Power Over Ethernet Interoperability Guide

Power Estimates for N-Pair Power Delivery

In Figs. 13.2 and 13.3, we do some simple calculations for voltage drop and power reaching the PD, and also the cable losses. Note that we have also done this for “efficient PoE” where we do not double the current for four-pair operation as in UPOE, but keep IEEEcompliant currents (Type 1 = 0.35 A; Type 2 = 0.6 A), but use four pairs to reduce losses. The key results of the figures are summarized in Table 13.2. In the table we have only quoted the results for max allowed current per strand, which is 0.175 A/strand for AWG 26 (CAT3) and 0.3 A/strand for AWG 24 (CAT5e). In other words, since the AT standard says we can pass 0.6 A through two pairs, we get 0.3 A per strand—there are two strands for the ...