Since this shutdown method might be considered normal operation, have
you considered the consequences
of rating your wiring, switches, thermal contactor etc. for the short
circuit current capacity? A non-autoreset
thermal switch (thermal fuse) would be a much better solution.
Bob Johnson
ITE
Note that the code permits EPO switches to be implemented with an
orderly shutdown process.
The NFPA 50 (NEC) clause 685 is used. It requires extra process
documentation and approval, but
you can do such things as delay shutdown during software save routines,
delay automatic shutdown to
permit
You are referring to a Shunt Trip circuit breaker. These circuit breakers
have an additional mechanism that will trip the actuator. The shunt trip
mechanism is activated by a switch closure. It does not degrade the normal
trip mechanism or contacts of the circuit breaker. The shunt trip
I'll second what Bill said.
And don't forget safety testing.
Best regards,
Clif Brick
Clifton Brick
Compliance, Safety and Patent Engineer
Invisible Technologies, Inc.
1000 Fuller Drive
Garrett, IN 46738
Phone 260-467-5139
Fax 260-467-5103
_
From: emc-p...@ieee.org
Instead of shorting the AC Mains, have you considered using a breaker
with a trip coil? We used one in a product where as a safety measure, if
something bad happened, we wanted to cut power to the entire machine.
All we had to do is short out a set of contacts which powered up the
trip coil to
Gregory,
You should recommend thermal overtemp cutouts in each power lead (if AC
mains) that open upon overtemp rather than closing upon overtemp, with
reference to IEC 60950-1, Clause 4.3.7 (Heating elements in earthed
equipment).
Shorting the mains is probably going to annoy someone, if not
David,
Full testing to the applicable Harmonized Standards of the RTTE Directive,
along with a Technical File is needed for compliance meeting the essential
requirements of that Directive. If partial testing is done (for valid reasons)
or Harmonized Standards are not/cannot be used, consult a
My advice would be to ask the guy concerned to find out the required
information to enable him to calculate how much energy he might have
to contain and then dissipate, both under 'normal' and under 'fault'
conditions (i.e. if his proposed circuit or something upstream of it
suffered a
I also replaced the shorted battery of my beard-clipper with a Radio Shack
ni-cad AA, soldering the wires directly to the battery. It has been working
fine for the last six years. Ni-cads don't like heat so you want to solder as
quickly as possible.
David
_
From: emc-p...@ieee.org
I am not aware of a specific standard prohibiting such a practice, but
agree whole heartedly that this is a bad idea. It is better to sense
the condition of concern, either directly or indirectly, and have an
electromechanical relay (or other device with air gap contacts,
depending on the
I tried to replace the batteries in my old Braun shaver (a pair of AA Ni-Cd)
but the whole board was dipped in some kind of epoxy and I broke the board in
half trying to get the batteries out. When I replaced the shaver I didn't get
the chance to check that the new shaver had accessible batteries
I have already done that. Twice. Had the same problem on an earlier model,
bought replacement batteries and did a remove and replace. It never worked
after that. This time I was just going to remove the batteries, based on the
replies to my original post.
From: Price, Ed ed.pr...@cubic.com
From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Thursday, October 05, 2006 10:49 AM
To: IEEE EMC Discussion Group
Subject: Re: end-of-life battery effects
Thanks to all who replied. It was indeed a pair of NiCd batteries. I am kind
of like Mr. Borowski, I hate to throw something
I highly recommend against placing a short circuit across the mains. The
only thing worse than shorting phase to phase is shorting a phase to
ground.
Circuit breakers are designed to protect from overloads, short circuits and
ground faults. However, the number of operations a circuit breaker
Thanks to all who replied. It was indeed a pair of NiCd batteries. I am
kind of like Mr. Borowski, I hate to throw something out that can be easily
fixed. I am going to remove the batteries and continue to use the device as
a mains-powered appliance.
-
This message is from the IEEE Product
Since the built-in protection device will trip at a current much lower than
what would trip the service panel breaker, can you do a high resistance
short that would not trip a service panel breaker but serve your purpose?
From: gmccl...@lexmark.com
Date: Thu, 5 Oct 2006 12:25:11 -0400
To:
I'm not sure of a standard, but I'm assuming that by shorting the mains
he wants the breaker to operate. Unless this is a hardwired circuit with
no possibility of other equipment being attached to this circuit your
customers aren't going to be real happy when your equipment fails and
it protects
Ken
Its time to ask Santa Claus for a new one I think. I would suspect the
battery current sense circuit is over driving because of a dead battery.
