Factors contributing to the ΠPlacement factor

9 posts / 0 new
Last post
Anonymous (not verified)
Factors contributing to the ΠPlacement factor

In the Fides guide (Page 53), the Π Placement factor is defined by the items below:

Non-interface digital function

Interface digital function

Non-interface low level analog function

Interface low level analog function

Non-interface power analog function

Interface power analog function

The criterias of selection between the items are not very clear to me.

What is the difference between the low level analog function and the power analog function ? Is there a power threshold between the two items (10 W, 100W, 1000W) ?

What is the boundary between the interface and the non-interface ? Shall we consider the interface between the equipment functions ? Shall we consider the interface between the equipment and external systems only ? Are interface fonctions limited to protection items (transil, tranzorb...), fitering items (filters, coil, capacitors???), isolation means (optocouplers, transformers...), connectors...

Thanks

 

 

 

Edited by: tourtelier_d on 13/05/2014 - 11:26
Lambda
Re: Factors contributing to the ΠPlacement factor

The Pi_placement factor contribute to the calculation of the Pi_induced factor. The Pi_placement is one of the factor showing if the component is exposed to over stresses. It is well known that component at interfaces are more subjected to overstress. In the same way, the same component will be more exposed in a power function than in a digital function. The typical example of overstress affecting the interfaces is the unpluging of the equipement while powered.

What are the criteria to choose the Pi_placement ?

First of all, for a rapide study, the same Pi_placement may be given to a complete board. For a more detailled study, it is better to define the placement component by component.

Interface or non interface ?

Of course it depends of the whole system architecture.

An item should be placed in the "interface" category if it is subjected to a stronger exposure to overstress because of its position in the whole system.

You are right that :

- Item between the equipement and external systems are interfaces.

- Item at the interfaces are often (but not necessarily) protection items (transil, tranzorb...), filtering items (filters, coil, capacitors - yes), isolation means (optocouplers, transformers...).

Note that if your electronic board do have such protections, this is becauses external overstresses have been taken into account in the design. A well performed FMECA will probably shows that most failures of this protections are not mission critical. The operationnal reliability is therefore better despite the bigger amount of components.

Low level or power ?

From the FIDES Guide point of view, low level analog function are mainly discrete input/output, measurement, analogic logic and so on.

Power function are especially power supply or power transmission.

At first sight I would place the threshold around a current of 1A.

I hope these explanations will help you.

Lambda

Depret (not verified)
Re: Factors contributing to the ΠPlacement factor

Thank you for the quick answer. It is very helpfull.

lechaigne.fabien (not verified)
Re: Factors contributing to the ΠPlacement factor
Hi,

About the difference between "interface" and "non-interface", if our electronic board is into a system, with other electronic boards, but in a box which protect the whole, our system is always in "non-interafce" category?

Thank you for your help.

Fabien
Lambda
Re: Factors contributing to the ΠPlacement factor

Dear Fabien,

The interface notion has to be considered on an electrical point of view. Your box has probably electrical interfaces with a higher level system (at least power supply ?). Therefore, somes parts of your product have probably to be considered as "interfaces". For exemple, parts directly linked with external connectors are most often to be considered as "at the interface".

I hope that will help you...

Lambda

lechaigne.fabien (not verified)
Re: Factors contributing to the ΠPlacement factor
Dear Lambda,

I have got another question about Pi placement factor. There are two types of analog functions, low level or power. Does the component power determine the component category? My colleague, a power electronician, doesn′t understand exactly the difference between the two functions, and the way to find the category.

Thank you for your help.

Fabien
Lambda
Re: Factors contributing to the ΠPlacement factor

Your question is also the one that initiate this topic.

Look at my first post on this topic about Pi_placement.

lechaigne.fabien (not verified)
Re: Factors contributing to the ΠPlacement factor
I′m really sorry, I was convinced that the issue was not addressed.

Thank you very much for your help.

Fabien
Shiv Prasad
Regarding Phase 1 Application volatge of Capacitor

Hi,

Can I use FIDES for part count method reliability.

If Yes, then Applicaton voltage of ceramic cap will Zero?

Regards,

Shiv Prasad