hi Al,
The OP is trying to drive a 180Watt
resistive heating element in his caravan fridge...
Regards
Ok, thanks for pointing that out, i must have overlooked that by not
reading all the replies
Still, i think the pulse technique will be better because of the effects
on the transformer that is probably designed for AC like 50 or 60Hz.
Since it is going to drive a resistive load (only) i think i would raise
the frequency up to maybe 100 or 120Hz, and then a square wave
would probably be ok. In fact, i might go as high as 200Hz, at least
to try anyway. The only drawback i can think of at the moment is
the audio noise that may come out of the transformer...this would
depend on the transformer and just how perfect the square wave
was as compared to a perfect 50 percent duty cycle. Losses
will be a little higher at 120Hz, but at least the transformer
would be operating more comfortably (not near saturation).
I dont know exactly what the core is made of, so i wont say
too much about this, but it does sound like it's ordinary EI
low ac frequency laminations (50 or 60Hz).