transformer core

[Kevin Weddle]

What is something that I can use for a transformer core? A piece of
steel that has a large area is what I think I need. Do I have to find
a steel shop? The example core that I have seen has a large area as
opposed to just length.

 

[Robert Baer]

What is something that I can use for a transformer core? A piece of
steel that has a large area is what I think I need. Do I have to find
a steel shop? The example core that I have seen has a large area as
opposed to just length.

It is not "ordinary" steel; it is a special alloy.
One can get surplus transformers with sufficent window area for
proposed windings, and use the laminations from two or three same-sized
transformers to build a larger power transformer than what is otherwise
available.
And do you know how much power the proposed transformer must handle,
so that youcan calculate the required cross-sectional area?
And then, calculate the number of turns per volt?

 

[Kevin Weddle]

It is not "ordinary" steel; it is a special alloy.
One can get surplus transformers with sufficent window area for
proposed windings, and use the laminations from two or three same-sized
transformers to build a larger power transformer than what is otherwise
available.
And do you know how much power the proposed transformer must handle,
so that youcan calculate the required cross-sectional area?
And then, calculate the number of turns per volt?

I understand that the winding itself should be able to handle the
current. But if a coils core is too small, the current will destroy
the winding?

 

[Robert Baer]

I understand that the winding itself should be able to handle the
current. But if a coils core is too small, the current will destroy
the winding?

Getting the proper wire size is simple and not related to power level.
If one draws an excessive current, then one or more windings get hot
and can cause a small fire.
If the current is really large, hopefully the mains fuse or circuit
breaker will act as protection.
Then again, one time someone plugged a "short circuit" into a 110V
outlet, and a flame shot out 2-3 feet for well over 15 minutes, and the
15 amp circuit breaker did not even think of tripping.
That half of the outlet was turned very black, and all of the copper
there was vaporized (top half almost completely intact).
I am guessing the arc current was a mere 10-12 amps...

 

[Bill Vajk]

Getting the proper wire size is simple and not related to power level.
If one draws an excessive current, then one or more windings get hot
and can cause a small fire.
If the current is really large, hopefully the mains fuse or circuit
breaker will act as protection.
Then again, one time someone plugged a "short circuit" into a 110V
outlet, and a flame shot out 2-3 feet for well over 15 minutes, and the
15 amp circuit breaker did not even think of tripping.
That half of the outlet was turned very black, and all of the copper
there was vaporized (top half almost completely intact).
I am guessing the arc current was a mere 10-12 amps...

Failure to trip is common in some brands. Federal Pacific bribed their
UL approval for decades (well documented in the press at the time it
was discovered.) I've personally experienced failure to trip in FP
breakers at sometimes 6 to 7 times the rated current.

In addition, as inexepnsive as the typical circuit breaker is, they're
just not all that reliable. If you absolutely positively *must* have
reliability, stick to fuses.

 

[Robert Baer]

Failure to trip is common in some brands. Federal Pacific bribed their
UL approval for decades (well documented in the press at the time it
was discovered.) I've personally experienced failure to trip in FP
breakers at sometimes 6 to 7 times the rated current.

In addition, as inexepnsive as the typical circuit breaker is, they're
just not all that reliable. If you absolutely positively *must* have
reliability, stick to fuses.

I agree on the reliability statement.

 

[Bill Vajk]

Bill Vajk wrote:

I agree on the reliability statement.

Here's some more info:

http://www.inspect-ny.com/fpe/CPSCsummary.htm

Also you can google "federal pacific" UL

(don't forget the double quotes) and get some 227 hits.

My 6 to 7X current was on a 20 amp single pole FP breaker.