The time domain measurements afternoon workshop topics
included:
1) Theory and description of the technique
2) Application of the technique
3) Demonstration of the technique in a semi-anechoic chamber
at ETS-Lindgren
The practical demonstration was especially illustrative as the
instructors showed that the technique not only is quite accurate
for the purpose, but will find those areas in a chamber where
absorber improvement is needed. This was demonstrated by
putting a piece of tin foil on one of the absorber tips and “finding” it via the validation technique. If this were a deficiency in
an absorber (or maybe a void in the absorber placement where
the metal wall of the chamber was exposed), corrective action
at that point could be made. Such an action may be increasing
the absorber efficiency or filling in the void in the absorbers.
Twenty-one students attended this full day workshop on
August 15.
All in all, the students were treated to two intense days of
training from widely recognized experts who in addition contributed to the text for the standards. C63® thanks again ETSLindgren which provided the meeting venue and use of their
semi-anechoic chamber and both UL and Agilent Technologies
for donating the lunches which were brought to the meeting
room to allow more time to be spent on the training.
The ANSI C63.4, ANSI C63.5 and time domain measurements workshops are planned to be given next year either
independently and/or just before the start of the 2010 IEEE
International Symposium on EMC in Ft. Lauderdale, Florida.
Organizers of the ANSI C63.5 and Time Domain Measurements Workshops included (from left): Dennis Camell of
NIST, Michael Foegelle of ETS-Lindgren, Greg Kiemel of
Northwest EMC, Mike Windler of UL, Janet O’Neil of
ETS-Lindgren, Jeff Poole of Agilent Technologies, and Don
Heirman of Don HEIRMAN Consultants.
Please check the C63® website – www.C63.org –
after January 2010 for more information about
scheduled ANSI C63® workshops in 2010.
EMC
Overview of IEEE Standard 1560:
Standard for Methods of Measurement
of Radio Frequency Power Line Interference
Filter in the Range of 100 Hz to 10 GHz
Kermit Phipps and Philip Keebler
Purpose of IEEE Standard 1560
Many commercial and industrial electrical environments contain equipment that is sensitive to radio-frequency (RF) interference. Theft detectors, digital sensors, and medical-telemetry
systems have all been known to malfunction in the presence of
RF interference that is conducted into such systems via their
attachment to the power source. EMI/RFI filters specified to
typical 60 and 100 dB attenuation levels are used in these and
many other applications to prevent unwanted signals on power
lines from disturbing the operation of these devices.
The main standard used to measure filter insertion loss
(synonymous for matched impedance attenuation, typically
50 ohms), is Mil-Std-220B. Mil-Std-220B was developed for
matched impedance communication systems to test mobile
radio filter suppression capacitors in 1952 (which in reality
matched impedances virtually never happens over a broad fre-
78
quency range between the filter output and the input to the
connected product). Hence, it has been labeled unrealistic for
mismatched power sources and load impedances found in almost all power applications.
Unfortunately, Mil-Std-220B, which is considered only a
face lifted version of its predecessor, Mil-Std 220A, has become
the industry norm, largely because of the lack of a viable alternative….until now. The problems associated with the test
methods defined in Mil-Std-220B have been known since it was
first used. In fact, the standard itself warns users about its limitations. Nevertheless, this standard has been referenced in other
standards and applied in thousands of applications throughout
the military and commercial industries to characterize powerline filters. Since then, other methods have been discussed and
developed that attempt to model “real world” attenuation by
requiring varying the power source and load impedance. As
–60
Attenuation (dB)
–70
MIL STD 220A
IEEE 1560
Method 10.5
1,000
10,000
100,000
Frequency (Hz)
Fig. 1. Generic 50 Amp Filter Measured Using Mil-Std220B and IEEE 1560 Method 10.5 with 30 Amp Loading.
Figure 1 illustrates, the Mil-Std-220B method gives a much
different expected value for attenuation than the more realistic
test method in clause 10.5 (Current Injection) found in IEEE
Standard 1560, which is the subject of this article.
To date, however, none of these measuring methods have
replaced Mil-Std-220B. IEEE 1560 still supports the continued use of the much-beleaguered matched impedance test as
the preferred choice for high frequency performance characterization and for quality assurance. Additionally, the usefulness
of IEEE 1560 is the fact that it addresses power quality issues and critical RF performance factors below 100 kHz
for realistic loads and sources which is not addressed in
Mil-Std-220B.
