High Voltage PCB Design

[Klaus Kragelund]

Hi

I have an application with a TG150 rated PCB board

We are running mains voltage of 480Vac on two adjecent layers on the PCB with 1mm distance between the layers

However, I would like to know what the minimum distance which would be accepted without long term problems (this is from mains phase to phase, so not safety related, which would normally be 1mm solid)

I found this link, which has good info:

http://www.magazines007.com/pdf/High-Voltage-PCDesign.pdf

On page 16 it details 150V/mil (6000V/mm)

So are we in the clear using 480Vac with say 0.3mm distance?

Thanks

Klaus

[Cydrome Leader]

480V mains power with 0.3mm spacing sounds like a really really bad idea.

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

http://www.smps.us/pcbtracespacing.html

[Klaus Kragelund]

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

[Martin Riddle]

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

[Tim Williams]

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: http://seventransistorlabs.com

"Klaus Kragelund" <klau...@hotmail.com> wrote in message
news:d3742f5a-ab65-41b5...@googlegroups.com...

[Joerg]

Klaus Kragelund wrote:
> Hi
>
> I have an application with a TG150 rated PCB board
>
> We are running mains voltage of 480Vac on two adjecent layers on the
> PCB with 1mm distance between the layers
>
> However, I would like to know what the minimum distance which would
> be accepted without long term problems (this is from mains phase to
> phase, so not safety related, which would normally be 1mm solid)
>
> I found this link, which has good info:
>
> http://www.magazines007.com/pdf/High-Voltage-PCDesign.pdf
>
> On page 16 it details 150V/mil (6000V/mm)
>

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

> So are we in the clear using 480Vac with say 0.3mm distance?
>

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.

--
Regards, Joerg

http://www.analogconsultants.com/

[Cydrome Leader]

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

http://www.smpspowersupply.com/ipc2221pcbclearance.html

It's just a website on the internet, so use with caution. 480VAC even at
50 or 60Hz is beyond the range where corona problems can start.

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.

[Maynard A. Philbrook Jr.]

In article <d3742f5a-ab65-41b5...@googlegroups.com>,
klau...@hotmail.com says...

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

[Tim Williams]

"Joerg" <ne...@analogconsultants.com> wrote in message
news:c64nn5...@mid.individual.net...

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

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)!

[Jan Panteltje]

On a sunny day (Tue, 26 Aug 2014 21:09:20 -0500) it happened "Tim Williams"
<tmor...@charter.net> wrote in <ltjek0$rcb$1...@dont-email.me>:

>"Joerg" <ne...@analogconsultants.com> wrote in message
>news:c64nn5...@mid.individual.net...
>> But it also says "The standard prepreg FR4 type multilayer is
>> not suited to medium or high voltage work."
>
>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

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

[RobertMacy]

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.

[Klaus Kragelund]

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

Cheers

Klaus

[RobertMacy]

On Wed, 27 Aug 2014 06:22:36 -0700, Klaus Kragelund
<klau...@hotmail.com> wrote:

>> ...snip...

> 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.

[John Larkin]

On Tue, 26 Aug 2014 12:49:40 -0700 (PDT), Klaus Kragelund
<klau...@hotmail.com> wrote:

>Hi
>
>I have an application with a TG150 rated PCB board
>
>We are running mains voltage of 480Vac on two adjecent layers on the PCB with 1mm distance between the layers
>
>However, I would like to know what the minimum distance which would be accepted without long term problems (this is from mains phase to phase, so not safety related, which would normally be 1mm solid)
>
>I found this link, which has good info:
>
>http://www.magazines007.com/pdf/High-Voltage-PCDesign.pdf
>

Nice link. Thanks.

[upsid...@downunder.com]

On Tue, 26 Aug 2014 12:49:40 -0700 (PDT), Klaus Kragelund
<klau...@hotmail.com> wrote:

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..

[Robert Baer]

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.