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Problem with simulationby rf74
Tags: simulation 
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#1
Apr914, 10:48 AM

P: 5

Hi,
I have a problem with my simulation (Multisim). I don't find the error. Voltage and current increase very high in a short time. It's only 3 selfs with coefficient at 0.9 for L1/L2 and for L2/L3. K is at 0 for L1/L3. I give image for the circuit and the result of simulation. The problem come from K ? K1 LL1 LL2 0.9 K2 LL2 LL3 0.9 thanks 


#2
Apr1114, 02:01 AM

P: 5

Hi,
Someone can help me ? I don't find my error. If I'm looking at energy input/output, the sum is no 0. I simulated with R1 and R2 at 1 MOhm but the circuit give high voltage. If K1 and K2 are under 0.5 it's ok, but with K1=K2=0.9 and K3=0, voltages at R1/R2 increase very high. I tested with another software and it's the same result. K1 LL1 LL2 0.9 K2 LL2 LL3 0.9 K3 LL1 LL3 0.0001 or 0 


#3
Apr1614, 06:52 AM

P: 5

Hi,
I found the problem, it's because I let K3=0, I can't do that, the minimum must be at K1K2. I find a circuit where I can have a single sign current from a sinusoidal source, and the sum of energy is not zero. But is it possible in a self to have a positive current ? I give you the circuit, I tested with Multisim and LTSpice, it's the same result. 


#4
Apr1714, 03:27 AM

P: 5

Problem with simulation
Hi,
I simplify the circuit, it can be like: vV3 14 9 dc 0 ac 1 0 + sin(0 {90*1.414213562} 60 0 0 60) vV2 0 6 dc 0 ac 1 0 + sin(0 {90*1.414213562} 60 0 0 60) rR4 11 4 1 K2 LL2 LL3 0.9 rR2 10 9 1 lL3 13 0 1 lL2 5 0 1 There is a positive current in transformer, the energy from the source is +V*I V*I in a period, like I is always positive, the energy from source is 0. Like that it's logical, but energy must be conserved so it is a problem from Spice, the current at start is not like that in reality ? I think it could like that at start with an external DC source no ? I tested with Multisim and LTSpice. The difference of energy is 1200 J in a second. This is only in the transitive time. After current is at 0, no energy at output and no energy at input. If K=1 the energy is conserved, it's only when I let K=0.9 or 0.5. Angle phase must be at 60° for example, don't let it at 0°. Someone can test for verify my study ? It is the energy inside 1/2LIČ ? At start I=110A so the energy inside selfs is LIČ=121kJ. If I let: vV3 14 9 dc 0 ac 1 0 + sin(0 {90*1.414213562} 60 0 0 60) *## Multisim Component V2 ##* vV2 0 6 dc 0 ac 1 0 + sin(0 {90*1.414213562} 60 0 0 240) The energy at outputisnot the same. Thanks for your help 


#5
Apr2014, 06:16 AM

P: 5

Hi,
I understood, it's because the energy is inside inductances ! Software give start values for current and there is energy inside inductances. All is fine ! bye 


#6
Apr2014, 10:27 AM

Sci Advisor
Thanks
PF Gold
P: 12,257

Well done rf74. You constructed a whole, satisfactory thread with question, discussion and answer, all by your self!
In the old days, before the Internet, this was how we all used to solve problems. lol 


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