No, that gives you apparent power as I keep saying. You need to adjust for any phase angle displacement of current with respect to voltage to get true power.
I know you keep saying that, but I still don't understand it. By "instantaneous" I mean "in that given instant"...
A transformer primary exhibits both magnetizing and leakage inductances and current lags voltage in an inductor, right?
It doesn't matter what the voltage waveform applied to the primary of a transformer looks like, the current through it will be a time (phase angle) delayed version of it*. * - EDIT - and integrated... forgot that part.
In a lossless transformer with finite magnetizing inductance and the secondary unloaded, the only current flowing in the primary will be for magnetizing the core and this is a purely inductive current so it will be phase shifted by 90 degrees from the voltage. This is a measurable current and the voltage is of course also measurable, but if you simply multiplied those two parameters together without accounting for the phase shift you get apparent power, VA, not real power, W. To find real power you have to multiple VA by the cosine of the phase angle displacement which in this case is 0.
If this "almost ideal" transformer is loaded on the secondary, the primary current will increase - because of the current reflected from the secondary through the turns ratio - and the phase shift will decrease, because the magnetizing current with its 90 degree phase shift will become a progressively smaller fraction of the total primary current. In a real transformer there are both iron and copper losses, of course, and the iron losses will be fixed for a given applied primary volt*seconds while the copper losses will vary with the square of load current. Hence why I said that actually measuring the efficiency of a transformer is tedious and not typically worth the bother.
This applies whether the transformer is driven by a sine wave from the mains or a square wave from an H-bridge.
And in this case the transformer is driven by a exponential decaying pulse.
Doesn't matter.
I sure sense your frustration all the way across the pond. If you look at the graph in my OP you can see the voltages and currents involved. And I couldn't very well calculate average power before I there were some agreement to how it should be done.
Pictures accompanying a post should help illustrate what is written, not substitute for it. Look at all the forums - including this one - where images were hosted on Photobucket or the like and are now no longer available. IMO, it's better to present too much information in the OP than to trickle out details in subsequent replies.
If it was only a question of shame, I would certainly do that, in fact I would outsource everything.
You may have misinterpreted me. I could certainly design your transformer but I almost certainly couldn't make it myself - not even a prototype. Thus I would specify the core size and material, number of primary and secondary turns, wire gauges for each, layer stackup and other pertinent details like what UL or EN classification it needs to meet, vacuum impregnation, etc., and then let the transformer manufacturer worry about the rest... like how to wind thick ribbons of copper around the coil former or achieve a 10kV or so functional insulation level.