电工学武汉理工大学课件chapter5-2

电工学武汉理工大学课件chapter5-2
文本预览:

本文由漠然轻寒贡献ppt文档可能在WAP端浏览体验不佳。建议您优先选择TXT,或下载源文件到本机查看。5.4 R, L and C in series connection alternating circuit1. Relation of voltage and currentBy Kirchhoff’s Voltage Law: i uR uL uC R L Cdi 1 u = uR + uL + uC = iR + L + ∫ idt dt C u t Supposed that i = I sinωuR = RIm sinωt =URm sinωtuLmd(Im sinω ) t =L = ImωL cosω t dt= ULM sin(ω + tπuc = Xc Im sin(ωt ) = Ucm sin(ωt ) 2 2π2)πuL lead i 90° °uL = ImωLsin(ωt + 90°) = ULm sin(ωt + 90°)uc lag i 90° ° Im uC = sin(ωt 90°) = UCm sin(ωt 90°) ωC Then: URm = UR = R.ImIUL.U.ULm UL = = ωL = XL Im IUCm UC 1 = = = XC Im I ωCI.UR.UCu = uR + uL + uC =Um sin(ωt +)According to phasor diagram, voltage triangle:i i i iU ,U R ,U L + U CU = U + (UL UC )2 R 2 2 2.UL.= (IR) + (IX L IXC )2U.= I R + (XL XC)or2.I.UR UCU 2 2 = R + (XL XC) = z Iz = R + (XL XC) = U I2 2| Z | is defined as Impedance amplitude().Z = R 2 + X 2 impedance amplitudeImpedance rectangular form: is composed by | Z | 、R、(XL–XC) . 、 angel : phase difference of u and i. Phase difference is :|Z|R.XL–XCUUL + UC...URUL UC XL XC = arctg = arctg UR Rf=constant, phase difference is determined by parameters of circuit. If XL>XC, >0, u lead i , inductive circuit; If XL

第1页/共3页 下一页>尾页

寻找更多 "电工学武汉理工大学课件chapter5-2"