Transformer simulation with LtSpice

Hi Folks,

I've been playing with LTspice simulation and done coorelation with basic lab equipment with some help form the expert on this forum. It been a while since I have a chance to review this basic stuff. This is very useful.

I'm stuck with one issues. I attached 2 file here. One result is from AC Analysis and another is from Transient Analysis. I did the transformer simulation using 2 method, one is using LTspice coupled transformer model and another is using a T model calculated from transformer datasheet.

On Ac analysis, the result are as I expect for both method and quite coorelate between the 2 models.
On Transient analysis, result from coupled inductor method seem to look ok but the one with T-Model are strange. Can anyone explain why I got this result when I use the T-model. I've a feeling that I probably missing something very easy.

BTW, I've another few questions with LTspice if someone happen to know the answer.
-How to attached the cursor to the phase plot in AC analysis?
-Is there a way to save plot and reload it later? I want to be able to see the result of transient analysis and AC analysis at the same time.

TIA,

kudjung said:

...
On Ac analysis, the result are as I expect for both method and quite coorelate between the 2 models.
On Transient analysis, result from coupled inductor method seem to look ok but the one with T-Model are strange. Can anyone explain why I got this result when I use the T-model. I've a feeling that I probably missing something very easy.

Click to expand...

Yes, type mismatch on L1 (a negative value)

BTW, I've another few questions with LTspice if someone happen to know the answer.
-How to attached the cursor to the phase plot in AC analysis?
-Is there a way to save plot and reload it later? I want to be able to see the result of transient analysis and AC analysis at the same time.

Click to expand...

the cursor can be attached to the phase plot by clicking the label different cursor can be selected by left click on the label.
and about saving polt there is option of save imageas ,use this option to save the plots

Sorry, I'm very new with LtSpice. What should I do with that negative value inductor? That's the value I got translating form transformer datasheet.

---------- Post added at 10:48 ---------- Previous post was at 10:42 ----------

fareen said:

the cursor can be attached to the phase plot by clicking the label different cursor can be selected by left click on the label.
and about saving polt there is option of save imageas ,use this option to save the plots

Click to expand...

Hi Fareen,

Is there any other format that we can open a saved plot using LTspice? I want to review some of the plot at the same time on Ltspice itself so that I can have cursor.

I my opinion, this isn't a reasonable transformer equivalent circuit. The coupled inductors circuit can represent transformer ratios, the T-circuit can't. It has to refer to negative inductances, that LTSpice apparently doesn't like. Honestly, I'm not motivated to find out why. You better use a physically plausible equivalent circuit instead.

P.S.: You can review previous analysis results by opening the respective *.raw files. Not sure, if this is what you intend.

Is there any other format that we can open a saved plot using LTspice? I want to review some of the plot at the same time on Ltspice itself so that I can have cursor.

Click to expand...

i didnt understand your question??
i think you are asking if we can open plot of other format not ltspice
so the answer is no.but youcan open more than one plot in ltspice .for example if you are working on a circuit and you want to see its transient response and frequency response at the same time than you will have to make the copy of the circuit open new tab and then see the plot
i hope you get i

Ok,Understood your point.

---------- Post added at 04:51 ---------- Previous post was at 04:48 ----------

fareen said:

i didnt understand your question??
i think you are asking if we can open plot of other format not ltspice
so the answer is no.but youcan open more than one plot in ltspice .for example if you are working on a circuit and you want to see its transient response and frequency response at the same time than you will have to make the copy of the circuit open new tab and then see the plot
i hope you get i

Click to expand...

Look like there's no way to save only the plot itself then. I need to make a copy of the entire project and re-configure that to compare the result.

Got it,Thanks!

Look like there's no way to save only the plot itself then.

Click to expand...

I don't agree. If you keep both the raw data and plot settings file, you can reopen the plot without making additional settings. The raw data files contains all analysis data, but you have to perform add trace to show the results.