"Christopher Tidy" wrote in message
oups.com...
Hi Peter,

Thanks for the advice. There's no particular reason for using
Tufnol,
except that the original (poor and broken) bobbin around the core
was
made from Tufnol. I was about to order some Tufnol tonight, but
after
hearing your comments I might not. I had also considered using PVC
or
acrylic sheet because you can buy cement which dissolves the plastic
and makes a strong bond, but both are more expensive than Tufnol. Is
SRBP easier to glue than SRBF?

The bobbin will need to fit a core with a 4" x 2.5" cross section,
have
at least a 4" length available for the winding and be no more than
4.75" in overall length. If you have anything suitable or know where
I
might buy one, please let me know. I'm also in the UK (Shropshire).

I'm winding a 240 V - 415 V autotransformer for a phase convertor.
The
core is a shell type.

Best wishes,

Chris


Chris,

When I was doing the same thing (ie autotransformer for phase
converter) I found it cheaper to buy one ready made from Power
Capacitors (the people who make Transwave converters) than buy the
bits myself. Chap even brought it to an ME exhibition and put it in
the boot of my car for me as it was the time my back was playing up!.
Neighbour is now using it for his 2 post car lift

Another way I did it when I needed a HUGE one was to get a large
240 - 240 isolating transformer that had primary and secondary 10v
and 110v tappppings - wire the primary and secondary in series and
select suitable tappings for input and output. This worked really well
as 110 worth of original primary and 110v worth of original secondary
became the input 230v so that the 415v o/p floated either side as you
want it in this application. I believe that one is still in use in a
certain canal repair yard at Dutton Dock by a certain Mr T Leech !

AWEM