资源描述：
《丹佛斯变频器FC51应用说明》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。
1、ContentsContentsIntroduction3NormalSituationwheretheThreePhasesareBalanced3OnePhaseMissing4VoltageononePhase3%Higher4VoltageononePhase3%Lower5VoltageononePhase3%Higherand3%LowerononeoftheOtherPhases5OneDiodeInterrupted6NormalSituationbutaveryStiffMain611HarmonicMeasurements121HarmonicMeasurements1.
2、1.1IntroductionThefollowingpagesdescribecurrentharmonicsunderdifferentconditions.1Theaimofthisapplicationnoteistoimproveusers'backgroundknowledgetoevaluateharmonicmeasurements.Allharmonicsshownarefora6-pulserectifier(threephasesupply).Theconditions,whicharecoveredinthisapplicationnote,are:1.Normals
3、ituationwherethethreephasesarebalanced.2.Onephasemissing3.Voltageononephase3%higher4.Voltageononephase3%lower5.Voltageononephase3%higherand3%lowerononeoftheotherphases6.Onediodeinterrupted7.Normalsituationbutaverystiffmain1.1.2NormalSituationwheretheThreePhasesareBalancedTheharmonicspectrumbelowsho
4、wsnaturalharmoniccurrentsgeneratedbyanon-linear3-phaseoverload(likeafrequencyconverter).Theharmoniccurrentsgeneratedbynon-linearloadaregivenbytheformula:h=p×n±1wherepisthepulsenumberofthenon-linearload(p=6fora3-phasefrequencyconverter),narepositiveintegerstartingfrom1→∞.Regardingharmonicmeasurement
5、sonlyharmonicsforn≥50areofinterest.Theaboveformulashowsthatthenaturalharmonicsare:5,7,11,13,17,19,23,25,29,31,35,37,41,43,47,49...∞Measurementsonarealapplicationwilloftenshowaminorcontentofotherharmonicsaswellduetothefactthatthemainsneveris100%balanced.Themagnitudeoftheindividualharmonicdependsonth
6、eloadandontheimpedanceofthesystem(cable,transformer,etc.)31HarmonicMeasurements1.1.3OnePhaseMissing1Thegraphshowstheharmonicspectrumifoneofthephasesismissing.Besidethenaturalharmoniccontent,thereisahighcontentof3rdharmonic(150Hz).Multipleofthe3rdharmonic(6.,9.,etc.)arealsopresent.1.1.4VoltageononeP
7、hase3%HigherIfthevoltageofoneofthephasesishigherthanthevoltageontheothertwophases,theharmoniccontentisthesameasifonephaseismissing,butthemagnitudeoftheharmonicsarenotequalatthethreephases.41HarmonicMeasurem
