1. What is the correct method to test for a Limited Power source in
determining what enclosure is required?
The Isc limits must be met regardless of the load,
not only at 30a or 8a. You need to do sufficient
testing to satisfy yourself it will comply in general.
In this case you have demonstrated a failure.
2. If a fire enclosure was needed what is the minimum plastic
rating
i.e. 94V0, V1 or what?
94V-0 is not mentioned in the standard.
Requirements would be for 5-V, V-1 or
other requirements in clause 4.7.3.2
if a fire enclosure is required.
3. I cannot put a 5A fuse in the product, the lab says that the
overcurrent protective device must be outwith the non-fire enclosure in
order to stop the non compliant energy source entering the enclosure. Is
this correct?
Somewhat. The portion of the circuit not meeting the
requirement is the part which needs the enclosure.
Note that this does not mean the entire product.
You can provide a fire enclosure around a small entry
area and not include the rest of the product.
4. Similarly, I cannot use a resettable fuse in the product to meet
these requirements?
You may meet the requirements with fuse, PTC or other limiter.
5. Does the PTC used in the power supply need to meet the IEC
60730-1?
Not if you can assure the requirements relevant to the
application are met by your own testing. See clause 1.5.2.
Bob Johnson
ITE Safety
-----Original Message-----
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Alex McNeil
Sent: Friday, August 30, 2002 5:25 AM
To: 'emc-p...@majordomo.ieee.org'
Subject: EN60950-1 Sect 2.5 Limited Power sources
Hi group,
I have a query on the understanding of the above section. I thought I
fully
understood it until I used a different lab for Product Safety Compliance
testing (both accredited!).
We use a linear (basically a transformer with a PTC thermistor) class II
SELV O/P stand alone power supply rated 10Vac, 5A. One of the labs
tested
the O/P Isc with a direct application of the sc. The other lab tested
the
O/P Isc by applying a load of 8A. The results were therefore interpreted
differently.
Isc (direct) = 30A falling to 0A within 30secs. Considered a PASS (8A
for <
1min)
Isc (8A load) = 8A for > 2mins. Considered a FAIL (8A > 1min)
This has a crucial bearing on whether I need a fire enclosure or not for
my
all plastic enclosure!
1. What is the correct method to test for a Limited Power source in
determining what enclosure is required?
2. If a fire enclosure was needed what is the minimum plastic
rating
i.e. 94V0, V1 or what?
3. I cannot put a 5A fuse in the product, the lab says that the
overcurrent protective device must be outwith the non-fire enclosure in
order to stop the non compliant energy source entering the enclosure. Is
this correct?
4. Similarly, I cannot use a resettable fuse in the product to meet
these requirements?
5. Does the PTC used in the power supply need to meet the IEC
60730-1?
I would very much appreciate clarification on this matter.
THANKS!!
Kind Regards
Alex McNeil
Principal Engineer
Tel: +44 (0)131 479 8375
Fax: +44 (0)131 479 8321
email: alex.mcn...@ingenicofortronic.com
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