Power over Ethernet (PoE) is a standard for sending data and power over a standard Ethernet cable to low wattage devices. In the IT industry, these devices are usually VoIP phones, security cameras and wireless access points. In the factory automation industry, low wattage motion control devices like motor drives and small integrated motors can also use this technology.
How does PoE work?
Currently, the most common PoE implementations work with standard Ethernet cable, the same kind found in offices and buildings around the world. There are eight wires in the Ethernet cable but only four of those are used to transmit data. PoE leverages the four unused wires in the Ethernet cable to transmit DC power.
Benefits
PoE devices can operate in remote, hard-to-reach and unpowered locations without the cost or hassle of running and installing new AC power lines. Ethernet cable is easier to install than electrical wiring and no special Ethernet wiring is required. Cat 5 to Cat 7A are approved for use with PoE, shielded or unshielded. PoE is also plug-and-play. Ethernet equipment automatically talks to each other to ensure PoE power is delivered only to devices that accept it.
PoE Terminology
A PoE installation includes two principle pieces of equipment. The Power Source Equipment (PSE) provides power to one or more PoE devices on the network. The Powered Devices (PD) are the PoE devices on the network that receive power from the PSE. Figure 1 outlines a typical installation where an Ethernet switch with PoE ports serves as the PSE. It provides power to an integrated motor (PD) with PoE functionality. The switch automatically detects that the integrated motor accepts PoE and provides power to it accordingly.
