【文档说明】Y形起电力不平衡Y形负荷.pptx，共(10)页，72.554 KB，由精品优选上传

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7.3Y形起電力+不平衡Y形負荷7.3Y-ConnectedPowerSupplies+UnbalancedY-ConnectedLoadsこのテーマの要点•三相Y形方式の一般的な計算Generalcalculati

onofY-connectedthreephasesystem教科書の該当ページ7.2.1(b)Y起電力回路、不平衡Y結線負荷[p.156]Y形不平衡負荷回路[p.156]線路電流を求め、ベクトル図を描くCalculatelinecurren

tanddrawvectordiagram条件非対称三相起電力AsymmetricthreephasepowersupplyEa=|E|,Eba2|E|,Eca|E|不平衡負荷Unbalancedlo

adsZaZbZcMacintoshPICTimageformatisnotsupportedMacintoshPICTimageformatisnotsupportedN-N’間の電圧をEnとする各Z

に流れる電流はこれよりEnEa-En=ZaIaEb-En=ZbIbEc-En=ZcIc-En=ZnIN(7.6)Ia==(Ea-En)YaEa-EnZaIb==(Eb-En)YbEb-EnZbIc==(Ec-En)YcEc-EnZcIN=

=-EnYN(7.7)-EnZNMacintoshPICTimageformatisnotsupportedEnところで、N’において電流の総和は0であるから⚫Ia+Ib+Ic+IN=0⚫(Ea-En)Ya+(Eb-En)Yb+(Ec-En)Yc-EnYN=0⚫

En(Ya+Yb+Yc+YN)=EaYa+EbYb+EcYc∴En=(7.9)EaYa+EbYb+EcYcYa+Yb+Yc+YN非対称起電力・不平衡負荷では式(7.7),(7.9)で計算する対称・平衡

でも使える一般式中性線がなければYN=0,IN=0とするベクトル図Vectordiagram①起電力を描く通常Eaを基準②中性点間電圧Enを描く原点はN点に相当③Zに加わる電圧はEa’=Ea-En⇨Ea=En+Ea’Eb’=Eb-En⇨Eb=En+Eb’Ec’=Ec-En⇨Ec=En

+Ec’MacintoshPICTimageformatisnotsupportedMacintoshPICTimageformatisnotsupportedMacintoshPICTimageformatisnotsupp

ortedMacintoshPICTimageformatisnotsupported④線路電流を描くIa===-jaEa’ZaEa’|Za|jaEa’|Za|IaはEa’よりja遅れ大きさは|Ea’||Za|

Ea’に対して描くEnを始点とするIb,Icについても同様MacintoshPICTimageformatisnotsupportedMacintoshPICTimageformatisnotsupportedMacintoshPICTimageformatisnotsu

pportedMacintoshPICTimageformatisnotsupportedMacintoshPICTimageformatisnotsupportedMacintoshPICTimag

eformatisnotsupported例題Example[p.157]非対称Y形起電力と、不平衡Y形負荷の三相交流回路において、各線電流を求めよ。Calculateeachlinecurrentofthet

hreephasecircuitwithasymmetricalY-typepowersupplyandunbalancedloads.YN=0として、Eq.(7.9),(7.9)を使うMacintoshPICTimageformatisnotsupported中性点間電圧EnはEn=EaYa

+EbYb+EcYcYa+Yb+Yc=120(0.5-j0.4)+(-60-j80)(0.3-j0.2)+(-60+j80)(0.4+j0.3)(0.5-j0.4)+(0.3-j0.2)+(0.4+j0.3)=-8.24-j40.4=41.23

-101.3°(V)これより線路電流はIa=(Ea-En)Ya={120-(-8.24-j40.4)}(0.5-j0.4)=80.3-j31.1=86.1-21.2°(A)Ib=(Eb-En)Yb=-23.5-j1.5=2

3.5-176.4°(A)Ic=(Ec-En)Yc=-56.8+j32.6=65.5150.2°(A)ベクトル図はMacintoshPICTimageformatisnotsupportedMacintoshPICTimageforma

tisnotsupportedMacintoshPICTimageformatisnotsupportedMacintoshPICTimageformatisnotsupported演習Exercise例題において、不平衡負荷の値が図のように変わった場合の各線路電流を求め、ベク

トル図を描け。Inthepreviousexample,thevalueofloadswaschangedasshowninthefigure.Calculateeachlinecurrentanddrawvectordiagram.Macinto

shPICTimageformatisnotsupportedMacintoshPICTimageformatisnotsupported