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Electromagnetic compatibility

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Electromagnetic compatibility

Those Electromagnetic compatibility (EMV) it marks the usually desired condition that technical devices do not affect each other mutually by means of inadvertent electrical or electromagnetic effects disturbing. It treats technical and legal questions of the inadvertent mutual influence in that Electro-technology.

Table of contents

Basis

The use of electricity is always with the transformation of electromagnetic field energy into other forms of energy, e.g. in radiation energy (lamp), mechanical energy (engine) or warmth, connected. The fields remain not compelling within the electrical operational funds, but can spread also outside of the operational funds. Fields, which spread freely, can penetrate into electrical operational funds and affect the function of the operational funds. Operational funds, which serve radio communication, like e.g. Mobile telephones or wireless sets, are characterised by intended sending (mobile telephone) or intended penetration letting (wireless sets, mobile telephone) of fields.

The electromagnetic compatibility through e.g. covers all inadvertent or intended malfunctions of electrical or electronic operational funds. electrical, magnetic or electromagnetic fields and procedures. In it influences are already enclosed by rivers or tensions.

To the Sicherstellung of the electromagnetically compatible function of the electrical operational funds their adequate structure and organization are substantial. Proof and confirmation of insensitivity to interference and sufficiently small breakdown sending are regulated by EMV guidelines and EMV standards.

Those European EMV guideline defines electromagnetic compatibility as follows:

the ability of an apparatus, a plant or a system to work in the electromagnetic environment satisfyingly without causing at it even electromagnetic disturbances, for all apparatuses, plants or systems existing in this environment would be unacceptable.

From this the fundamental are derived protection requirements, which each electrical operational funds, which are in circulation brought, must keep. The protection requirements specify that on the one hand the breakdown sending of the operational funds must be so small that z. B. Broadcast receiver or other operational funds in the breakdown environment not to be inadmissibly affected. It concerns a delimitation of the interference sources. On the other hand variable disturbances the affecting which can be expected the operational funds (fields, interference currents or interference voltages) are not to impair its function. The operational funds must be developed thus sufficiently interference-resistantly.

For operational funds, which keep the relevant EMV standards, it may be assumed that the protection requirements are kept. That VDE and/or. those DKE is responsible in Germany for the production and treatment of the standards. Lately the standards are adapted increasingly on international level. Therefore international standardization organizations play how also for Germany International Electronical Commission, CENELEC and CISPR a ever stronger role.

Theory

The usual breakdown coupling model proceeds from the terms interference source, coupling path and interference sink. That Disturbances producing operational funds becomes as Interference source (English. SOURCE or culprit), the affected operational funds become as Interference sink (English. victim) designates. So that it lowers to an influence by the source come can, the disturbance must to lowers arrives, over there as Variable disturbance work to be able. And calls one lowers the way between source Coupling or Coupling path. Criterion of the quality of a signal transmission is in the EMV that Signal-to-noise ratio.

One differentiates between natural and technical interference sources and interference sinks. As example to a natural interference source is considered Lightning, natural lowering organisms can be. Typical technical interference sources e.g. are. Frequency static frequency changer, typical technical interference sinks e.g. are. Radio reception devices.

During the influence of organisms by electrical, magnetic or electromagnetic sizes one speaks also of electromagnetic environmental compatibility or EMVU. The protection in relation to lightnings becomes under the term Lightning protection treated. The protection in relation to electrostatic unloadings is frequently likewise separately regarded.

The following coupling mechanisms are differentiated:

