Electromagnetic Compatibility Comes of Age

The science of electromagnetic compatibility has been in exis­tence for several decades. As an art, it goes back much further, perhaps to the time of Edison when he was just beginning to experiment with practical electrical devices. I am sure that with some of his more sophisticated devices undesired interac­tions took place because of inadequate shielding or filtering. Certainly, with the advent of radio, incompatibility problems occurred as a result of the poor quality of transmitters and receivers. Perhaps the first formal recognition of electromag­netic compatibility problems occurred when the telephone and power companies found they had mutual coupling problems when their lines were carried on the same utility poles. Later on, the increasing use of the radio spectrum called for formal controls administered by departments in the post, telephone, and telegraph offices in many countries, or through the Feder­al Communications Commission in the United States.

Until recently, problems in electromagnetic compatibility were solved by specialists having familiarity with the equip­ments and systems which exhibited interactions and who received relatively little recognition for their accomplishments, except when their efforts failed, in which case the recognition was not particularly complimentary. Furthermore, these experts worked under extremely trying conditions, especially when called upon to solve problems that had arisen because of poor design of equipment, improper application and use of equip­ments, or because of sudden changes in environmental condi­tions which they were powerless to do anything about. In par­ticular, they were usually called upon to solve problems “after the fact,” when, if they had been called in on initial design and systems engineering stages, the problems encountered could have been entirely avoided. Except for the technical areas that have been mentioned and in the area of military electronics, where achieving electromagnetic compatibility was essential because of the high concentration of equipment and its fre­quently highly sophisticated nature, the EMC engineer obtained few rewards for his efforts. His accomplishments were attained through sheer dedication.

We are now on the threshold of a new era. Evidence of this fact includes the following: (a) the recent establishment of a new technical committee in the International Electrotechnical Com­mission on electromagnetic compatibility, TC 77, (b) interest demonstrated in the past several years by many manufacturers in determining what electromagnetic compatibility characteris­tics their equipment should have both from the point of view of their emission characteristics as well as their susceptibility char­acteristics, (c) increasing emphasis on the application of electro­magnetic compatibility requirements in international trade, (d) the re-establishment of a group concerned with radio noise in Commission 8 of URSI, and finally (e) the recognition that elec­tromagnetic characteristics of the environment must be described and controlled along with many of the other tradi­tional characteristics such as temperature, pressure, humidity, chemical contamination, etc.

If the concept of a new era is accepted, then one might well take a few moments to reflect upon the status of the field of technology and perhaps speculate on what the future holds. In the first place, with new recognition, one should recognize new responsibility. The EMC engineer will be required to define this area of competence clearly in relation to other areas of special­ization, and to show all the potential users how his work can contribute to the solution of their problems. His services must be packaged in such a way that their value will be recognized. This may not be easy since the EMC area has so many dimen­sions. All types of electronic and electrical equipment are involved, and the techniques can be applied in early design stages, in development stages, in production stages, and in installation stages. Furthermore, the technology changes rela­tively rapidly. For example, the increased use of digital trans­mission techniques as compared to analog techniques requires new technology. Frequency ranges have changed, bandwidths have changed, and cor­respondingly methods of avoiding interfer­ence problems have changed. While much change has taken place over the last 15 years or so, we can expect more extensive application of digital tech­niques in the coming years.

It is because of examples such as this that this conference and other conferences like it are important. They are evidence of the dynamic nature of the discipline and provide opportunities for practitioners of the field to exchange notes on new problems, new methods of analysis, and new methods of solution. They also provide opportunities for persons with limited experience in the field to quickly become aware of the state of the art.

At this point, one may well ask—what is the future of the field? It lies in several areas which can be grouped into four cat­egories: first, developments in adequate quantitative theories applicable to fundamental electromagnetic phenomena; second, development of new and improved techniques in electromagnetic compatibility control including methods of measurement of emission and susceptibility levels; third, development of components; and fourth, development of standards.

The theoretical problems include more accurate solutions of shielding properties of various configurations. Exact solutions for the shielding effects of coaxial structures are still not readily available to the practitioner. In the same general area, currently there is much effort on shielding from transient fields. Another area which still needs work is the theory of grounding. Here, the general principles are well understood but quantitative information on the optimum ground arrangements under par­ticularly operating conditions is still not generally available.

Techniques of measurement and control of interference are needed in many areas. While the regulatory authorities have devoted much attention to the protection of radio broadcasting, control of electromagnetic compatibility in industrial opera­tions is only beginning to get the attention that it deserves in the public market place. Undoubtedly, individual engineers working in particular companies have treated many of the prob­lems which are likely to arise, but there does not appear to be available as general a body of knowledge as is needed. In addi­tion, further work is needed in the development of techniques of measurement of both emission and susceptibility characteris­tics of all classes of equipment, especially with regard to their broadband and pulse characteristics.

