Practical EMC and EMI Control for Engineers and Technicians

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Technology Training that Workswww.idc-online.com/slideshare

Practical EMC and EMI Control for Engineers

and Technicians

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Oops ...

Falklands war: HMS Sheffield turned off the missile warning radar - interfered with the satellite communication system. Sunk by a missile

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… oops!

Feb ’99: DC 10 approaching JFK. Banked left, almost caused a crash. CD player in 1st-class suspected.

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Structural Engineering“ … the art of modelling materials we do not

understand, into shapes we cannot precisely analyse, to withstand forces we cannot properly assess, in such a way that the public at large has

no reason to suspect the extent of our ignorance”.

(past Chairman of the Scottish branch of the Institute of Structural Engineers)

Sound Familiar?

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Vocabulary: EMC vs EMI

EMI - Electromagnetic Interference

» This is the PROBLEM

EMC - Electromagnetic Compatibility

» This is the SOLUTION

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Intermittent EMI Sources

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The Need for Standards Standards are needed to control/limit interference

from electronic devices Standards are also needed to make electronic

devices less susceptible to interference Various countries implemented their own

standards Any manufacturer wanting to market goods into

that country, has to comply with the standards

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EMC - the issues

Controlledoutptuts

Control/signalinputs

Disturbing or emitted

surges

Radiated or conducted RF,

emitted harmonics

Radiated EMD

Susceptibilityto EMD

Radiationfrom

outputs

Susceptibilityto EMD

Earth coupling/ bonding

problems

PQ phenomena

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Electromagnetic disturbances(any electromagnetic phenomenon which may degrade performance, without regard

to frequency or coupling method)

Supply voltage» interruptions» dips» surges» waveform distortion» fluctuations

slow rms variations rapid rms variations (flicker)

» Voltage unbalance» Frequency variations» DC in AC networks» Power-line carrier signaling

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Electromagnetic Disturbances Transient overvoltages

» supply lines» signal lines» control lines

lightningswitchingESD (electrostatic discharge)

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Electromagnetic Disturbances

Radio frequency fields» pulsed (radar)» modulated» continuous» coupled directly to equipment» coupled into connected cables

LF magnetic or electric fields NEMP (Nuclear Electromagnetic Pulse)

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Radiated Emissions (RE)

POWERSIGNALS

Conducted Emissions (CE)

POWER

SIGNALS

NOISE

CURRENT

Radiated

Conducted

Emissions

Susceptibility / Immunity

Radiated Susceptibility (RS)

POWERSIGNALS

DISTURBANCE

SIGNAL INJECTED

Conducted Susceptibility (CS)

POWER

SIGNALS

EMC Testing Categories

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Electromagnetic susceptibility The inability of a device, equipment or system to

perform without degradation in the presence of an electromagnetic disturbance

ORImmunity

(to electromagnetic disturbances) The ability of a device, equipment or system to

perform without degradation in the presence of an electromagnetic disturbance

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The compatibility gap

ValvesTransistors

ICs

SwitchgearRadio/Radar/

TV

CellphonesIndustrial

electronics

Decreasing immunity

Increasing emission

EMC Directive

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Emission, immunity & compatibility

Immunity level

Immunity limit

Emission level

Emission limit

Compatibility level

Immunity margin

Emission margin

Compatibility margin

Design margin

Design margin

Independent variable

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Considerations Consequences of EMI

» catastrophicdeath; major injuries; downstream consequences

» criticalminor injuries; extensive damage

» majorminor permanent damage

» minortemporary performance loss

» inconsequentialloss of performance within tolerance;

no human intervention needed

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Test result classification Normal performance within specified limits temporary degradation or loss of function; self-

recoverable temporary degradation or loss of function; requires

human intervention or system reset degradation or loss of function due to physical

damage; software or data corruption

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Levels of Compliance

Self Compatibility

SpecialRequirements

• Harsh Environment• Exceeds Standards• Environment Dominates

• Functional• Just making it work• No EMC design rules

• Self Imposed• Improved Integration / Functionality• Basic EMC design rules• Minimum Specification / Standards

Contractual Compliance

• Electrical & EM Environment (E3)• To Specification• EMC Engineering• Mandatory Testing

Minimum Engineering / In-house standard

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Areas of EMC Engineering Application

PCB’s» Most subtle, but very cost effective

Circuits and Filters» Added circuitry to contain EMI» Adds cost but a necessity for good EMC design

Screening» Enclosures and cables» Brute force - least cost effective

Grounding» Applicable to all three areas above

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Practical EMC and EMI Control for Engineers and Technicians

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