  • Those Galvanic coupling, technically more exactly Impedanzkopplung, develops at common impedances of the interference current circle with the electric circuit of the interference sink. This common elements or line sections of both electric circuits can be, over e.g. Balancing currents flow, those over the impedance of the common line section tensions launching. With printed circuit boards a Impedanzkopplung develops if necessary. also over not sufficiently dimensioned mass courses and backup capacitors. Note: At the latest here is the term Impedanzkopplung technically the usual term galvanic coupling to prefer, since a condenser does not offer a galvanic connection.
  • Capacitive coupling designates the influence by electrical field, e.g. Over coupling on parallel led ladder in a cable or a troughing or parallel led conductive strips on a printed circuit board. This effect knows z. B. arise between parallel-led lines with high impedance terminating impedances.
  • Inductive coupling designates the influence of an interference sink by Magnetic field. The inductive interconnection results from magnetic field linking, usually in conducting circuits, z. B. between parallel-led conducting circuits, which exhibit low impedance in each case terminating impedances.
  • Of Mutual coupling one speaks, if an electromagnetic field affects an interference sink. Electrical conductor of a cable or on plates know as Antenna e.g. work and. Radio or radio signals receives on the leader as spurious signals develops.

Kinds of disturbances

In the EMV becomes between line-bound and field-bound Disturbances differentiated.

  • Those line-bound disturbances by the interference source directly over supplying or signal lines to the interference sink are transferred.
Cracking in the radio can be caused for example by switching a refrigerator off, switching supply voltage assistance off of a thermal relay produces tension pulses with a spectrum in the audible frequency range. If these tension pulses are led across the supply line to the radio and demodulated there, it comes to a crack disturbance. Remedy creates frequently filtering.
  • Those field-bound disturbances for example as electromagnetic field to the interference sink are transferred and received there for example from a leader functioning as antenna. Also capacitive and inductive influences electrically and/or. magnetic fields field-bound disturbances are called.
An example of a field-bound disturbance is linking one GSM-Mobile telephone- Transmission to an audio mechanism, z. B. into a car radio or into a fixed net telephone. Reason for it cannot sufficiently more protected Loudspeaker its.

The typical interferences are caused for example by GSM Mobiltelefone, there these the HF-carrier low-frequency, in the audible frequency range, after one Time division switch on and off. In loudspeakers it can through Induction to a tension and into consequence its to interferences come.

Emergence of the disturbances

A disturbance is produced by the fact that in the interference source a tension or a river becomes varied (modulates or switched). From this results then transient or periodic tension and/or in the time intervall. Current changes U (t) and/or. I (t).

Physically conditionally these signals U (t) result in and/or. I (t) of the time intervall electromagnetic spectrum in the frequency range U (ω) and/or. I (ω). These work themselves then if necessary. as measurable disturbances in an unwanted frequency range out and over the ouple mechanisms described above are spread. Mathematically this behavior is described with the help of that Fourier transformation, which transforms a Zeitfunktion f (t) into a spectral function F (ω) (with: ω = 2πf).

With one Square wave pulse e.g. contain the respective flank changes the entire spectral achievement. Associated disturbances can be for example reduced, by the flank change for each time interval (slope) ΔU/Δt and/or. ΔI/Δt is slowed down.

The EMV interference sources can be artificial or natural origin. Examples are:

Delimitation of the disturbances

Through Noise suppression at the interference source and sufficient Noise immunity a delimitation of the disturbance is possible for the interference sink.

Locally

With that EMV fair circuit interpretation (local, Intrasystem EMV) one aims at

  • to avoid unnecessary shifting processes
  • to implement not avoidable shifting processes as slowly as technically justifiablely
  • to limit the not avoidable disturbances by appropriate Design locally as closely as possible, thus e.g. to screen mechanical switching contacts by parallel switched RC elements to shield housings and lines to throttle cable outlets.
  • With electronics a EMV fair plate layout (e.g. To adapt conductive strip lengths to the frequencies, pig pus plates etc.)
  • to ensure a sufficient noise immunity, e.g. by filter, Abblockkondensatoren, errortolerant software with multiple inquiries and plausibility checks.

Global

With trade-spreading the EMV protection (global, Intersystem EMV) it arrives to it

  • to determine by systems analysis interference sources and interference sinks
  • by suitable measures e.g. reach the protection goal. Noise suppression the interference source
  • Distance
  • Shielding
  • Increase that Noise immunity the interference sink
  • etc.

By the introduction of a interference protection zone concept with defined site conditions for those devices which can be operated in each case can the EMV in plants and systems be ensured.

