Hi Timothy,
Typically the term 'High Voltage' has a definition but it's different for
each agency that monitors safety. If you specify to which agency you are
trying to get approval from , the definition is easier to ascertain.
Insulation Break down happens when the voltage finds an ionic path across
the insulator that is it's voltage barrier and conducts an arc to it's
return path conductor over that surface or through air.
IPC's definition for the application of acceptable measling is somewhat
vague and general... probably because no single set of terms can describe
the acceptable condition for every given configuration of voltage, material,
coating, etc...
In my work with UL and VDE we had a definition that said that any voltage
above 48 V whether AC or DC ... was considered High Voltage. All circuits
that operated at 48V or below came under the SELV rules. (Safety Extra Low
Voltage)
The voltages above 48 Volts had specific safety spacings between the human
user and the voltage to protect against Electric Shock hazard and between
primary circuits to prevent fire hazard. The higher the voltage the larger
the spacing. These spacings were large enough to account for the presence of
contaminants on the surface of the board and still have some margin for
error. Not all agencies have the same rules.
I hope that helps clear up the muddy waters a little...
Bill Brooks
Senior PCB Designer - [log in to unmask]
Zoneworx, Inc.
40925 County Center Drive, STE 200
Temecula, CA 92591
http://www.zoneworx.com
Tel: (909) 296-1226 x 1037
Co-Director / Education Officer / Webmaster
for the San Diego Chapter of the IPC Designers Council
http://www.ipc.org/SanDiego/index.html
http://home.fda.net/bbrooks/pca/
-----Original Message-----
From: Timothy Reeves [mailto:[log in to unmask]]
Sent: Wednesday, August 23, 2000 10:09 AM
To: [log in to unmask]
Subject: Re: [TN] Measling vs. Definition of High Voltage
I asked the same question not too long ago on this venerable list...the
answer that came out of it was that it's NOT defined anywhere.
No one would say 5V is high voltage, and no one would say 2000V isn't, but
where's the precise boundary? No standard. I suppose it warrants some study.
Timothy Reeves
QA Manager/Process Engineer
ECD Circuit Board Division
13626 S. Freeman Road
Mulino, OR 97042
(800) 228-8198 Fax (503) 829-5482
-----Original Message-----
From: Wanchai Charoendee [mailto:[log in to unmask]]
Sent: Tuesday, August 22, 2000 10:17 AM
Subject: Measling vs Definition of High Voltage
According to IPC-A-600A rev. F "Measling is acceptable for class 1,2,3
except high voltage application". May I learn the definition of 'high
voltage ? Thank.
Rgds,
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
|
