I have a question about the magnetizing current in a forward switching converter (image from "ON Semiconductor: Am improved 2-switch forward converter application").
From the picture it looks like there is a finite current in the primary, when the switch Q1 is off. My question is, how is that possible, since the primary is made out of a single wire ? How can you physically have a current in an open wire ?
That picture is incorrect for anything other than what it is intended for i.e. to demonstrate that you need to reset the flux in an inductor or transformer.
What happens in reality with the circuit shown is that the energy built up (by the rising current) creates a high voltage when the MOSFET turns off and destroys it. They are using this circuit as a "device" to explain the problem.
If you'd shown the full picture and read the subsequent pages you might have made more sense of it: -
