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Hi Team
I am trying to design a PD power supply, armed with
IEEE802.3af/D4.0 and EN60950-1:2001. In particular, I am struggling with the
requirements of isolation between the Ethernet cable and my low voltage
circuitry. Can I trouble someone for assistance?
1 The 802.3af spec (section
33.4.1, Isolation) refers to IEC 60950 section 5.3.2. My copy of EN60950
section 5.3.2 is about fault conditions for motors. Does the 802.3af spec mean
section 5.2.2? Or does EN60950 differ from IEC60950?
2 I am new to EN60950. I had hoped for guidance in the 802.3af spec on
issues such as creepage and clearance distances, types of insulation
etc. It appears that I may need to know whether my PSU is an SELV,
TNV-1, TNV-2 or TNV-3; whether I am working under Pollution Degrees 1, 2 or
3; what my Working Voltage is; what class of insulation I need; and so forth.
The spec seems to say that the 802.3af power is neither an AC Mains Supply nor a
DC Main Supply (since power is through the Telecommunications Network wiring).
Help! Can someone who has worked through this provide some
pointers?
I know you don't want to change the spec at this
stage, but are you sure there is enough information in the spec to answer these
questions and allow compliant PD equipment to be designed?
Many Thanks
Regards -
Charles Palmer Technical Director, DSP Design Ltd
email: charles@xxxxxxxxxxxxx 7 Tapton Park Innovation Centre, Brimington Rd, Chesterfield S41 0TZ, UK ph: +44 (0) 1246 545 918 |