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Copper wire primary and Iron wire secondary,what type of wave form will the transfomer have

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Andy

Tue Dec 31 2013, 04:31AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Hi, being thinking about this awhile, if you have a transformer with copper primary and iron secondary's, at high hertz, what would the effect of the wave form be as iron has some retention.

Cheers
Andy

Mattski

Tue Dec 31 2013, 07:45AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

Iron wire will have a higher inductance and resistance than copper wire in the same geometry, plus probably some eddy current loss, so you'll get a lower secondary resonant frequency and more damping.

Sulaiman

Tue Dec 31 2013, 09:52AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

An interesting question,
the high permeability of iron will have significant effects;

skin effect will be very strong causing the already relatively high resistance will become much higher
(depending upon frequency) so the secondary resistance will be very high.

as above, eddy currents in the wire will cause excessive heating in the iron wire

the iron may form a partial magnetic shunt causing much lower secondary voltage.

iron, being brittle , may fracture due to the vibrations caused by the alternating forces

overall, not a good idea to use iron wire.

Proud Mary

Tue Dec 31 2013, 05:27PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Still, the idea isn't totally daft when one recalls the inductive loading of submarine cables with Permalloy and Mu Metal in order to meet the Heaviside Condition until the 1930s. Not good for transformers, but a good question to ask!

Ash Small

Tue Dec 31 2013, 05:54PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

If youhave some iron wire and you want a use for it, you can dip it in enamel or whatever, then use a bunch for a transformer core. If you leave the wire long enough to wrap around the windings, it greatly improves the coupling (reduces stray/leakage inductance). The insulated wires reduce eddy currents to a minimum.

At least, I'm reasonably certain this is all correct.

Proud Mary

Tue Dec 31 2013, 06:06PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Ash Small wrote ...

If youhave some iron wire and you want a use for it, you can dip it in enamel or whatever, then use a bunch for a transformer core. If you leave the wire long enough to wrap around the windings, it greatly improves the coupling (reduces stray/leakage inductance). The insulated wires reduce eddy currents to a minimum.

At least, I'm reasonably certain this is all correct.

Annealed iron wire was used in the cores of Victorian induction coils: e.g. this patent of 1893

Added afterthought I am completely clear on the extremely slow annealing process from bright orange to room temperature, but how does one keep the wires straight and parallel when forming them into a bundle?

Andy

Wed Jan 01 2014, 03:14AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

The book that made me think about this in the inductor section had me thinking that a coil with alot of inner turns of copper wire, and larger gauge iron wire on the outside would make more of a inductive kick, as the copper should collapse quickly with the iron adding about 100 times the field lines with self induction boosted, maybe have the layers alternating.
The same theory would happen in a transformer.

Strange setup or might it work.

Ash Small

Wed Jan 01 2014, 10:32AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Proud Mary wrote ...

Added afterthought I am completely clear on the extremely slow annealing process from bright orange to room temperature, but how does one keep the wires straight and parallel when forming them into a bundle?

You can straighten them by rolling between two boards:

(article starts on page 57,)

Proud Mary

Wed Jan 01 2014, 11:25AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Ash Small wrote ...

You can straighten them by rolling between two boards:

(article starts on page 57,)

Brilliant stuff, Mr Ash! I love antique radio books and magazines that tell you how to make everything from scratch with simple tools.

Ash Small

Wed Jan 01 2014, 11:50AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Proud Mary wrote ...

Ash Small wrote ...

You can straighten them by rolling between two boards:

(article starts on page 57,)

And the first copy of Radio News, from July 1919 is here:

Brilliant stuff, Mr Ash! I love antique radio books and magazines that tell you how to make everything from scratch with simple tools.

Me too. I think there are more of those, but I've not explored the whole site yet. Apparently you don't need a 'step up' interstage transformer when using valves from the mid-thirties onwards, as valve technology moved on quite significantly.

EDIT: Here's the 'main' page:

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