Quote Originally Posted by bainbob View Post
OK, I'm getting tired of the BS from people without a clue. Microwave transformers are basically cheap junk. They have to be competitive so they cut every corner they can. Many don't even use copper wire - they use copper coated aluminum wire instead (just like the modern penny). The cores are built differently than you think. The inner cores are actually shortened so they won't contact the outer edges. They weld it just to prevent 60Hz buzzing while in operation, not because it doesn't cause an increase in eddy currents. Since the inner laminations are smaller they aren't actually welded, which helps. Google it and go read about transformers before you post a other smart-alec remark and show your ignorance. And yes, the laminates ARE insulated with paper, shellac, varnish, or something else or the huge eddy currents would cause extreme losses. Welding across the perimeter is bad but not anywhere near what uninsulated laminates would be.
Modern U S pennies are zinc alloy plated with copper. I just thought I'd take the risk. Might regret it.