This is the continuation of the "transformer as a generator topic"

It is a build.

The decision needs to be made on what frequency and output is required. Higher the frequency the smaller the device, and is more for battery charging. The output relates to instantaneous power consumption. My house uses 80watts and is calculated from the monthly kilowatt hour power consumption.
Water and space heating would require a different more expensive device.

The next stage is to wind some coils.

Two windings on the main transformer EI laminations 82mm x 72 x stack 30mm, 0.8mm or 1.0mm copper.  Wound 90t and 105t
Two windings on a bias transformer                             65mm x 55 x stack 22mm  0.5mm                              Wound 20% difference between turns to fill bobbin.


Ampere turns is the current times the turns of wire. 110 turns x 1 amp = 110 ampere turns. 90 turns x 1 amp = 90 ampere turns. The net result is 20 ampere turns creating the magnetic field in the transformer. To change the polarity the ampere turns are increased in the 90 turns. 1 amp would need to increase to 1.2 amps x 90 = 110 to be neutral.
To place another 20 amperes turns to reverse the magnetic polarity would take more amps. 110 + 20 = 130 and this would require 1.4 amps. An extra 0.4 amps is required to change the polarity of the magnetic field. The resonant circuit will supply most of it but an inductor is used as well. This needs to be subtle and may be over driven by three times in this example.  Remember in an eighty watt transformer the magnetic field is 1/2500th of the load, but that is without a gap in the magnetic circuit.
This device will have a few compromises the reason being to hopefully get something going in short time.

The following diagram is for a larger device. A few minor adjustments will be necessary.