12Vdc to 45VAC inverter
Back in the dark ages, I have built this kind of oscillator with 2N3055 power transistors. It is used with a 50/60Hz steel or silicon steel core transformer. 

You are going to have to use a nonlinear core model to get it to behave sensibly, because this type of oscillator depends on core saturation, but more likely it will oscillate a bit higher or lower than normal mains frequency, which typically isn't a problem. 

If you want to know the theory, this was invented in 1954 by the eponymous George Royer and you can find the original patent US2783384A here