Hi Folks
Kyle make a very valid and serious point in his last paragraph =
re-engineering of vendors' products.
CE Marking of a vendor's product is a minimum requirement - suitability
for the intended application in YOUR system is at least as important. This
means preparing an adquate purchasing specification - and demanding proof
that it has been met.
If you make this type of purchase regularly then it is probably worth
putting together a generic set of requirements which cover your customers
requirements. You might also need a set of internal design guidelines for
incorporating the purchased items into your own systems.
We get these problems all the time as we design AC mains-powered
communications/ITE fits for road/off-road vehicles (often using on-board
230V diesel generators). What is suitable for office use is rarely
suitable for these fits without a lot of additional work (shock mounting,
extra grounding, additional temperature/humidity control to name but a few
areas).
In particular, IEC/EN/UL 60950 equipment may well not be suitable for
rough environments as there is generally absolutely no environmental
testing involved in most evaluations. A couple of years ago we vibrated an
industrial PC (admitted for a long time!) and most of the large capacitors
in the PSU fell off the PCB's . Also, a large amount of aluminium (I am
English - that's how we spell it!) dust was caused by a capactor rubbing on
a heatsink, and this finished up all over the primary AC tracks on the
PCB's. It still worked but it was very dangerous!
It is thus very important to specify exactly what you want of the products
you buy - and to make any installations/usage limitations clear in the
documents you supply to your customers. Conditions of Acceptability again
(and again!).
Regards
John Allen
Thales Defence Communications
Bracknell, UK.
-Original Message-
From: Ehler, Kyle [mailto:keh...@lsil.com]
Sent: 02 August 2001 20:57
To: 'Rich Nute'; 'EMC and Safety list'
Subject: RE: Mains fusing
Thank You so much Rich, Patricia, Mike, Jim, Ed, et al;
Please do continue to contribute your wisdom to this forum.
I spoke with my LES engineer and good friend at UL. [a good friend at UL is
a handy thing!]
Someday I should expound on the usefulness of proper care and feeding of
your agency engineer..
In our discussions, I pointed out the grey area in 1950 2.6.2 2.7.4 [B]
related to the conditions
of applicability (PAG), and that this modular product is deployed in a rack
mount environment
where the mains cord is terminated in a polarized coupler (and disconnect
device) making it nearly
impossible to reverse the mains.
In addition, the rack mount cabinet provides mains distribution to this
module through
double side breakers. I built my case on these two items and believe I can
get an approval
upon review.
I'm told the remaining problem with this UPS is it fails 61000-4-5 in our
lab, although it
passes 801-5, and that it also fails conducted emissions when using QP-Avg
techniques.
I could be in for engineering a fire enclosure to contain wiring, coupler,
filter, suppressor,
and while in the area, a double side breaker -and of course, the attendant
investigative redo.
Normally, this would be good reason for vendor rejection, or at least a
public drubbing in this
forum, but we are committed for the short term to use this vendor's product
and I cannot afford
to risk any relationships -for now. The decision was never mine to make.
And now we are in a familiar loop where the lab is used to re-engineer a
vendor's product
that is CE marked. Doh!!
Statue today, pigeon yesterday...
Thanks again,
kyle
my words, my opinions/mania...etc.
-Original Message-
From: Rich Nute [ mailto:ri...@sdd.hp.com mailto:ri...@sdd.hp.com ]
Sent: Wednesday, August 01, 2001 4:30 PM
To: keh...@lsil.com
Cc: emc-p...@majordomo.ieee.org
Subject: Re: Mains fusing
Hi Kyle:
I have a new product that includes an off the shelf UPS that is rated
for
230V ac operation and has an internal single pole circuit breaker on the
mains inlet. We want to target this product world-wide. The UPS
presently
is CB and certified to EN60950 european only. For North America we want
it
to have UL1950, and to obtain this, UL is demanding the breaker be
double
pole.
This is an unusual situation.
On the one hand, the UPS, with single-pole overcurrent
protection, has a CB to EN 60950 for use in Europe where
most mains supply plug configurations are non-polar.
There is no control that the overcurrent protection will
be in the live conductor.
On the other hand, the UPS, with single-pole overcurrent
protection, is denied UL certification for use in the
North America where UL requires polarization of both
the UPS overcurrent protection and the mains supply plug
configuration. There is a reasonable control that the
overcurrent protection will be in the live conductor.
