High Voltage PCB Design

this may be a better online calculator for what you're doing:

Well, I may not have been clear, but it is not spacing in the X direction, it's i Z (from one layer to another layer, through the prepeg)

Cheers

Klaus

I think it's much more, say 8mm. But it depends upon some factors. We usually run N on the top layer and L on the bottom, etc. THis way only the component lead spacing matters and slots can be used betweend them. You can also use slots if the traces are on the same layer, but that makes for some floppy boards.

Cheers

Naturally I don't have UL-whatever in front of me, but I believe that's fine.

There's no such thing as creepage inside a solid material, and clearance is whatever it comes to based on dielectric plus safety factor. You will have some difference if it's fresh-from-the-utility or if it's been over some MOVs or whatever (transient limited).

Where you take a big hit is on the surface, either with the potential for pinholes in the soldermask coating, or with none at all, and the through-air creepage over a potentially-contamination-prone surface.

Tim

-- Seven Transistor Labs Electrical Engineering Consultation Website:

But it also says "The standard prepreg FR4 type multilayer is not suited to medium or high voltage work."

I would discuss this with the PCB manufacturer and get something in writing. Because what you need is a rating for a working voltage and not just a breakdown voltage or dielectric strength.

their other page shows that 0.3mm might be ok-ish depending on your peak voltage:

It's just a website on the internet, so use with caution. 480VAC even at

Here in the US, 480 is in the "arc flash" range where all equipment now gets huge warning stickers, and people that touch the equipment wear beekeeper outfits. I'm going to assume your equipment runs at lower power levels if a fractions of a mm are an issue.

I think it's very bad idea..

The reason I say that is, I work with in a semi industrial environment and if this 480VAC is from this type of environment, you're board should be prepared to handle at least 1200V and have some clamp protection below that with some small reactor maybe to handle the short spurs.

That's my opinion, I've seen a many of cheaply made electronics putting things on the hairy edge like that with blown holes and char around them from break down.

Of course if you're the type that believes in built in obsolescence than you're all set!

Jamie

Technically, "medium" starts at 600V, though the arc flash hazard is no less significant at 480.

Certainly, you can't go wrong if you get everything in writing (and also look up the full standards)!

Tim

On a sunny day (Tue, 26 Aug 2014 21:09:20 -0500) it happened "Tim Williams" wrote in :

The writing may not prevent your ciruit from going up in flames, or somebody with it. I think that distance is way too small. I may be oldfashioned, but why not run insulated wires..

Too many peeseebees Too many lawyers

I once had that same exact question come up. Best source for me was the PCB suppliers themselves. Ask Rogers Field Engineer, or their tech service. From memory, can't remember the answer. ;(

But I do remember I was surprised at how large the gradient could be.

I have posted a request at the PCB supplier. Will post back here when I get the data

Cheers

Klaus

Look forward to that! Also, Someone else made the excellent suggestion of designing enough margin to include expected noise on your AC mains lines. There are specs for 'expected' noise on the lines published by IEEE PSES-EMC group [I think], from memory the voltages get into the 2kV to 3kV ranges for milliseconds. If you can't find the information, or don't have access to that group, let me know.

Nice link. Thanks.

If you intend to design something for 480 Vac (delta), I guess you should make your design compatible with at least 230/400 Vac wye/delta in which at least 1500/2500 Vdc separation is required. I haven't recently checked, what 690 Vac delta will actually require in PCB track separation..

That was distinctly implied at worst,and clearly stated at best. I use the same "specs" for trace spacing on surface as top-to-bottom. Very conservative.