IEEE 1560 Working Group Efforts
The IEEE EMC Standards Development Committee, Technical
Committee - 4 (TC-4) – EMI Control, filter working group
has been engaged in evaluating filter standards and methods of
filter characterization for some time. These efforts were directed at bringing about standardized test methods for the effective measurement and specification of filters in a more realistic
use. After conducting a literature search and review of several
existing standards and methods, the following key areas were
chosen for review:
1) Effectiveness of LISNs (Line Impedance Stabilization Networks) below 100 kHz as a source impedance
2) Standardized AC source impedances
3) Standardized product load impedances and nonlinear load
characteristics
4) Waveshape quality measurements under nonlinear loading
5) AC filters used in DC applications
6) Matched impedance measurements above 10 MHz
7) Extended range from 100 Hz to 10 GHz techniques
8) Repeatable and standardized current injection test methods
The working group members considered all the possible
variables that previous standards did not recognize. Figure 2
illustrates such a case when two different loads are tested at the
same RMS value of current through the load and shows a difference due to inductor saturation.
As shown in Figure 2, the load characteristics are very important. These differences as well as others have resulted in
numerous cases of unnecessary costs (thousands of US dollars)
being spent to mitigate EMI for what might have been due to
misjudging the load characteristics.
–80
–90
–100
–110
–120
–130
1,000,000
–140
10,000
30 Amp Linear Load
30 Amp Nonlinear Load
100,000
1,000,000
Frequency (Hz)
10,000,000
Fig. 2. Measurement Results for Linear and Nonlinear
Loading with the Same RMS Current Value.
Attenuation (dB)
Attenuation (dB)
40
20
0
–20
–40
–60
–80
–100
–120
–140
–160
100
0
No Filter
–10
Filter Installed
Noise Source Off
–20
–30
–40
Desired Theft
–50
Detection Signal
–60
–70
-80
10,000
Frequency (Hz)
100,000
Fig. 3. Filter Gain Across the Attenuation Band.
Within IEEE 1560 is guideline for the use of s-parameter
data for designing power line filters. When the s-parameters
can be determined, a filter can be designed by using predictive
models as discussed in the standard’s annex to operate maximally in a specified environment, particularly where the source and
load impedances are not matched. The application of improved
test methods to better determine the performance of power-line
filters will also result in filter components that are less stressed
in the field, as well as a reduction in component failures caused
by overheating.
Figure 3 further illustrates a real world application gone
wrong in an attempt to mitigate an EMI problem with a department store theft detection system, where a gain of 10 dB
over the normal noise occurred instead of the expected 260
dB attenuation in the low pass filter design. In Figure 3, the
desired signal to be detected is the green trace with a peak
around 240 dB, the signal was captured with the interfering noise source off. As can be seen, when the noise source is
on – the blue trace – it covers the desired signal by 10 dB.
However, when the off the shelf filter was installed, the noise
source – the red trace – was magnified by another 10 dB.
This phenomenon was due to the difference in source impedance. When the suspect filter was tested in the lab using
Mil-Std-220B, the filter behaved as expected. Using IEEE
1560 Method contained in clause 10.4–“Variable Source Impedance with Current Injection”–, an 8 dB gain was observed
with less than 50 ohm source impedance.
79
Conclusion
Traditional methods for predicting the insertion loss of a power-line filter are simply not accurate at all times. Often, filters
are selected based upon specifications resulting from matchedimpedance, no-load testing and the impedance characteristics
of different power sources and loads are overlooked.
IEEE 1560 provides a set of test methods to achieve more
realistic attenuation data by using techniques of RF current injection, which can determine filter load performance and waveform quality without complicated test setups. The test methods
defined in IEEE 1560 will not only give a better indication of
the expected performance of power-line filters, but they will
also avoid many problems associated with testing under nonlinear load and mismatched-impedance conditions, which affect
the performance of power line filters.
Bibliography
[1] A. Tucker, 100/0.1 Ohm Filter Terminations and Other Extreme-Valued Affects,
1989 International Symposium on EMC, 8–10 Sept., 1989, Nagoya, Japan,
pp. 828–833, Vol. 2.