The charging circuit must be hardwired whether turned on or off. I'd
hate to break mine to figure it out.
Regards
Dan
-
This message is from the
Gentlemen,
I need your collective memory.
I have an engineer that wishes to design a protection mechanism to apply a
short circuit across the mains in order to open a protection device
upstream to stop an over-heating fault. The protection device would be in
the product, we are not talking about
In message
of1ea5f29a.4efbfdd8-on882571fe.005614f7-882571fe.00586...@selinc.com,
dated Thu, 5 Oct 2006, don_borow...@selinc.com writes
But then again, my (mains powered only) electric razor is 35 years old.
A new set of (inexpensive) brushes for the motor every 10 years or so
and it just keeps
Ken,
I agree with John's diagnosis of a shorted cell. If it's not damaged too
badly, a method I use is to blow the shorts out of the failed cell. I'll
charge a large capacitor to a fairly high voltage (12V) and apply it across
the shorted cell (not across the battery). Zap it a few times as
Ken-
Most likely the razor uses ni-cad cells. One of their common failure modes
is a short circuit. With one of the cells shorted, the voltage across the
string of cells decreases, and often the charge current increases. The
increased current will cause the still good cell(s) to get warmer. Often
In message c14a8bf1.452f5%ken.ja...@emccompliance.com, dated Thu, 5
Oct 2006, Ken Javor ken.ja...@emccompliance.com writes
Today the case was hot to the touch, and I disconnected it. What is
happening to the battery?
It is almost certainly an NiCd that has 'whiskered' and shorted out some
All,
This isn't a professional inquiry, but just curiosity. I have a rechargeable
electric razor whose battery over a year ago failed to hold a charge. I have
continued to use it as an ordinary mains-powered electric appliance, and I
leave it plugged in all the time. Lately it has begun to feel
Hi All,
Is full testing to applicable ETSI harmonized standards for radio products
under the RTTE Directive mandatory? Or is partial testing and manufacturer's
Declaration of Conformity sufficient?
Thanks in advance for any opinions
Regards
David Shidlowsky
Technical Writer
EMC Laboratory
ITL
Derek,
If the wall-wart is insulated, the cabling to AE provides the earth
reference. For UTP Ethernet the RS-232 gnd is the earth potential of
the system. For STP Ethernet it is a large ground loop with an RF
generator in the middle.
I suggest you send an e-mail to METI and ask themI have done this numerous
times and they have always answered within a week or two. They have been very
helpful..As a suggestion you must be very specific with your questions and
don't make the e-mail too long as it can muddy the
From: stuben...@ieee.org [mailto:stuben...@ieee.org]
Sent: Thursday, October 05, 2006 4:37 AM
To: 'EMC PSTC'
Subject: Celwave Isolator Specifications (off topic)
I've scoured the web and tried contacting Celwave/RFS/Ferrocom/Alcatel in an
attempt to locate the specifications/data sheet for the
HI All,
thanks for the great suggestions. I didn't get chance to work on this
yesterday too much, but hope to this evening ( USA time ).
Just to clarify, this is a small plastic box about the size of a
matchbox with 3 connections. Ethernet, RS 232, and low voltage dc from a
wall wart.
I did
Direct plug-in units will require DENAN approval and PSE marking. JET
provides some additional information on approvals and they use a power
supply for many of their examples.
http://www.jet.or.jp/en/guide_1.html
There are a number of test laboratories capable of DENAN testing and these
Hi Derek,
I've seen a couple of posts with good advice. I'm wondering if you've
already taken care of bonding the shield; and you're still having issues.
Forgive me for repeating your question...but I'm thinking out loud (which
is difficult for email :-)...for some reason when you just have the
I've scoured the web and tried contacting Celwave/RFS/Ferrocom/Alcatel in an
attempt to locate the specifications/data sheet for the Celwave Model
CD220-B isolator. Can anyone provide to me this information?
I apologize for this off-topic post, but figured there was a chance that
some of the
Hi all
I'm trying to understand the Japanees approval regulations, but I'm
confused. My product is a small wallplug type switch-mode PSU with an output
of 5 Vdc, 1A.
For electrical safety under List of Specified Electrical Appliances and
Materials 112 items (Category A) part 5; 1)(2)it is
Derek,
the reason for the observed effects is simple:
-1- when using a (foil?) shielded cable the shield of the cable is acting as
an antenna. The RF noise
is injected by coupling of internal circuits to the connector shield the RJ45
connector which is connected
to the cable shield
-2-
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