Re: Modeling Constant Power Load with AC Source in LTspice
开云体育Andy, I am surprised at your response; you are typically very on point! The OP stated: “convergence failure when I run transient analysis” ? That zero crossing… ? That said, with two devices, I was having no problems with convergence: ? V: SINE(0 170 60) BI: P=if(abs(V(V))<5, 0, 500) .tran {1/30} ? Dave ? From: [email protected] <[email protected]>
On Behalf Of Andy I via groups.io
Sent: Tuesday, April 29, 2025 1:19 PM To: [email protected] Subject: EXTERNAL: Re: [LTspice] Modeling Constant Power Load with AC Source in LTspice ?
Smoother functions are almost always better, in terms of stability and avoiding instability.
What zero crossing?? If it is an .AC analysis that you're doing, there are no zero-crossings.? There are no time-varying waveforms in .AC analysis.? Signals are assumed to be single-frequency, therefore they represent the amplitudes of sine waves, but there are no sine waves anywhere in the simulation when you are doing an .AC analysis.? A "1V" sinusoidal signal in .AC analysis is represented by the quantity "1", not by a time-varying sine wave. ? That can also lead to confusion about whether a "1V" signal is an RMS level or a peak level.? The truth is that it doesn't matter.? You get to decide, as long as you are consistent about it.? If you decide that "1V" is the RMS amplitude, then everything is RMS.? If you decide that "1V" is the peak amplitude - or even peak-to-peak - then that is what it is and everything else in the simulation is measured the same way.? Because everything is strictly linear, it makes no difference.? Just be consistent about it, and you're OK. ? So -- if you think you are experiencing difficulty because of zero crossings of sine waves, you are not.? There are no sine waves in the simulation itself. ? Andy ? |
Bell, Dave