EMI Power Filters Catalog - Spectrum Control - Master-tool

Application GuidelinesNeed for EMI suppressionGlobal regulatory agencies have established limits tothe amount of noise that man-made electronic devicescan radiate or conduct. These regulations have gainedgreater importance as the world’s electronic populationintensifies and the proximity of electronic devicesbecomes closer.EMI can propagate through two basicavenues: Conducted and RadiatedConducted refers to events where the EMI energy flowsthrough power lines, data cables and other wiring thatcarries functional data or power.Radiated refers to energy that is propagated bymagnetic or electric fields, which originate from otherelectronic or electrical systems.Interference typesThere are two modes of conducted noise: differentialmode (symmetrical or normal mode) and common mode(asymmetrical mode).Differential mode interference signals are present onone side of the line, referenced to the other. The currentsflow along one phase and return along another phase.Common mode interference signals are present on bothsides of the line referenced to ground. The current flowsfrom the source to ground along the ground path andreturns along the phases.Sources of EMIElectromagnetic interference can occur naturallyor through electronic sources. Lightning discharges,precipitation, sand and dust storms, and cosmic noiseare sources of natural EMI.EMI generated from power electrical products causethe most concern. These man-made sources, such aspower lines, rotating machinery, power supplies andelectronic transmission devices, all have their ownsignatures and noise pollution.EMI filters, insertion lossand attenuationPower line EMI filters are designed to attenuate(or reduce) all radio frequency emissions or energy thatis above the applicable EMC specification. Most powerline EMI filters utilize inductor/capacitor “low pass” componentconfigurations that pass all DC or low frequencyAC necessary energy and attenuate (suppress) higherfrequencies containing noise or unwanted energy.Power Filter InstallationPOWERINPUTLINEFILTERINCORRECTCABINETDENOTESCOUPLINGFROM NOISYCIRCUITSBACK TOLINEPOWERINPUTCLEANLINECORRECTLINE FILTERCABINETDENOTESCOUPLINGFROM NOISYCIRCUITSBACK TOLINETo insure a customer’s “in system” unit to unitattenuation uniformity of power line filters, an insertion lossproduction line test is performed by Spectrum Control, Inc.Each of the specific frequencies is measured usingRF test equipment and the “reference signal level” ofeach frequency is stored. Some systems sweep the entirefrequency range and store this “reference signal level”. Thefilter to be measured, tested, or evaluated is then “inserted”between the generator and receiver that established thestored “reference signal level” on the RF test analyzer.The measured difference without a filter (“the referencesignal level”) and with the filter “inserted” into the RF testequipment/analyzer is defined as insertion loss. The unitof measure for insertion loss is the decibel (dB). As notedon most curves in this bulletin, as frequency increases,the higher the insertion loss or dB value. The plot offrequency versus dB value establishes the typicalinsertion loss curve.Installation CriteriaProper installation of a filter network is critical to achievingsuccessful filtering of electromagnetic interference.Spectrum Control recommends that power line filters beinstalled where the power line enters the equipment. Thefilter acts as a barrier between polluted energy and cleanenergy going into your equipment. It is important that thefilter is connected to an effective ground plane and whereproximity does not couple radiated noise to the clean lines.8SPECTRUM CONTROL INC. • 8031 Avonia Rd. • Fairview, PA 16415 • Phone: 814-474-2207 • Fax: 814-474-2208 • Web site: www.spectrumcontrol.comSPECTRUM CONTROL GmbH • Hansastrasse 6 • 91126 Schwabach, Germany • Phone: (49)-9122-795-0 • Fax: (49)-9122-795-58