[SI-LIST] Re: 48V power distribution

  • From: john <johndp@xxxxxxxx>
  • To: weirsp@xxxxxxxxxx
  • Date: Tue, 19 Oct 2004 22:01:36 +0100

To export to Euroupe you need to conform to EN60950 (for IT equipment), 
this has the same 60V or  42Vp-p limits,
the creepage and clearance distances are also set out in this standard.
See :-

http://www.ce-mag.com/ce-mag.com/archive/01/03/ProductSafety.html

for an overview. It is relatively straight foward to get approvals for 
US and Europe, Japan is a slightly trickier matter as the
SELV limits we discovered were lower.

Regards

John

steve weir wrote:

>Steve, yes I know of a company that did not pay attention to the more 
>stringent European standards and failed to maintain adequate creep 
>clearance on their -48V feeds, and that forced an expensive redesign of 
>entire chassis.
>
>Regards,
>
>
>Steve
>At 10:46 AM 10/19/2004 -0700, Salkow, Steven wrote:
>  
>
>>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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>
>
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