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I would question the 2mA margin. For an Icon_unb_2P at 935mA, 2mA margin is 0.2%.
Effectively, if a PSE is configured to allow 937mA when the worst case valid possible pairset current is 935mA, that puts a lot of burden on the measurement of PSE performance to be super accurate and consistent between different testing setups. So I would hope to see a bit more margin for that reason alone, if no other reasons. Maybe 5 mA ?
From: Lennart Yseboodt [mailto:lennartyseboodt@xxxxxxxxx]
I see three issues raised in your review:
1) Incorrect description text. ==> Has been updated, see v103.
2) "How to calculate ICon-2P" ==> I will have a presentation to explain how this works, there seems to be confusion around this.
3) The amount of margin needed between ICon-2P-unb and IUnbalance-2P.
If, and only if, we are all 100% sure that the model used to calculate the values of ICon-2P-unb reflects what can be achieved by real implementations then no additional margin is needed.
We're in the process of checking if that is true.
If we decide no additional margin is needed, we can replace item 5a by an equation as you suggest.
On Sat, Aug 26, 2017 at 4:38 PM, Yair Darshan <YDarshan@xxxxxxxxxxxxx> wrote:
Hi Lennart and all,
You want to define Icon-2P_unb as a maximum value which is the correct approach and
To define Iunbalance-2P as the minimum current that the PSE should support which is also correct.
This is a simple approach that don’t create mass in our work so far for unbalance requirements.
Please show how you can calculate Icon-2P now. You will see that it is impossible. Using my proposal in (1) will bring the issue back to one problem only that can be solve by defining how to calculate Icon-2P-other.
Icon-2P_unb item 5: “Pairset current for PSE and PD due to unbalance per the assigned Class (for single-signature PDs)”
Table 145-16 item 5a: “Supported pairset current including unbalance effect per the assigned Class (for single-signature PDs)”
IUnbalance-2Pat Equation 145-8: is the current a PSE is able to source on a pairset due to unbalance as defined in Table 145–16
Not clear distinctions for the difference between all 3.
I’m afraid I may not be understanding what you are trying to say (or else you changed wording without actually meaning to) –
You make a distinction in your wording, which is either unintentional, or the meaning is obscure:
Icon-2P-unb max for the PSE and PD, item 5 in the table is: “Pairset current for PSE and PD due to unbalance”, and
Iunbalance-2P min that the PSE must support, in item 5a is: “pairset current including unbalance effect”.
Then, in 126.96.36.199, you specify the other language for Iunbalance: “is the current a PSE is able to source on a pairset due to unbalance as defined in Table 145–16”
You changed the Icon-2P-unb max language FROM “pairset current including unbalance effect” TO “due to unbalance”, which would ordinarily mean “the component of the current due to unbalance (excluding the nominal current)” to me (and I expect most readers). If you are trying to communicate something with this change of language, I don’t know what it is, and I suggest we need another try at it. Otherwise I think that:
“Pairset current for PSE and PD
I would also suggest the same language in 188.8.131.52.
On a different note, you’ve gone to this trouble of defining a new, separate parameter Iunbalance to be the current supported, only so you can compute Icon2P. why not just put Icon2P in the table appropriately?
It might look a little messier in the table, because it will have a min (Icon - IPort-2P-other; (whatever the value of Iunbalance-2P is for that class )) in it, but for the reader, it would all be in one place then, and be simpler to follow.
And, you wouldn’t have to define new values…
I copy-pasted the table and forgot to update the name in the second table. Sorry about the confusion.
Attached a new version with correct naming.
Yair - the intention is twofold
a) make appropriate parameters for the 3 requirements
b) create margin between maximum allowed unbalance and what the PSE needs to support
This goes beyond adding a few mA. I've rounded off to the nearest 100mA multiple, but we can also pick something else.
On Fri, Aug 25, 2017 at 5:46 PM, Yair Darshan <YDarshan@xxxxxxxxxxxxx> wrote: