Hi Folks
Is this not just the old UL/CSA (UL 1457/1950 etc) test to simulate a 120V
power line falling onto the external POTS (etc)cable?
In which case the test generator would be as per the relevant UL/CSA specs,
and from memory that is similar to what has been suggested by Ken Javor or
Don Borowski.
This test was carried out because in North Americal most telephone cables
and power cables are strung on poles - and the lines contact each other when
the poles get knocked down by the awful weather (and/or awful drivers in
some cases!) they often get in many states (Thank goodness I live in the UK
- we don't get as much weather like that!)
BTW, IMHO:
a) Instead of a default of 120V, the test should specify the default to be
application of the maximum nominal supply voltage of the equipment being
tested, since that is likely to represent more closely the supply voltage on
the power poles where the equipment is to be installed. [i.e. it would be
120V for N. America, but it would be 230V for Europe - and so on].
b) Even the latter does not address the problem that many overhead power
distribution cables are 3-phase - so the test voltage should be the maximum
phase-to-phase voltage in question.
However, it has to said that the above changes would not go down well with
suppliers of existing certified equipment - and I have no history to prove
that the existing test is anything but adequate.
Does anyone else know of "real world" problems that this test does not
cover?
John Allen
Technical Consultant
Electromagnetics, Safety and Reliability Group
ERA Technology Ltd
Cleeve Rd
Leatherhead
Surrey KT22 7SA
Tel: +44 (0) 1372-367025 (Direct)
+44 (0) 1372-367000 (Switchboard)
Fax: +44 (0) 1372-367102 (Fax)
-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: 11 December 2002 22:19
To: [email protected]
Subject: Re: TNV Test Generator
Am I missing something, or can you not just take a low impedance source of
120 VAC and simply add an external 1200 resistor in series with its output?
Don Borowski
Schweitzer Engineer Labs
Pullman, WA
FastWave <[email protected]>@majordomo.ieee.org on 12/11/2002 12:55:45 PM
Please respond to FastWave <[email protected]>
Sent by: [email protected]
To: "'[email protected]'" <[email protected]>
cc:
Subject: TNV Test Generator
Telecom - Product Safety Question:
I am looking for a "test generator" per clause 2.3.5 of IEC60950 = "a test
generator is used that provides 120 V +/- 2 VAC at 50 or 60 Hz and has an
internal impedance of 1200 ohms +/- 2%". Anybody have any input on a source
to buy or a method to build such a device. It's the internal impedance
aspect that's throwing me for a loop.
Thanks for your time and input,
Bill Bisenius
ED&D
[email protected] <mailto:[email protected]>
North Carolina - the natural disaster capital of the U.S. - last week's ice
storm left us all without power, heat, or phones for several days (during
30
degree weather). Come to North Carolina and have your house smashed by
falling ice covered trees (or hurricanes in the summer).
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