Background: I need a transformer that can supply 6.3V (+/-1%, as per the heater's specs) and 25 A for a heater.
As a result, I decided to hack a MOT by breaking off the bottom laminations and removing the coils.
The plan is to use a variac (0-130 VAC, 1 kW max.) that will plug into a US standard single phase outlet (110-120 VAC, 50/60 Hz). The output of the variac will lead to the primary windings of the MOT.
For reference, the MOT core has a depth of 2 inches, a width of 3.5 inches, and a height of 3 inches.
For my application, I rewound the MOT such that the primary is made up of 17 turns of 18 AWG wire insulated for 300 VAC. The secondary is comprised of a single turn of 8 AWG wire. Both the primary and the secondary take up an equal length of the MOT core.
Since the bottom of the core was broken off, it is currently a bit loose but is attached to the rest of the core via gravity.
I used a zip tie to provide a 1 cm gap between the primary and secondary windings.
Here are a few pictures of the set up for reference:
Question: Will this set up allow for me to produce a sufficient voltage (assuming I set the variac to around 107 VAC) and 25-30 A?
Best Answer
no, that setup will not produce enough voltage (at mains frequency)
at mains frequency microwave oven transformers saturate at about 1 turn per volt, so you want a secondary with more than 6 turns.
Put the original primary back onto your transformer, and add 7 to 10 turns of thick copper wire, or magnet-wire "rope" for the secondary