2.sources emi principles

7/29/2019 2.Sources Emi Principles

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EMI Sources & EMC

Technologies

[email protected]


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- un amenta s o

Coupling of EMI

Electrostatic discharge

EMI in circuits and systems

Transients in power supply lines Nonlinearities in circuits

ass ve n er-mo u a on

Crosstalk in transmission lines

Illustrative examples


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stur ance Any electromagnetic phenomenon that may degrade

the performance of a devise, equipment, or system, or adversely affect

living or inert matter (an electromagnetic disturbance may bee ec romagne c no se, an un-wan e s gna , or a c ange n e propaga on

medium itself)

EM interference Degradation of the performance of a device, equipment,or system caused by an electromagnetic disturbance

EM compatibility The ability of a device, equipment, or system to function

satisfactorily in its electromagnetic environment without introducing


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Sources of EMI


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EM Fields


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EM Fields (contd.)


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Acetate

Asbestos

ar ru er

Mylar

Epoxy glass

Human hair

Nylon

Wool

, ,

Brass, Stainless steel

Synthetic rubber

Acrylic

Fur

Lead

Silk

Polystyrene foam

Polyurethane foam

Polyester

um num

Paper

Polyurethane

Cotton

aran

Polyethylene

Polypropylene

PVC Vin l

Wool

Steel

Sealing wax

Teflon

Silicon Rubber


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rans en over-vo ages pro a y as a resu o erres r a p enomena suc

as lightning

Radiation from strong radar/radio/communication transmissions within the

vicinity, which are picked up by the power transmission lines

Sudden decrease or increase in the mains voltage (caused by the switchingof low impedance loads)

Burst of high frequency noise (probably due to switching of reactive loads)


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A nearby lightning strike to objects

-

The rapid drop of voltage

A direct lightning strike to high-voltagerimar circuits

Lightning strikes the secondary circuits

e y


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Sur e volta es from li htnin


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Transients due to Li htnin


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Minor switching near the point of interest

Periodic transients (voltage notching) that occureach cycle during the commutation in electronic

power converters

Multiple re-ignitions or re-strikes during a switcho eration

Major power system switching disturbances

,

arcing faults


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Passive Intermodulation (Materials and

Practices for reducing PIM)

ver p ate type connectors avo ow-pressure contacts

Terminations or attenuators made with alloys or oxides of non-

ferrous metals

Good, clean dielectric material

Smooth well-executed weld

Soft solder (satisfactory if well executed)

Clean and dry surfaces

must be rounded


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Passive Intermodulation Materials and

practices to be avoided erromagne c ma er a s even no n e cav y

Non-magnetic stainless steel

Ferromagnetic bolts Circulators, isolators made with ferrites

Terminations or attenuators made by plating nicrome or other ferromagnetic materials

Terminations or attenuators with composite resistive material

Hermetic seals (generally made with ferromagnetic materials)

Strip-line components (unsatisfactory, probably due to sharp edges or conductive

strip)

at ng over erromagnet c sur aces (even a thick fiber cannot guarantee

suppression of PIM)

Dielectrics loaded with conductive powder granules (contacts between granules

Multi-layer thermal wrap made of aluminum-coated Mylar (not to be used in high

strength RF field areas)


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SI anal sis - model


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C t lk


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Cross talk


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(contd)


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(contd)


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