I have not seen many comments about the remarks of Mr. Lawler (remarks
copied at the end of this note). He raises an important point about
standards which have a major effect on product design and cost.
We see a proliferation of EMC standards coming from the IEC and
sometimes blindly adopted by CENELEC. For many reasons these new
standards and requirements are not in the best interest of the consumer
since they raise the cost of the product without really adding value.
In other words adding some of the EMC requirements has not resulted in a
better product. Some of the requirements have actually necessitated
that more EMC standards be generated. Harmonic limit requirements have
resulted in the generation of interharmonics so now we will have
interharmonic requirements in the near future.
It is time we pay attention to the standards makers and question why
there is a need for the new standard (In this case the IEC and CENELEC
in parallel.) We can comment on new standards to the US National
Committee through the EMC Advisory Committee. If a standard has a
problem we can report it to the advisory committee and if it has an
impact in industry the committee can write a new work proposal to make
it right. There are procedures in place to help industry to improve the
standards.
More activity and volunteers are needed to help in the standards
process.
Dave George
Unisys
----------
From: plaw...@west.net [SMTP:plaw...@west.net]
Sent: Monday, June 15, 1998 8:16 PM
To: emc-p...@majordomo.ieee.org; Harald Buchwald
Subject: IEC601-1-2 and Voltage dip/interrupt testing
IEC601-1-2 (Medical EMC requirements) has a section discussing
the
voltage dip and interrupt requirements. In the Committee Draft
dated
1998-03-06, it's section 36.202.5.
It says the test method in IEC61000-4-11 shall apply with
modifications, and goes on to detail them.
What caught my eye was modification 2:
"For equipment and/or systems having multiple voltage settings
for
power input, the test shall be performed at EACH RATED INPUT
VOLTAGE.
For equipment and/or systems having, for power input,
autoranging
voltage capability, the test shall be performed at the MINIMUM
RATED
INPUT VOLTAGE."
(emphasis added by me)
Our power supply products are typical wide-range units, with AC
input
voltage specifications of 90-264VAC, and would have little
problem
meeting the requirements at 230VAC. However, meeting voltage
dip and
interrupt requirements at 90VAC would require a redesign.
How did this 'all rated voltages' clause get in the spec? I was
under
the impression that all EMC testing was done at 230VAC, being
the
european norm?
--
Patrick Lawler
plaw...@west.net
