I have this circuit that I'm going to build, including the transformer. It is a simple power supply, with RC filters and one choke, I know all the voltages and currents.
Because I will design, wind and build the transformer myself (I already know all of that as well) I need to know the VAs that it must withstand.
I know that the total current load pulled from the transformer will be more than just the sum of all the DC sources because the capacitors pull reactive power that is not "used" by the circuit itself but just shuffled back and forth to keep the voltages at the nodes clean and constant.
I also know from past experience, that to find the VAs, it is not as simple as just multiplying the rms AC voltage (green, 358VAC) and the rms current flowing through the transformer (red, 1.21A) because the shape of the waveform as well as phase has a lot to do with it. The AC voltage is a sinewave, but the AC current flowing through the winding of the transformer (L2) has spikes. For example, if I just multiply both values I get ~433VA which is a lot more than I would expect.
So, the solution is to ask LTSpice to do the work for me and ask it to plot a graph of the power consumed (pink). The problem is that it shows the average value, not the rms, and there is the dilemma. Are those 144W average the VAs that the transformer will be working with and thus, the figure I have to design the transformer around? If not, how can I calculate or approximate the RMS value from that AVG value?
EDIT: This circuit is the power supply for a 50W vacuum tube amplifier I'm designing. The power consumption of a commercial amplifier that puts out 120W is claimed to be 300W, so the reading LTSpice is giving me does make sense, it is a little higher still considering that the transformer will have more windings that will draw an extra of about 35W in total, but that's because efficiency overall decreases with power, so the 144W is in the ballpark, I just want to confirm it.