current - My first transformer causing safe fuse to go out

I found a fairly big, old transformer. I unwinded all the coils and winded them again. My primary coil has 20 turns, and the secondary coil has 200 turns. I didn't use any tools while doing this, so it isn't precisely woud.

Now, when connecting this transformer directly into the power outlet, the power fuse goes out. I have 3 theories for why this is happening:

1. Maybe I shouldn't connect the transformer directly into the outlet - do I need to put something "in between" the transformer and the power outlet?


2. Maybe I am connecting the transformer in a wrong way? Currently I connect it by putting first primary coil wire into first hole in my power outlet, and second primary coil wire into second outlet hole.


3. Is it possible that there is something wrong with the wires? I put isolation tape all over the primary coil so that those two won't touch.

What is wrong with my transformer?