The power supply may simply have a condition of acceptability that
requires the end user to install it into a suitable fire enclosure. If the
power supply is going to be installed into a fire enclosure in the end use
there is no requirement for two fire enclosures.
The C of A's get overlooked a lot. Particularly with regards to
airflow. Often the power supply not meet the temperature requirements
without additional airflow not provided by the manufacturer and many an end
user has been surprised to find out that they have to add the airflow across
the supply.
Gary
-----Original Message-----
From: Ing. Gert Gremmen [mailto:cet...@cetest.nl]
Sent: Sunday, September 26, 1999 12:53 AM
To: duncan.ho...@snellwilcox.com; emc-p...@majordomo.ieee.org
Subject: RE: LCD Displays
Importance: High
Hello Duncan and group,
If your equipment is in the scope of EN 60950 (IEC 60950) or UL 950,
than it depends of the power source feeding it
The matters around FIRE ENCLOSURES are dealt with in paragraph 4.4.5
No Fire enclosure required for
Par 4.4.5.2 3th components in a SECONDARY CIRCUIT supplied by a
LIMITED POWER SOURCE and
mounted on a V-1 Class PCB
...
A LIMITED POWER SOURCE (2.11) is the mains power supply secondary supplying
your circuit when it's power
is limited by an inherent way of protection (fuse) and less then 250 VA or
protected by impedance and less then 100 VA. Some voltage and other
restrictions exist.
This power supply NEEDS the use of an ISOLATING TRANSFORMER.
This implicates that the full primary circuit must be contained into a FIRE
ENCLOSURE (4.4.4.1)
because the clause of 4.4.5.2. needs the ISOLATING TRANSFORMER (which is not
available in the primary)
The only parts that are fed by mains and need no FIRE ENCLOSURE are a MOTOR
or WIRING
This is why SMPS in ITE need to be completely encapsulated and open frame
SMPS are not allowed.
Nevertheless, many SMPS manuf's label their open frame supplies as 950
compliant. They can't ,unless
you are prepared to change your entire ITE into a compliant FIRE ENCLOSURE.
This is a major pitfall in most ITE equipment in our test house !!
The exact formulation is more complex , so read the stuff.
Regards,
Gert Gremmen Ing.
== Ce-test, Qualified testing ==
Consultants in EMC, Electrical safety and Telecommunication
Compliance tests for European standards and ce-marking
Member of NEC/IEC voting committee for EMC.
Our Web presence: http://www.cetest.nl
List of current harmonized standards http://www.cetest.nl/emc-harm.htm
15 great tips for the EMC-designer http://www.cetest.nl/features01.htm
-----Original Message-----
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of
duncan.ho...@snellwilcox.com
Sent: vrijdag 24 september 1999 19:23
To: emc-p...@majordomo.ieee.org
Subject: LCD Displays
I have a product that has an LCD display with an Inverter that operates at
100Khz 2KV and I believe is capable of supplying 6.5mA The question is does
it
require a fire enclosure?
If it does what are the requirements for the flamability of the screen and
any
plastic protective covers fitted to it. The screen is quite large, about the
size of a laptop PC screen. Perhaps some laptop PC manufacturers might have
some
ideas? are there any other things I must consider when using such a device
apart
from, obviously, insulation of the HT.
Regards,
Duncan.
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