toroidial transformer winding question

[[email protected]]

I have several toroidial transformers that have two 115v windings and
two 25v windings on each. The way I understand electricity each 115v
winding would only go 1/2 way around the toroid then the 25v winding is
on top of that winding is this correct? or do both windings go all the
way around? that would be more of a 1:1 isolation transformer (if the
25v windings were gone) Am I thinking correctly? Thanks Res.

 

[Rich Grise]

I have several toroidial transformers that have two 115v windings and
two 25v windings on each. The way I understand electricity each 115v
winding would only go 1/2 way around the toroid then the 25v winding is
on top of that winding is this correct? or do both windings go all the
way around? that would be more of a 1:1 isolation transformer (if the
25v windings were gone) Am I thinking correctly? Thanks Res.

They're isolated electrically, just because the wires are insulated. The
thing that would change with the different winding patterns would be
interwinding capacitance and possibly the mutual inductance, or the
magnetic coupling between the windings, which would only affect
effeciency.

Hope This Helps!
Rich

 

[Bob Eld]

I have several toroidial transformers that have two 115v windings and
two 25v windings on each. The way I understand electricity each 115v
winding would only go 1/2 way around the toroid then the 25v winding is
on top of that winding is this correct? or do both windings go all the
way around? that would be more of a 1:1 isolation transformer (if the
25v windings were gone) Am I thinking correctly? Thanks Res.

You are not thinking correctly. Any winding or windings can be primary(s) or
secondary(s). It does not matter where on the core they are wound except for
issues like capacitace and leakage inductance. All windings should cover as
much of the core as possible depending on the number of turns and the wire
thickness. Each 115 winding may go more or less than half way or they may go
more than one complete layer, again depending on the turns required. It is
possible that the two 115 windings are in three or four layers. It is not
knowable with the information provided. If you provide the physical size of
the transformer(s) the power level and frequency, typical windings can be
estimated, both number of turns and wire size. Of course there are other
factors complicating the issue such as allowable temp rise, maximum flux
density, allowable leakage flux, maximum inrush current, necessary
magnetizing current, efficiency, acoustic noise, allowable waveform
distortion, creepage distance and other factors that can complicate a real
design.
Bob

 

[John Larkin]

I have several toroidial transformers that have two 115v windings and
two 25v windings on each. The way I understand electricity each 115v
winding would only go 1/2 way around the toroid then the 25v winding is
on top of that winding is this correct? or do both windings go all the
way around? that would be more of a 1:1 isolation transformer (if the
25v windings were gone) Am I thinking correctly? Thanks Res.

Usually one winding is wound, pretty much evenly all around the core,
making the donut fatter. A layer of insulating tape goes next, then
the next winding, also more-or-less evenly distributed around the
core. And so on.

Yes, the two 115v windings can be used to make an isolation
transformer.

John

 

[Phil Allison]

<[email protected]

I have several toroidial transformers that have two 115v windings and
two 25v windings on each. The way I understand electricity each 115v
winding would only go 1/2 way around the toroid then the 25v winding is
on top of that winding is this correct?

** No.

All the winding go fully around the toroidal core.

The primaries are wound first then the secondaries wound over the top.

The two 115 volts windings are insulated from each other, but with not as
much polyester wrap as the secondary to primary insulation.



........ Phil

 

[Jasen Betts]

I have several toroidial transformers that have two 115v windings and
two 25v windings on each. The way I understand electricity each 115v
winding would only go 1/2 way around the toroid then the 25v winding is
on top of that winding is this correct? or do both windings go all the
way around? that would be more of a 1:1 isolation transformer (if the
25v windings were gone) Am I thinking correctly? Thanks Res.

the insulation between thhe two 115V winding s may not be as good as
between the 115 and 25V windings.

to make an isolating transformer hook the 25 windings of wto of your several
transformers together (in parallel) and feed 115V in one end and you'll get
most of it out the other end.

Bye.
Jasen

 

[Pooh Bear]

Usually one winding is wound, pretty much evenly all around the core,
making the donut fatter. A layer of insulating tape goes next, then
the next winding, also more-or-less evenly distributed around the
core. And so on.

Yes, the two 115v windings can be used to make an isolation
transformer.

You can't legally use it that way for isolation since the insulation doesn't
meet safety regs.

Graham

 

[Pooh Bear]

the insulation between thhe two 115V winding s may not be as good as
between the 115 and 25V windings.

to make an isolating transformer hook the 25 windings of wto of your several
transformers together (in parallel) and feed 115V in one end and you'll get
most of it out the other end.

Until you load one transformer only whereupon there will be a burning smell.

Graham

 

[Pooh Bear]

I have several toroidial transformers that have two 115v windings and
two 25v windings on each. The way I understand electricity each 115v
winding would only go 1/2 way around the toroid then the 25v winding is
on top of that winding is this correct? or do both windings go all the
way around? that would be more of a 1:1 isolation transformer (if the
25v windings were gone) Am I thinking correctly? Thanks Res.

Best coupling is acheived with all windings going 'all the way round'.

Don't use 2 primary windings for isolation. The insulation used isn't intended
for safety isolation.

Graham

 

[Phil Allison]

"Pooh Bear"

You can't legally use it that way for isolation since the insulation
doesn't
meet safety regs.

** Drivel.

The plastic ( ie polyester tape ) wrap insulation used on typical toroidal
transformers is merely functional insulation. It can and will fail if the
transformer is ever subjected to a serious overload - in some cases,
especially with low VA units, this takes only a few seconds.

A "safety isolation " transformer is one with a secondary voltage less than
50 volts and which is built to remain safe with respect to human contact
with the secondary EVEN if the unit is severely overloaded. The vast
majority of *toroidal* transformers cannot and do NOT meet the "fail safe"
requirements for "safety isolation" use.

Obviously, a 115 volt secondary winding is * UNSAFE * for human contact at
ANY time.





......... Phil

 

[John Larkin]

You can't legally use it that way for isolation since the insulation doesn't
meet safety regs.

Will the Insulation Police bust me? Will they, er, put me into
isolation?

John

 

[Pooh Bear]

Will the Insulation Police bust me? Will they, er, put me into
isolation?

Given today's liability issues, I wouldn't even suggest this in a casual
newsgroup discussion. Note the use of your company in your email addy. Liability
lawyers will note that too and possibly claim it was professional advice.

Graham

 

[John Larkin]

Given today's liability issues, I wouldn't even suggest this in a casual
newsgroup discussion. Note the use of your company in your email addy. Liability
lawyers will note that too and possibly claim it was professional advice.

I'm shocked, shocked that you suggest such a thing.

John

 

[Michael A. Terrell]

I'm shocked, shocked that you suggest such a thing.

John

I didn't think that you had the capcity to be shocked. ;-)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[emmett]

i'll give a shot thanks much for the input, and no I'm not moronic
enough to hold anybody responsible except myself! Good info! Emmett

 

[John Larkin]

I didn't think that you had the capcity to be shocked. ;-)

How did you induce that?

John

 

[Michael A. Terrell]

How did you induce that?

John

With my magnetic personality! ;-)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[John Larkin]

With my magnetic personality! ;-)

I can easily resist that.

John

 

[Rich Grise]

I can easily resist that.

John

Haven't got that capacity to admit it, eh?

;-)

 

[Tim Williams]

Haven't got that capacity to admit it, eh?

He's reluctant to.

Tim