[802.3_PDCC] Changing resistance due to temperature rise
Dear all
I have a question I would like to discuss during one of the next PDCC meetings:
Let us assume a procedure as follows:
Initiale situation: SPE-Link has 9 Ohm DC loop resistance
SPE device, which requires power class 15 is connected over the cabling to the switch and therefore to the power source.
Due to relativ resistance (ohm per meter) and installation environment conditions the cabling is getting hotter and therefore the DC loop resistance is rising to 10 Ohm.
What will happen?
- Will the power source automatically switch to the next lower power class?
- Will the device send information to the switch that the power class is not as expected?
- After a while, the cabling has cooled down again and power class 15 would be possible again. Will the power source switch on? For how many times this cycle will be repeated? When will the electronics give up and report an error?
These points are important as it might impact the way cabling has to be defined to avoid certain unwanted behaviour.
Best regards
Peter
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