O'Reilly logo

Power Over Ethernet Interoperability Guide by Sanjaya Maniktala

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

“Imbalance” as Per PoE Standards
A certain “resistance imbalance” (or “unbalance”), creates a corresponding “current imbalance.” We need to know how they are connected in PoE specifically.
The previous PoE standard (802.3af) says in Section 33.2.8.12 titled “Current unbalance”:
The specification for IUNB in Table 33-5 shall apply to the current unbalance between the two conductors of a power pair over the current load range. The 10.5 mA value is based on a simulated output current unbalance of 3 percent.
In Annex 33E (informative), the AF standard implies that this 3 percent current unbalance is caused by a 3 percent resistance unbalance:
The 3 percent cabling resistance unbalance is specified for the ISO/IEC cabling channel illustrated ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required