[2] H. Weidmann and W. J. McMartin, Two Worst-Case Insertion Loss Test Methods for Passive Power-Line Interference Filters, IEEE January 11, 1968.
[3] Heinze M. Schlicke, Assuredly Effective Filters, IEEE Transactions on Electromagnetic Compatibility, Vol. EMC-18, No. 3 June 1976.
[4] J.R. Fischer et at., Evaluating filters in situ under heavy load currents and normal working impedances, presented at the IEEE Electromagnetic Compatibility Symposium, Washington, D.C., July 1967.
[5] Robert E. Hassett, EMI Filter Characteristics and Measurement Techniques,
Interference Technology Engineers’ Master (ITEM) 1997.
[6] S. Eisbruck and F. Giordano, A Survey of Power-Line Filter Measurement Techniques, IEEE Transactions on Electromagnetic Compatibility, Vol. EMC-10,
No. 2 June 1968.
Kermit O. Phipps is a Senior PQ and EMC
Specialist at EPRI Solutions Incorporated, a
power quality engineering services and consulting firm, located in Knoxville, Tennessee. He
has over twenty-five years of experience in electronics, ranging from discrete component-level
troubleshooting to analog/digital system design.
As a Manual Electronic Warfare Test and
Component Specialist in the U. S. Air Force, he was awarded the Air
Force Accommodation Medal for his expertise and work with the
validation of the Automated Test System for the F/FB-111 aircraft.
In his seventeen year tenure at EPRI, he has conducted laboratory
investigations of electronic ballasts, transient voltage surge suppressors,
and uninterruptible power supplies, power distribution systems, and
other end-use equipment. His research and testing also focuses on electromagnetic compatibility (EMC), power-line filters, development of
EMC test instrumentation, and characterizing various types of radiated and conducted electromagnetic environments. Mr. Phipps is the
author of test plans, protocols, and research papers presented at international power quality conferences. He is also a member of the IEEE,
IEEE EMC Standards Development Committee, Chair of IEEE
EMC TC-4 Working Group, and served as the chairman of the
working group that developed IEEE 1560 Standard for Methods of
Measurement of Radio Frequency Power Line Interference Filter in the
Range of 100 Hz to 10 GHz. Mr. Phipps is a Certified EMC Engineer by NARTE (National Association of Radio and Telecommunications Engineers).
Philip Keebler is a Senior Power Quality
Engineer in the Power Delivery & Utilization
Sector at EPRI. His responsibilities include, 1)
conducting System Compatibility Research on
personal computers, lighting, medical equipment,
and Internet data center equipment within
EPRI’s System Compatibility Research Project
(SCRP), 2) managing EPRI’s Lighting Laboratory where the energy, electrical and photometric performance of light
sources, ballasts, and drivers are measured and the forensic analysis of
failed electronic lighting devices are carried out, 3) managing the
Electromagnetic Compatibility (EMC) Group where end-use devices
are tested for EMC, EMC audits are conducted, and solutions to electromagnetic interference (EMI) problems are identified, as well as, 4)
engaging in the research project identification and technology transfer
process for the EPRI Lighting Research Office (LRO). Prior to joining
EPRI in 1995, Philip worked with the North American Philips
Company in the Consumer Electronics Division where he designed
switch-mode power supplies, developed the first surge protection and
characterization laboratory there, and studied failure mechanisms and
rates associated with projection and direct view color televisions.
Don Heirman is a member of the IEEE EMC Society Board of
Directors and the EMC Society Standards Development Committee.
For a more complete biography visit www.donheirman.com
EMC
TC-3 Electromagnetic Environment:
From Sun Spots to 10 kHz
Dave Southworth, Chair, Electromagnetic Environment
Technical Committee, TC-3
At the 2009 IEEE EMC Symposium in Austin, Texas, the
Technical Committee on Electromagnetic Environment
(TC-3) meeting had a lively group of sixteen folks participate
as we reviewed our 2009 technical session, plans for the 2010
technical session and a 2010 special tutorial on the background of electromagnetic environment definition and standardization. Electromagnetic Environment standardization is
80
key to good product development and operation in this RFcluttered world we live in. The members, who were a slightly different mix then those who participated in the last year’s
symposium meeting in Detroit, listened to the announcement that the update review of the IEEE 473 “Recommended
Practice for an Electromagnetic Site Survey (10 kHz to
10 GHz)” would be started in November 2009. Several