ELEKTRO MANYETİK UYUMLULUK SLAYT
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Transcript of ELEKTRO MANYETİK UYUMLULUK SLAYT
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EMCThe operation of all items of electrical and
electronic equipment can disturb the operationof other nearby items of electronicequipment.
That disturbance is calledas Electro Magnetic Interference(EMI)
The immunity to effects of EMI is namedElectro Magnetic Compatibility(EMC).
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How Does EMI Affect Electronics? Radiated and conducted interference
Conducted Interference Enters and Exits Equipment throughWiring and Cabling
Radiated Interference Enters and Exits Equipment throughWiring and Enclosure Penetration
Radiated Susceptibility Radiated Emissions
Conducted Susceptibility Conducted Emissions
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Surge Coupling
Lightning and pulse sources cause high-energy transients into power and datacables
IndirectDirect
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Interference couplingmechanisms
coupling path
Directcoupling
Radiatedcoupling
source
victim
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coupling path1. Direct coupling
Coupling viapower or
signal lines
Commonimpedance
coupling
6
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1. Direct coupling
Coupling viapower or
signal lines
7
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Commonimpedance
coupling
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Interference to TV Reception
Two Interfering Signals Injected into TV
No Interference
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The modified DC power supply with significantly improved EMC performance
Circuit diagram of a simple regulated DC power supply
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C5, C6, C7 and C8 provide additional decoupling (effective at high-frequencies)inorder to prevent instability in IC1 and IC2.Without these components, theregulatorcircuits may oscillate at a high-frequency
C9 and C10 provide additional high-frequency decoupling to remove noise present
on theoutput voltage rails.C11, L1, L2, C12 and C13 provide a low-pass supply filter to remove noise and
spurious signals resulting from the harmonics of the switching action of the dioderectifiers. This filter also reduces supply borne noise that would otherwise enter theequipment from the supply
A low-resistance ground connection is introduced to ensure that there is an effectiveconnection between aircraft ground and the equipment chassis
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Effect and causes of EMIThe effects of EMI include
errors in instrument indicationsheterodyne whistles present on audio
signals,
herringbone patterns in video displays,
repetitive pulse noise (buzz) on phonesystems,
desensitising of radio and radar receivers,
false indications in radar and distancemeasuring equipment,
unwarranted triggering of alarms, and so on.
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Sources of EMIFluorescent lights,
Radio and radar transmitters,Power lines,
Window heat controllers,
Induction motors,
Switching and light dimming circuits,
Microprocessors and associated circuitry,
Pulsed high frequency circuits,
Bus cables,
Static discharge and lightning
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Types of interferenceNarrow band interference
is caused by devices generating specificfrequencies
AC power rails, microprocessor clocksradio transmitters and receivers...
Broad band interferenceis caused bydevices generating random frequencies andnoise
Examples ,power supplies ,LCD, switchedmode power supplies, switching powercontrollers, and microprocessor bus
systems
EMI d ti
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EMI reduction
1. Suppress interference at source
Enclose interference source in a screened metalenclosure and then ensure that the enclosure isadequately grounded
Use transient suppression on relays, switches
and contactors
Twist and/or shield bus wires and data bus
connections
Use screened (i.e. coaxial) cables for audio
and radio frequency signals
Check that enclosures, racks are grounded
effectively.
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2. Reduce noise coupling
Separate power leads. Twist and/or shield noisy wires and data bus
connections
Fit an optical fibre data bus where possible Use screened (i.e. coaxial) cables for
audio and radio frequency signals
Keep ground leads as short as possible. Filter noisy output leads.
Physically relocate receivers and sensitive
equipment away from interference source.
3 I i ibili h h ld
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3. Increasing susceptibility thresholds
Limit bandwidth to only that which is strictly
necessary
Limit gain and sensitivity to only that which is
strictly necessary
Ensure that enclosures are grounded and that
internal screens are fitted
Fit components that are inherently less
susceptible to the effect of stray radiatedfields.
Ai ft i i d bli
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Aircraft wiring and cabling
1.Adequate wire separation should be maintainedbetween noise source wiring and susceptible wiring
2.Wire lengths should be kept as short as possibleto maintain coupling at a minimum.
3.Equipment grounds must not be lengthened
beyond design specification.
4. With the aid of the technical manuals, groundingand bondin inte rit must be maintained.
G di
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Grounding
Connecting objects to either a structureor other return path to make circuitcomleted.
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.1 Protect aircraft, crew and passengers against
the effects of lightning discharge 2. Provide return paths for current
3. Prevent the development of RF voltages and
currents
4. Protect personnel from shock hazards 5. Maintain an effective radio transmission and
reception capability
6. Prevent accumulation of static charge.
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BondingElectrical connecting of objects that are not
otherwise adequately connected.1.Equipment bonding: Provide radio frequency
return circuits and to facilitate reduction in
EMI.2.Metallic surface bonding: Connected to the
airframe . Capable of conducting static charges
and lightning strikes.
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3. Static bonds :Connection to the aircraftstructure to dissipate possible static charge
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CONDUCTED EMISSIONSTESTING
Measure Noise on Power Line
Spectrum Analyzer
Product
PowerCord
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RADIATED EMISSIONS TESTING
Test Site: Measure Radiated Noise from Equipment Case
and Cables
Measuring Antenna
Product
3 m or 10 m
SpectrumAnalyzer
Open Area Test Site
Turntable