opto-isolatorpower supplytransformer
If I obtain the iron core from a microwave oven transformer and strip off all the windings then wind 2 coils, each being 20 turns with 12 gauge wire, will I effectively have made an isolation transformer?
Can I use it with household power without tripping the circuit breaker?
What do I need to do to make sure to not trip the circuit breaker?
Due to an error in my calculations, the transformer's impedance was way too low, allowing a large amount of current to flow.
Here (from Wikipedia) is a fairly complete linear model of a transformer:
Note the magnetizing inductance Xm across the primary. If that inductance is too low, you'll get excessive current flowing even with no load on the secondary.
While a single-turn primary is certainly possible, with sensibly-sized cores it implies either a very low voltage (for example, a current transformer, which is typically toroidal) or a very high frequency (or both).
The inductance is proportional to the number of turns squared, and a small 120/240V 50/60Hz mains transformer primary might be some hundreds of turns, so you can see how far off a single turn is. At a fraction of a volt, or higher frequencies at relatively low voltage, a single-turn primary might make some sense.
Best Answer
Yes, assuming the wire is insulated from itself and adequate creepage and insulation thickness and breakdown rating (for your purposes) is provided between primary and secondary windings. With 20 turns it will only be useful for low voltage AC.
No, it will smoke and/or blow the breaker.
Wind enough turns to reduce the magnetizing current to a reasonable value. That will likely be at least as many as were there originally on the primary for whatever your mains voltage is. The magnetizing current is proportional to the reciprocal of the square of the number of turns.