SINE Wave in LTSpice

HI TV1 ,

Shot in the dark here. My guess is that your calculations are for a Vp-p (peak to peak) of 177V, whereas LTspice defines sine via Vp (peak). In LTspice, set the amplitude to Vp of 88.5.

The parameters are defined in Help. 

mike

Thanks Mike! The amplitude is correct, 177Vp. This is the peak voltage of the household 120Vrms, 60 Hz line. The issue appears to be related to settling time, it takes about 3 s for the current to come to a steady state of ~ 12 A. My .tran setting was limited to 100ms.  I need to look at the circuit more closely to understand it. See the results below. 

Hi TV1 ,

seems like your computation in the above concern is for the steady state of the response. The simulation shows you even the start up condition.

You can skip this condition by specifying where you would like to start saving data and it shall show you only the steady state condition.

Here, I added a 4s skip to show only the steady state response, showing the exptected ~12A.

Best Regards

Earl

Thanks Earl - yes, I noticed that when I extended the .tran directive beyond 100 ms and, as noted, steady state begins at approximately 3-4 s. I just need to better understand the decaying offest at start-up. Thanks for the Info, Tony

Hi TV1 ,

Yes, I also noticed the decay to settle. Never ran it long enough to see full settling, but figured it would. I'm also curious about what is going on. I wonder if you would see the same on the bench top, though startup conditions are likely very different IRL.

BTW, you can use .savestate and .loadstate to save the settled state and come back to it later.

mike

Thanks, Mike, for the save and load state commands.

I have a question about transformer modeling. I used two inductors and used the K directive to couple the inductors; however, the phase dots are not displayed. When I tried to enable them in the L1, L2 models, the 'Show Phase Dot' options are grayed out. See the screen shots of the L1, L2 model parameters and the schematic symbol, which is missing the dots on L1, L2. I can determine where the dots are located by using the measure current icon to view the direction of current measurement.

Note that 'Show Phase Dot' is grayed out for both L1 and L2: