Industrial Communication Guide

Power over Ethernet (PoE) If a component is supplied with power in addition to data transmis- sion, this is referred to as PoE (Power over Ethernet). PoE can es- sentially be realized in two different ways: the power is transmitted on unused wire pairs or else on wire pairs in addition to those al- ready being used for data transmission. The table shows the devel- opment of PoE. This shows that as the specification has advanced, the potential output transmitted has increased considerably (15.4 watts → 25.5 watts → 51 watts). 4PPoE means that all wire pairs are used to supply power.

In order to keep power loss to a minimum, the cross-sections of the wires have to be as large as possible. In addition, the connector contacts must have a special design for the purpose of electric arc protection, which can occur when the cable is unplugged when live. Otherwise there is a risk of the electric arc damaging the contacts to such an extent that data transmission is no longer fault-free.

Power over Ethernet

Standard

Release

Output 15,4 W 25,5 W

Amperage per wire pair

PoE

IEEE 802.3af IEEE 802.3at IEEE 802.3bt

2003 2009 2018

350 mA 600 mA

PoE+

Probably 51 W (possibly 71 W)

Probably 600 mA (possibly 960 mA)

4PPoE (bzw. „PPoE++“) A

52