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Steve, there was some discussion about 2
pair cables and how you can’t assume that the extra copper is there to
help dissipate the heat – for af. There is a lot of work yet to do. - From:
owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Steve Robbins Regarding the issue of cable heating, I
have a concern about Jo Wallings analysis. In his supporting document,
"walling_2_0905.pdf" the last sentence in the second paragraph states
"...under the assumption that all pairs in all cables are energized with
the same current." This is a valid assumption for PoE Plus,
since it appears very likely that we'll use a 4-pair system.
But Jo's assumption is invalid for 802.3af since only half of the pairs
are carrying current. So I think Jo overestimated the heat
dissipation in the cables (for 802.3af) by a factor of 2. |