Transmitting plants

A television station or a mobile telephone is to send straight with maximum efficiency, produce thus radiation.

So that this radiation does not disturb other devices, the passive EMV Design is just as important. That means:

  • Installation of Harmonic waves-Filter (Screening units)
  • Inlets shield
  • Cable entries screen (System filter, Signal line filters)
  • Housings shield
  • Printed circuit boards in such a way lay out that no unintentional antennas develop
  • Change of the arrangement of the electronics construction units concerned and/or. the structure and/or the layout of the printed circuit boards, which carry these components. This is often the best measure, since she reduces „the root “of the evil, thus the electromagnetic couplings, and not as with a shielding/a filtering only the symptoms lindern is. For this purpose, thus to the optimization of the board design, there are numerous software solutions.
  • Intelligent interpretation of the radio communication systems in frequency, achievement, radiation direction and type of modulation, so that they do not radiate any more than necessarily and other radio communication systems and devices disturb.

Technical consequences

The electromagnetic waves can for example in circuits Tensions and/or. Rivers produce. These can in the simplest case to a noise in Televisionlead, in the worst case to the loss of electronics. The electromagnetic compatibility guarantees that for example Cardiac pacemaker, control electronics of motor vehicles or Airplanes) does not precipitate. Thus e.g. forbid. Hospitals Mobile telephones within certain ranges; also in Airplanes is the enterprise of Mobile telephones under menace of high punishments forbids. Even in motor vehicles (starting from year of construction 1995) the start-up of a mobile telephone is permitted only if one is present after the manufacturer guidelines installed outdoor aerial, otherwise can the general operating permit (ABE) expire.

Effects on the environment

Electromagnetic waves have also influence up Humans and those natural Environment; therefore must also on those Electromagnetic environmental compatibility (EMVU) to be respected.

Legal regulations

Those Power supply firm and that Legislator prescribe for the manufacturers of electrical appliances in the European Union, in Germany by that Law over the electromagnetic compatibilityto keep, appropriate protection requirements, those by limit values to Noise immunity or to Breakdown sending in relevant Standards are laid down. More to this topic is under the keyword CE-marking[1] with information on the EMV guideline, which must often be used together with the low-voltage guideline.

As a rule the adherence to the protection requirements is assumed, if the harmonized European standards applicable to the equipment are kept around all customer and citizen a troublefree enterprise from electrical appliances to to ensure. This leads often to the fact that that, which offers a coming on the European market, EMV examinations or equivalent proof procedures anzuwendet, in order to prove the EMV. As equivalent proof procedures are suitable, depending upon equipment, with technically simple already simple Plausibilitäsbetrachtungen. Thus one becomes for example Lamp, which does not contain electrical or electronic construction units except the filament, for itself taken in the enterprise no limit values for high frequency emissions exceed.

During the last years within of Europe attempts were undertaken to adapt the limit values and basic conditions of different countries together e.g. in the context of the EMV guideline. In Germany those worry Federal net agency (formerly Adjustment authority for telecommunications and post office), that Federal Office for radiation protection and those German Federal Armed Forces within the framework that BEMFV (Regulation on the proof procedure for the delimitation of electromagnetic fields) around the adherence to of the protection requirements or the limit values.

Measuring instrument manufacturer (alphabetical)

Footnotes

  1. ↑ CE-Zeichen.de

Literature

  • Joachim Franz: EMV, interference-proof structure of electronic circuits. Teubner, Stuttgart Leipzig Wiesbaden 2002, ISBN 3-519-00397-X.
  • Hate, E. And. Landers, J. Wiesinger, P. Number man: VDE series of publications volume 185. EMV - Lightning protection of electrical and electronic systems in structural plants - risk management, tarpaulins and implementing according to the new standards of the row VDE 0185-305. 2. complete. over work. and erw. edition. VDE publishing house GmbH, Berlin 2007, ISBN 978-3-8007-3001-8.
  • Adolf J. Schwab, Wolfgang Kürner: Electromagnetic compatibility. Springer, Berlin 2007, ISBN 978-3-540-42004-0.
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