On Sat, 18 Oct 2008 17:12:48 -0700, Charlie Springer
<RAM@regnirps.com> wrote:
>On Sat, 18 Oct 2008 10:42:42 -0700, whit3rd wrote
>(in article
><7f356697-56f9-4e2b-9da1-60e1b27044cd@26g2000hsk.googlegroups.com>):
>
>>> I have to design a printed circuit board for a high-voltage environment.
>>> Hence, the "ground potential" of the board has to be on 4 kV.
>>
>> This is the same sort of problem as electron microscopes (and
>> even microwave ovens) have in driving the filament. The easy
>> solution is to box up a 6V battery and regulate down to 5V.
>> The commercial solution is a custom-made, tested, transformer
>> that safely holds off 4 kV. It's likely to be potted (embedded
>> in a blob of tar or silicone).
>>
>> You don't want any of the 4kV parts outside a shielded and
>> interlocked enclosure, of course...
>
>There are neon signs all over the place, often within reach of drunks
>........ ?
The output impedance and hence short circuit current of the HV supply
is also on issue. A 4 kV 1 mA should not be that dangerous :-), unless
of course if there is a large (stray) capacitance at the power supply
output, which could store a significant charge, which could cause a
nasty electric shock flowing through your body. For instance the CRT
25 kV anode connection has quite a significant capacitance.
There are miniature neon signs within windows advertising a product,
in which the leads or connections could be touched. The short circuit
current is so small that it does not do any harm.
Other typical examples would be simple ionizer with about two dozen
rectifiers and capacitors in a voltage multiplier chain, fed directly
from the 230 V mains. You could touch the output of the chain, but of
course it is a good idea to have a 1 megaohm at the output to limit
the current in case of the extremely rare situation that _all_
rectifiers and capacitors would fail and you would have 230 V mains at
the other end of the resistor.
We do not know if the original poster is using such high impedance HV
source, but in that case using a high isolation transformer to feed
the 5 V side, the transformer stray capacitance (perhaps less than 10
pF) may feed 50/60 Hz hum into the HV line.
Paul
Reply by legg●October 18, 20082008-10-18
On Fri, 17 Oct 2008 09:02:50 +0300, Paul Keinanen <keinanen@sci.fi>
wrote:
>On Thu, 16 Oct 2008 17:49:25 -0400, legg <legg@nospam.magma.ca> wrote:
>
>>
>>You haven't indicated the voltage and power requirement for this
>>housekeeping supply.
>>
>>At lower power levels, some simple self-constructed solutions are
>>possible.
>
>At very low power levels, just send optical power up on an optical
>fiber and the data down on an other fiber.
>
>This system is used on some high voltage measurement instruments
>hanging on an overhead high voltage line.
>
If the OP would care to respond with the actual requirements, we'd
know if this was a candidate.
RL
Reply by Charlie Springer●October 18, 20082008-10-18
On Sat, 18 Oct 2008 10:42:42 -0700, whit3rd wrote
(in article
<7f356697-56f9-4e2b-9da1-60e1b27044cd@26g2000hsk.googlegroups.com>):
>> I have to design a printed circuit board for a high-voltage environment.
>> Hence, the "ground potential" of the board has to be on 4 kV.
>
> This is the same sort of problem as electron microscopes (and
> even microwave ovens) have in driving the filament. The easy
> solution is to box up a 6V battery and regulate down to 5V.
> The commercial solution is a custom-made, tested, transformer
> that safely holds off 4 kV. It's likely to be potted (embedded
> in a blob of tar or silicone).
>
> You don't want any of the 4kV parts outside a shielded and
> interlocked enclosure, of course...
There are neon signs all over the place, often within reach of drunks
........ ?
-- Charlie Springer
Reply by whit3rd●October 18, 20082008-10-18
On Oct 15, 11:40=A0pm, "Saul Bernstein" <jiffyl...@freenet.de> wrote:
>
> I have to design a printed circuit board for a high-voltage environment.
> Hence, the "ground potential" of the board has to be on 4 kV.
This is the same sort of problem as electron microscopes (and
even microwave ovens) have in driving the filament. The easy
solution is to box up a 6V battery and regulate down to 5V.
The commercial solution is a custom-made, tested, transformer
that safely holds off 4 kV. It's likely to be potted (embedded
in a blob of tar or silicone).
You don't want any of the 4kV parts outside a shielded and
interlocked enclosure, of course...
Reply by Paul E. Bennett●October 18, 20082008-10-18
Saul Bernstein wrote:
> Hi,
>
> I have to design a printed circuit board for a high-voltage
> environment. Hence, the "ground potential" of the board has to be on 4
> kV. Du to the fact that the absolute potential values don't matter, one
> could say that the 2 kV are virtually my ground potential. The problem
> arises by reason of the power supply. I have to power my board with 5 V
> and for the mains adapter ground is really 0 V.
