Lennart:
I believe this does need some clarification.
I'm confused by the phrase "for a duration of at least TLIM".
Historically going back to 802.3at, Tlim is a variable. Given this, the phrase should be
"for a duration of at least TLIM_min".
Looking at table 145-16, Tlim is shown as a minimum with no maximum. Does that make it a fixed value ?? Looking at Figures 145-23,24, there is a Tlim_min on the time axis. So that supports that it is still a variable.
In my way of thinking, Tlim is the amount of time that a PSE tolerates a state of current limiting and/or foldback prior to removing power. It varies by PSE and by other factors. Tlim_min is the hard requirement.
I'm also concerned about the phrase "...and is required to shutdown before TLIM". In 802.3at, Tlim_max was not defined in the power supply table but was definitely conveyed by the current template as 75 msec, or Tcut_max. So in 802.3at, you could say "...and is required to shutdown before Tcut_max".
In 802.3bt, the current templates allow that currents higher than Ilim-2P_min could run forever. Does that mean a PSE could hypothetically go into current limiting (> Ilim_min) and stay that way indefinitely? No doubt a weird case, but this would not have been possible in 802.3at.
Regards,
Pete J
Sifos
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