In the component area, new types of wiring and cabling, including strip lines and means of protecting such lines, new methods of interference suppression, especially of the impulsive type, integrated circuits, and the development of optical wave­guides can have major impacts on the field.

Finally, particular emphasis should be placed on the area of standardization. It is not appropriate to review the importance of establishing standards. Clearly, they have an important func­tion in encouraging trade through the economies which are affected in man­ufacturing and in engineering. In line with the theme of this particular pre­sentation, I should like to refer to the often quoted state­ment that, in fact, standards are an expression of the state of the art. Before one can write a stan­dard, there must be a technology available which has general application. It must be based upon aspects of the science and the art which are widely understood and accepted. Until that state has been reached, standards cannot generally be written which are significant. Extensive work in standards is done at various levels within individual companies, within particular indus­tries, and at national levels. At this conference, it is well to emphasize the international aspect. In the electromagnetic com­patibility field, CISPR has been active for about 40 years. Its effectiveness in producing standards of general applicability is probably one of the more outstanding achievements of this kind of effort. The documents are highly respected and reflect work performed at a high technical level. In the past 10 years or so, the importance of the electromagnetic compatibility discipline has received broad recognition in the electro-technical field. A number of IEC technical committees have shown an interest in preparing standards related to their particular scopes. Because of the cross-disciplinary nature of the problems involved, the IEC has recognized the importance of centering this activity in a separate technical committee, and the formation of TC 77 was approved last year. This committee had its first meeting in Bucharest in September 1974.

At the present time, there is no apparent conflict in scopes between the CISPR and TC 77. TC 77 has undertaken to deal with low frequency phenomena; in particular harmonics of the power line frequency up to perhaps as high as 2500 Hz, and flicker phenomena which occur at a few cycles per second. While the phenomena involved are not new, the fact is that the problems caused by these effects are assuming increasing impor­tance, especially in view of the development of solid-state tech­niques for power control. These devices, unless very carefully designed, are likely to introduce substantial harmonic and puls­ing currents into the power supply system. These can react not only on sensitive equipment connected to the same power line, but can also create substantial problems in the power distribu­tion equipment and control techniques associated with that equipment. Solutions to these problems are necessary and can be expected to have substantial economic impact. It is therefore necessary that all of the available expertise be assembled to dis­cuss them.

While TC 77 is concerned with some rather special problems at the moment, at the meeting in Bucharest the delegates were surveyed with regard to their general interest in other problems. The response was substantial. Included were problems in tele­control, industrial equipment, electronic data processing con­trol, radio communications, machine tools, medical equipment, and other areas. The spectrum of interest extended well into the megahertz range and clearly overlaps the areas of concern of CISPR in many respects. Just how this work will be developed in the future is the subject of study of a special Committee of Action working group.

It is perhaps of interest to speculate on standards develop­ments in the immediate future. First, the need for industrial standards will be met in large measure by reference to the basic techniques used in controlling radio interference. For example, the fundamental basis for setting limits for protection of broad­casting has been levels of field strength to be protected. For the development of electromagnetic compatibility standards, clearly the criteria can be different. In industrial areas the objective is not the protection of broadcasting field strengths, but the obtaining of mutually compatible levels of emission and suscep­tibility. Although these may vary from industry to industry and from one location to another location in any given industry, there is surely a need for standards that can be invoked generally.

These standards cannot be set independently of those applied in broadcasting, since industrial equipment is already limited for this purpose. But, because of its location, it is permitted higher emission levels than in the home. In line with this, sen­sitive equipment used must have good susceptibility (immuni­ty) characteristics, but a rational basis for establishing appropri­ate limits does not yet exist.

The program for this symposium contains a large number of papers which directly relate to this question of setting standards for achieving electromagnetic compatibility in various specific environments including urban, industrial and commercial areas, hospitals, aircraft and other, including pertinent measurement techniques. It is clear that rapid advances can be expected in the near future.

Practitioners in the field can look to opportunities to con­tribute to these efforts in the future, and they will be stimulat­ed quite substantially by the outputs of these efforts.

This speech was the Keynote Address given by Dr. Ralph Showers at the 1st Symposium and Technical Exhibition on Elec­tromagnetic Compatibility held in Montreux, Switzerland, from May 20-22, 1975. At the time, Dr. Showers was with the Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia, PA. Dr. Showers was active as the Chair of CISPR as well as the Chair of the American National Standards Institute (ANSI) Accredited Stan­dards Committee C63® (electromagnetic compatibility).

Reprinted with permission of the IEEE EMC Newsletter, Winter 2009, Issue 220

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