>
> Can someone think of a possibility to supply my board with a mains
> adapter (AC/DC 220V/5V) and translate between the two ground reference
> potentials?
>
> Thank you
>
> Saul
Yes this sort of thing can be done but you really should know what you
are doing in the high voltage areas when doing projects like this. Some
of the systems I work with have rails of 132kV DC (in the MW region) and
this takes very special handling and checking from the design through
the implementation to maintenance planning before we build such systems.
As many of the professional engineers here who would know this stuff and
know of the dangers it is hardly surprising you are not getting much
help without knowing your level of experience. It is an area that is at
such a level that if you have to ask then you shouldn't be doing this
without adequate oversight and supervision. The professionals will want
to know that you have that in place and by asking here it is obvious
that you probably haven't and it would be criminal for them to offer a
solution.
--
********************************************************************
Paul E. Bennett...............<email://Paul_E.Bennett@topmail.co.uk>
Forth based HIDECS Consultancy
Mob: +44 (0)7811-639972
Tel: +44 (0)1235-811095
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************
Reply by Charlie Springer●October 18, 20082008-10-18
On Wed, 15 Oct 2008 23:40:17 -0700, Saul Bernstein wrote
(in article <48f6e1b8$0$6569$9b4e6d93@newsspool4.arcor-online.net>):
> Hi,
>
> I have to design a printed circuit board for a high-voltage environment.
> Hence, the "ground potential" of the board has to be on 4 kV. Du to the fact
> that the absolute potential values don't matter, one could say that the 2 kV
> are virtually my ground potential. The problem arises by reason of the power
> supply. I have to power my board with 5 V and for the mains adapter ground
> is really 0 V.
>
> Can someone think of a possibility to supply my board with a mains adapter
> (AC/DC 220V/5V) and translate between the two ground reference potentials?
>
> Thank you
>
> Saul
How much power do you need? How about a couple of solar cells and a halogen
work light?
-- Charlie Springer
Reply by CBFalconer●October 17, 20082008-10-17
Paul Keinanen wrote:
> IanM <Invalid@totally.invalid> wrote:
>
>> Its a far cry from two minature PM DC motors coupled shaft to
>> shaft with a couple of feet of Perspex rod in between :-)
>
> At least this mechanical system can be scaled to quite large
> power levels :-)
>
> http://en.wikipedia.org/wiki/Lyon-Moutiers_DC_transmission_scheme
Highly sensitive to dust, thus needing continuous maintenance, IMO.
--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.
Reply by Paul Keinanen●October 17, 20082008-10-17
On Fri, 17 Oct 2008 14:24:43 +0100, IanM <Invalid@totally.invalid>
wrote:
>
>Its a far cry from two minature PM DC motors coupled shaft to shaft with
>a couple of feet of Perspex rod in between :-)
At least this mechanical system can be scaled to quite large power
levels :-)
http://en.wikipedia.org/wiki/Lyon-Moutiers_DC_transmission_scheme
Other low power isolated power transmission systems include feeding
acoustic vibrations into an isolating rod or using radio frequency
power transmission (after all the isolation distance required is only
a few meters).
Paul
Reply by MooseFET●October 17, 20082008-10-17
On Oct 15, 11:40=A0pm, "Saul Bernstein" <jiffyl...@freenet.de> wrote:
> Hi,
>
> I have to design a printed circuit board for a high-voltage environment.
> Hence, the "ground potential" of the board has to be on 4 kV. Du to the f=
act
> that the absolute potential values don't matter, one could say that the 2=
kV
> are virtually my ground potential. The problem arises by reason of the po=
wer
> supply. I have to power my board with 5 V and for the mains adapter groun=
d
> is really 0 V.
>
> Can someone think of a possibility to supply my board with a mains adapte=
r
> (AC/DC 220V/5V) and translate between the two ground reference potentials=
?
How about a battery?
At low powers and bad efficiencies, transformers to handle a 4KV
isolation is fairly easy. At bigger power levels or efficiencies
above 50% it gets harder fast.
What does this PCB have to do? How much power etc?
Does the PCB live inside a shield?
At low powers, the simplest design is to use an "air core" transformer
with the primary and secondaries tuned and loose coupling between then
because of the large clearance. The down side is that this tends to
radiate a lot of RF at your operating frequency.
Reply by CBFalconer●October 17, 20082008-10-17
Saul Bernstein wrote:
>
> thanks for your kind answers so far. To answer your question:
> The PCB won't be connected to anything other than the 4kV and
> the 220V mains.