" thick PCB?
0.38mm = .015 inch, so only 100V/mil is needed for 1,500V main transient ignoring the other elements:
Soldermask can be >500V per mil
Conformal coating >1000V/mil
Also, if I'm viewing this correctly, the bracket is attached via a press nut so it is airgapped from the PCB.
View attachment 1008533
Right, but given the description, it seems to be two layer. Bracket is adjacent to 1 and they show the trace on the opposite side and call it layer 2. If the inner trace was biased to the attachment side, it seems like that would be shown instead.1.6mm is a typical PCB thickness, but PCBs often have more than 2 layers. Distance between internal layers are less. I'm less familiar with UL 1741, but other standards I am more familiar with are OK with fairly high voltages between layers on PCB layers because there is solid insulating material (prepreg) between them.
Yah, I understand creepage and clearance. With sufficiently insulated conductors, there is no creepage nor clearance requirement.The fact that there is an airgap is not necessarily OK, it depends on the distance as there are minimum clearance numbers you must maintain from line to ground. There are also creepage numbers (across a surface like the top of bottom of a PCB) that you must maintain. Typically creepage numbers are much larger than clearance numbers.
Yes, thinking about this more I'm less certain it's a problem. OP wrote:Right, but given the description, it seems to be two layer. Bracket is adjacent to 1 and they show the trace on the opposite side and call it layer 2. If the inner trace was biased to the attachment side, it seems like that would be shown instead.
Like your experience, the interlayer is insulation anyway and 0.38mm seems sufficient.
Yah, I understand creepage and clearance. With sufficiently insulated conductors, there is no creepage nor clearance requirement.
That the bracket does not appear to mount flush to the board seemed relevant when addressing item 2: "Therefore, there is no conformal coating where the aluminum tab intersects the board edge."
Is this assuming a delamination of the PCB then jumping the air gap?
How does OP know that the 0.38mm is primarily FR4 and not prepreg? How many mils of prepreg would be required for adequate spacing for observation #1?The copper on layer 2 is approximately 0.38 mm below the PCB top surface (layer 1).
Prepreg can also be FR-4 material. FR4 type is >20kV/mm so even 0.38mm is sufficient for mains and transients. I think transient is 1,500 working is only 160V peak for US split phase.How does OP know that the 0.38mm is primarily FR4 and not prepreg? How many mils of prepreg would be required for adequate spacing for observation #1?
I think I don't entirely understand the geometry in question for observation #2. My understanding is that there mains trace comes to the board edge and there is inadequate air clearance from the side of the PCB to the aluminum bracket. Or else the mounting screw / insert on the board has inadequate surface creepage to the mains trace on the bottom.
If the board is indeed just two layers, then there would be no prepreg, just FR4, Cu, and soldermask layers, and as you say as much as 1.6mm between the traces. But then I don't understand why OP says 0.38mm if the issue is between traces on the top and bottom. Maybe a through via?Prepreg can also be FR-4 material. FR4 type is >20kV/mm so even 0.38mm is sufficient for mains and transients. I think transient is 1,500 working is only 160V peak for US split phase.
It comes near the edge. To conduct via creepage or clearance, there would need to be voids in the layer. Then it's a matter of the stand off distance and path length to the bracket.
Although, it could be that the bracket attaches to the visible side, in which case the access cutouts are there for push nut insertion, not assembly.
You should follow the installation guidance on the particular products that you are installing. They are generally pretty specific on where and how the sensors should be installed. Heat(p/smoke/flames all rise...As an end user with two PW2’s in garage attached to interior wall, what is recommend heat/smoke alarm and install method where ceiling height is a factor; can heat sensor go on the wall just above PW or would it be preferable to build a small shelf from wall so heat sensor is directly above PW casing?
And would 12 inches be appropriate height above Powerwall or something like 24 inches?
Yes, I’m aware of heat rising so ceiling would be logical location but the height and size of the room suggests something lower would be more sensitive, although ceiling likely captures and pools the heat so likely best option despite the distance from the source of the heat.You should follow the installation guidance on the particular products that you are installing. They are generally pretty specific on where and how the sensors should be installed. Heat(p/smoke/flames all rise...
Read the manual of your specific device. Not all devices are designed to allow being wall mounted and still maintain effectiveness.Yes, I’m aware of heat rising so ceiling would be logical location but the height and size of the room suggests something lower would be more sensitive, although ceiling likely captures and pools the heat so likely best option despite the distance from the source of the heat.
No, a new bracket is required. Without that tab (e.g. if you remove it with a Dremel), the 16 pound PCB assembly could flex during transit, which is never good for electronics.Could they not just use a Dremel like small grinding pin and do it in place?
Total PCB thickness is 2.7 mm. IMO this isn't thick enough considering the PCBA weighs 16 pounds.By your 0.38mm estimate, this is not a standard 1.6mm/0.64" thick PCB?
You are not viewing this correctly. The entire aluminum bracket profile is coplanar to the PCB top surface.Also, if I'm viewing this correctly, the bracket is attached via a press nut so it is airgapped from the PCB.
Clarification: FR4 is technically a type of prepreg, but I understand your general question. Based on my most generous reading of the code, the absolute bare minimum distance between line and chassis is 0.8 mm, no matter what material is placed between said distance. However, a more strict interpretation (and probably the correct one) is that the minimum distance is not less than 3 mm.How does OP know that the 0.38mm is primarily FR4 and not prepreg? How many mils of prepreg would be required for adequate spacing for observation #1?
Correct: L2 mains trace is too close to the aluminum bracket, both directly through the prepreg+solder mask+conformal coating (0.38 mm), and the exposed milled edge (trace distance to edge+0.38 mm).I think I don't entirely understand the geometry in question for observation #2. My understanding is that there mains trace comes to the board edge and there is inadequate air clearance from the side of the PCB to the aluminum bracket. Or else the mounting screw / insert on the board has inadequate surface creepage to the mains trace on the bottom.
6000 V as used in this application.Prepreg can also be FR-4 material. FR4 type is >20kV/mm so even 0.38mm is sufficient for mains and transients. I think transient is 1,500 working is only 160V peak for US split phase.
There is no standoff distance; the bracket is exactly coplanar with the PCB top surface. The PEM nut does not contact the PCB; it's on the opposite side of the bracket.It comes near the edge. To conduct via creepage or clearance, there would need to be voids in the layer. Then it's a matter of the stand off distance and path length to the bracket.
Although, it could be that the bracket attaches to the visible side, in which case the access cutouts are there for push nut insertion, not assembly.
The plane of the PCB is vertical?Total PCB thickness is 2.7 mm. IMO this isn't thick enough considering the PCBA weighs 16 pounds.
PCB has QTY4 total layers, with QTY2 layers glued to each side of a ~1.9 mm core.
You are not viewing this correctly. The entire aluminum bracket profile is coplanar to the PCB top surface.
Specifically, the stackup is: PCB||bracket||PEM nut.
Why 6kV?6000 V as used in this application.
Based on my most generous reading of the code, the absolute bare minimum distance between line and chassis is 0.8 mm, no matter what material is placed between said distance. However, a more strict interpretation (and probably the correct one) is that the minimum distance is not less than 3 mm.