Transformer winding wire capacity

[eem2am]

Hello,

The following datasheet for enamelled copper wire (ECW) states that ECW of diameter 0.56mm (SWG24) has a current carrying capacity of 0.381A.

Enammelled copper wire datasheet:
https://www.farnell.com/datasheets/24248.pdf


However, the following web page states that wire of diameter 0.574mm (AWG23) has a transmission current carrying capacity of 0.729A.

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies

So, whn I am winding my SMPS transformer primary winding, in which the RMS current is 0.58A, will I be OK with ECW of diameter 0.574mm?

…according to the second reference, I will be ok, according to the first, I will not be OK………..who should I believe?

 

[dick_freebird]

Bear in mind that wire capacities are often rated at a
particular temp, or in free air, and in the transformer
there is a real thermal path problem for the captive
winding layers. As current goes up, so does self heating
and the current capacity derates. How you'd figure that
accurately, is a challenge.

It's pretty easy to get a 2:1 disagreement just with tens
of degrees of assumed temperature. And if the temp rise
allowed is more about insulation degrading, than copper
fusing, that's a whole 'nother dimension of concern (and
likely a well lower max use temp),

 

[srizbf]

trfr winding current capacity is based on temperature rise permitted.
the two different solutions are due to the diff in temp permitted for their design.

in general if you refer two tables then you get two wire size.

select the more dia wire for high temp.
select the less dia wire for less temp rise .

 

[FvM]

trfr winding current capacity is based on temperature rise permitted

As far you refer to transformer design, the values depend also on the transformer type. Giving a value without this information is useless.

 

[rvionics]

For SMPS - high frequency transformer, general thumb rule is 400 to 500 Cm / Amp of current
but you can really reduce your wire size depending upon the number of turns & the loss /temp rise you can allowed in the wire. There are some very good articles from unitrode (now on TI web site) which
will give you good guide lines .