[SI-LIST] Re: 48V power distribution
- From: "Salkow, Steven" <steven.salkow@xxxxxxxx>
- To: jackmurphy@xxxxxxxxxxxx, weirsp@xxxxxxxxxx, tcuratolo@xxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Tue, 19 Oct 2004 10:46:40 -0700
Hey Steve
If your making your equipment for export to Europe you will need to meet
the requiremnets of IPC.
See http://dc.ipc.org/resources/tools.htm
Clearance Distance
The shortest distance (through air) separating two live conductors or
circuit components. See Creepage Distance.
Creepage Distance
The shortest distance between two conductors (typically, one primary,
one secondary).
On this site find:
This program is intended to serve as a guide to the manipulation of data
that supports the concepts and methodology for developing surface mount
land patterns that are identified in IPC-SM-782, "Surface Mount Design
and Land Pattern Standard".
Steve Salkow
Lockheed Martin
3200 Zanker Road
San Jose, CA 95134
(408) 473-4058 (san Jose)
(408) 742-4162 (Sunnyvale)
steven.salkow@xxxxxxxx
salkow@xxxxxxxxxxxx
(925) 462-1075 Home
(925-) 487-5946 Cell
(408) 468-7271 Numeric Pager
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Murphy Jack-MGI2488
Sent: Tuesday, October 19, 2004 10:30 AM
To: 'weirsp@xxxxxxxxxx'; tcuratolo@xxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: 48V power distribution
Steve,
The low voltage safety limit is actually >60Vdc or >42.4Vpeak. Under
those limits the circuit is considered SELV and spacings do not apply.
For centralized DC power inputs, UL requires a 500Vac (707Vdc) hipot
test between 48Vdc/RET and chassis to verify isolation. We make CO-type
equipment powered via a -48Vdc centralized DC power source and we use
UL60950-1 for Product Safety.
A 48Vdc battery power system has a float up to 60Vdc which is still
under the SELV limit.
The National Electric Code has DC power source limitations (voltage vs
current) that they classify Class 2 or 3. I'll admit that I'm not very
familiar with the NEC.
Jack Murphy
SR Compliance Engineer
Motorola BCS
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of steve weir
Sent: Tuesday, October 19, 2004 1:06 PM
To: tcuratolo@xxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: 48V power distribution
Tom, the biggest issue is that 48V exceeds the 42V low-voltage safety
limit
and so requires substantially greater clearances. A 24V system is under
that limit and does not face the same problem. 48V also changes the
dynamics of available semiconductors. 12V systems and to a certain
extent,
24V systems can leverage the super low on resistance and low capacitance
FETs and diodes. The last issue is one of magnetics and practical
form-factors. Given you work for Vicor, you should be pretty familiar
with
those and how taller primary to output ratios aggravate same.
Regards,
Steve
At 02:04 PM 10/19/2004 +0000, tompegbel wrote:
>Is there a good resource/document for addressing the concerns in
>bussing 48V power in a multilayer board? The recently popular 12V or
>lower intermediate bus approach has limitations as voltages get lower
>and current gets higher. There appears to be new approaches of using a
>higher bus voltage (24V or 48V) for distribution since this was
>explored in the 80's with the advent of distributed power and now more
>recently with VoIP type designs. Any assistance appreciated
>
>
>
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