I bought this transformer https://www.mouser.com/ds/2/410/media-1067263.pdf
I connected the primary in parallel for 115v and the secondary in parallel for 115v but it instantly blows the 6A fuse.
A series connection on the output works fine, but only if it is not connected to anything other than my meter. Even connecting it to a rectifier with nothing connected to its output blows the fuse when wired in series.
I don't know what is happening. I did not miswire it according to the datasheet.
Any advice?

 

Hello,

Does the fuse also blow when you leave the secondairy windings open?
It sounds like a misconnection to me.

The colors are clearly given in the datasheet:
Input 1: Series – BLUE and BROWN, Jumper GRAY to VIOLET
Parallel – BLUE and BROWN, Jumper BLUE to VIOLET, GRAY to BROWN
Output1: Series – BLACK and YELLOW, Jumper RED to ORANGE
Parallel – BLACK and YELLOW, Jumper BLACK to ORANGE, RED to YELLOW

Bertus

 

If the wiring is OK then maybe it's your fuse?

Toriodal transfomers in my experience can pull quite a large current peak on connecting the mains. Are you using a slow blo 'T' type fuse?

 

If the wiring is OK then maybe it's your fuse?

Toriodal transfomers in my experience can pull quite a large current peak on connecting the mains. Are you using a slow blo 'T' type fuse?

I am willing to bet this is exactly the cause. I have also experienced that torroidal transformers have very high inrush current. You need to use very slow fuses with them. Maybe a motor starter would be a good protection device for them.

 

Or maybe an inrush current limiter.
SG