* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download doc00000 - Finite Element Method Magnetics
Electrical substation wikipedia , lookup
History of electromagnetic theory wikipedia , lookup
Ground loop (electricity) wikipedia , lookup
Electric power system wikipedia , lookup
War of the currents wikipedia , lookup
Transmission line loudspeaker wikipedia , lookup
History of electric power transmission wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Voltage optimisation wikipedia , lookup
Ground (electricity) wikipedia , lookup
Opto-isolator wikipedia , lookup
Electric machine wikipedia , lookup
Mercury-arc valve wikipedia , lookup
Current source wikipedia , lookup
Stray voltage wikipedia , lookup
Magnetic core wikipedia , lookup
Loudspeaker enclosure wikipedia , lookup
Rectiverter wikipedia , lookup
Mains electricity wikipedia , lookup
Earthing system wikipedia , lookup
Aluminium-conductor steel-reinforced cable wikipedia , lookup
Transmission tower wikipedia , lookup
Buck converter wikipedia , lookup
Three-phase electric power wikipedia , lookup
Electrical wiring wikipedia , lookup
I am using “Finite Element Method Magnetics” programs for calculation of eddy current losses in enclosure of three-phase segregated and nonsegregated busbars. Thanks to you, until now I have successfully calculated losses in enclosure for several configuration of busbars. In FEMM Users Manual you said that for bulk coils ( in my case they carry currents J src) conductivity of zero should be defined. In that case I could calculate only a eddy current losses in enclosure, and losses in conductors are zero. Since the equation that FEMM actually solves for planar (2D) problems is: 2 A 2 A jA J src x 2 y 2 (1) and this is the same as: 2 A 2 A jA U x 2 y 2 (2) where U=Jsrc, and U is the voltage applied to a conductor in which skin effect is to be calculated. (Equation (2) was taken from “Teoretska elektrotehnika” by Z. Haznadar) If I define a nonzero conductivity for conductors (bulk coils) and define such voltage which will give the real value of current through the conductors, I could actually calculate resistive losses or skin effect factor in conductors as kskin=Pac/Pdc, where Pac are resistive losses for alternating current, and Pdc losses for direct current. To get the real current through the conductors (real amplitude and phase, for example: for three phase current i1=Icost, i2=Icos(t+120), i3=Icos(t-120) or as phasor i1=I+j0, i2=-0.5I+j0.866I, i3=-0.5Ij0.866I, where I is amplitude of sinusoidal time varying current) I must do several iterations. When I achieve real values of currents through the conductors then I can calculate losses in conductors and losses in enclosure. I made several calculations with and without taking in consideration skin effect in conductors. In both cases the eddy current losses in enclosure was the same. I also made several calculations of skin effect in conductors (without enclosure). For two parallel Al conductors 100x10 mm on distance 30 mm through which alternating (in first calculation) and direct (in second calculation) current of 200A flows, I obtained k skin=1.22. For the same conductors in some books I found kskin=1.19 and in others kskin=1.23. The difference probably happened because electrical conductivity of Al used in my calculation was little different than those used in other Literature. Is it possible to calculate losses in conductors for alternating current in this way using FEMM? In all of my calculations I used Dirichlet boundary condition. Figure below shows cross section of three-phase nonsegregated busbar and boundaries of problem. Boundary (Dirichlet) Al enclosure 900 Cu conductors 4 80 500 6 10 250 250 200 Example of cross section of three-phase nonsegregated busbar (All boundaries are Dirichlet, A=0 ).