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Back in the 1980s, push-pull driven steel laminated inverter transformers were actually common. But technology has superseded them. However, the TS lives in a country where this technology is not available. Or prohibitively expensive.
Curious minds want to know how it is possible to drive a iron cored line frequency transformer with a PWM 15,625Hz square wave directly into the windings, and it does it with high efficiency and producing an averaged pure sine wave at nominal line frequency over its full range of loads, as an output.
Perhaps not having read the original assertions, all those who say this is a thing have given caveats on the original.
We've not yet seen the honorable members ingenious circuits schematic yet, or detailed specifications of the transformer.
Regards.
To the contrary, I have confidence that the pwm into conventional iron cored 50 Hz transformer is working well enough.
I thought back today to what I was doing 50+years ago as junior engineer developing transistor inverters.
In those days we could only do base frequency (2 pulses per cycle) as opposed to 320 pulses in present discussion.
The Ott filter was costly, moreover while it was good for Scr inverters capacitive input Z was no good for BJT.
The solution I worked on was to connect a LC parallel tank directly to secondary of the push pull transformer.
The tank had a 400V AC oil filled capacitor. Tank Q was about 5 for fuse clearing.
The switching edges on the secondary were directly applied to the capacitor.
I recall the secret sauce was to wind the inverter transformer (EI) with sufficient extra leakage L. to eliminate the AC filter input choke.
~ 4 dog bones provided the extra leakage from standard ~ 0.05pu to I suppose 0.12 pu.
I remember the collector voltage waveform, which was a replica of the tank voltage, a pure sine.
The transistor commutation rectangular pulses was superimposed. and they would get fatter and thinner doing volt regulation,
and inherently move back and forward relative to the tank voltage with load power factor changes.
However the secondary voltage was almost pure sine ( We used old HP distortion analysers)
Given that project, and the diminishing 16kHz flux swing that I mentioned in #43,
I am quite confident that an ordinary 50 Hz transformer will work with 16 kHz with today's Mosfets and their ap diodes.