Anyway to check my math for these kind of circuits with LTSpice?
Your 3 Phase Sources are OK, whats the tutors question .?I don't know if what I've done is even close to be correct.
Well, the original problem has no C and L values. It only has Xc and Xl.Your 3 Phase Sources are OK, whats the tutors question .?
E
I have used MatLab but in a very light way. I also have Octave installed in my Linux OS.Your answers look fine.
The problems with using a simulation to check your results include:
1. Accuracy errors.
2. Difficulty of resolving phase relationships.
Why don't you simply trust your answers & confirm them by mathematical means - such as plugging values back into the circuit to confirm agreement with Kirchoff's laws. Do you use applications such as Matlab which can make the mathematical manipulations more robust?
While I could provide that information, I think in the interests of adhering to the homework forum rules as well as for your own benefit, that you need to put in some effort.
The answers you gave for the problem were very accurate and presumably machine (rather than hand + calculator) generated - so you must have a good idea of how to attack problems requiring the efficient & accurate solution of simultaneous equations with three or more unknowns.
Matlab and the Matlab clones are great for the aforementioned task where matrix operations can be effectively applied to problems such as the one at hand.
I understand your rationale for wanting to use simulation to verify your problem solutions. Personally I'm not sure LTSpice is the greatest option, notwithstanding the fact that it is free for personal use. I use an application called PSIM for 3-phase & other power electronic simulation work. A demo version is available for free here:
http://powersimtech.com/products/psim/
If you are looking to a career in electronics or electrical engineering then you may need to develop familiarity with a broad range of simulation software tools which target particular areas of electronics or electrical engineering.
A cautionary note: Simulation is no substitute for practical work experience, disciplined critical reasoning & hard work.
If I consider the counter-clockwise rotation phase, "I think I get" the following:Uc = 380V
380/sqrt 3 = ~220V
Uac = 220|0º
Ucb = 220|-120º
Uba = 220|120º
I'll consider the following:
Ua = 380|30º
Ub = 380|-90º
Uc = 380|150º
So, each phase's impedance will beXL = 2*∏*50*0.1 = 31.42jΩ
Now I can calculate phase current by:Z = 10 + 31.42j Ω.
Iac=V/Z <=> I=380|30º/(10+31.42j)=11.52|-42.4ºA
With these currents I can calculate Iam, Ibm and Icm by the Nodes Law.Ica = 11.52|-42.3ºA
Ibc = 11.52|-162.3A or 11.52|197.7A (my calculator finds the positive angle version when the calc returns a negative angle. I mean, -162.3+360=197.7)
Iab = 11.52|77.7A
Node A at the triangle right side: said:Iam + Ica = Iba <=> Iam = Iba - Ica <=> Iam = 11.52|77.7A - 11.52|-42.3A = 20|107.7ºA
Node B at the top of the triangle: said:Ibm + Iab = Ibc <=> Ibm = Ibc - Iab <=> Ibm = 11.52|-162.3A-11.52|77.7A = 20|227.7ºA or 20|-132.3A
=======================Stage 3====================Node C at the right side of the triangle: said:Icm + Ibc = Ica <=> Icm = Ica - Ibc <=> Icm = 11.52|-42.3A-11.52|-162.3A = 20|-12.3ºA
As we are said that the system is "balanced", all 3 resistances are equal, soPtotal = 50x60=3000W
Pphase = Ptotal/3 <=> Pphase = 1000W
Pphase = Vphase*Iphase*cosδ <=> 1000 = 220*Iphase*cos 0º <=> Iphase = 4.55A
I have another question here:updated said:Ial = 4.55|0ºA
Ibl = 4.55|120ºA
Icl = 4.55|-120ºA
Ia = Ial + Iam <=> Ia = 19|94.6ºA
Ib = Ibl + Ibm <=> Ib = 19|214.6A
Ic = Icl + Icm <=> Ic = 19|-25.4A
hi,My first question comes now. Is it the Simple Voltages that has the 0º, -120º and 120º or is it the Line Voltages or is it the same no matter which ones I choose to have the 0º, -120º and 120º angles?
by Jake Hertz
by Jake Hertz
by Aaron Carman
by Jake Hertz