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Re: safety

Title: safety
Ed, I think the idea of getting people that could give us guidance on the safety issues is an excellent idea.  I would hope that we would use that guidance to generally shape our thinking without calling out any of the safety specifications directly in our standard. 
Best regards,
Robert D. Love
President, LAN Connect Consultants
7105 Leveret Circle
Raleigh, NC 27615
Phone: 919 848-6773
Fax: 720 222-0900
email: rdlove@xxxxxxxx
----- Original Message -----
From: Walker, Ed
Sent: Friday, August 11, 2000 12:13 PM
Subject: safety

When testing a system UL will do abnormals.  On an offline power supply they will OPEN and SHORT EVERY COMPONENT on the design to test failure mechanisms.

Must not present to a user:

No dangerous smoke.
No dangerous voltages, 240VA power limits, SELV etc.
No traces on boards can vaporize.
If active failure such as lots of smoke and sparks, must not ignite cheese cloth placed in proximity to failure area.

There are lots more.

Regarding current protection: If a non UL approved device is used for the primary protection then a secondary means of protection is required. UL will disable the primary means of protection and rely on the secondary protection to work.  Example: standard Mosfet used for current limit will assume to be able to fail shorted. UL will place a wire across it then short the output. Supposing a secondary means is a PTC then this must not allow enough current to fail the system. UL approved/recognized active protection devices available which might negate the need for secondary protection. A UL approved current limit device that meets the tight tolerance and repetitive operation of 802.3 would be beneficial.

There are lots of areas in this 802.3 implementation that need a safety aspect. I suggest that the group contact UL and ask for a representative to become part of the group.


I see no way that a POWER system can be specified properly unless you bring in the safety agencies, UL, TUV, European (EN?), etc.