# Wire size !

#### spike1947

Joined Feb 4, 2016
383
Hi
I am going to rewind a small transformer, the size of the wire it had on was 0.06mm x 9 strands in a bunch, I can't find that size anywere and if I did I would need 9 bobins of that size, I would like to know what single strand size wire I could use that would carry the same current !.

Cheers
Spike

Joined Jul 18, 2013
24,218
Normally 50hz/60hz power transformers are wound with single core conductors.

#### spike1947

Joined Feb 4, 2016
383
Yes, but this one had multi strands joined, I just need the mathamatics here, as to what size in mm2 or Ǿ for a single core wire.
my brain is not working of late .

cheers
Spike

Joined Jul 18, 2013
24,218
Add the CSA of all the single strands to arrive at the one single strand.

#### spike1947

Joined Feb 4, 2016
383
Add the CSA of all the single strands to arrive at the one single strand.
I don't think that is the way, if I did that with. 2.5mm2 and times that by 4 I would get 10mm2, but I don't think the loading of 4x2.5mm2 = 1x 10mm2 !.
Spike

#### Ian0

Joined Aug 7, 2020
4,119
I don't think that is the way, if I did that with. 2.5mm2 and times that by 4 I would get 10mm2, but I don't think the loading of 4x2.5mm2 = 1x 10mm2 !.
Spike
Actually it is. (It's different for high frequency transformers >100kHz)
Think about stranded mains flex vs. solid conductor wires that you wire your house with
1.5mm^2 mains flex will carry the same current as 1.5mm^2 twin-and-earth.
1.5mm^2 mains flex is generally stranded at 30x0.25mm
$$30 \times \pi (\frac { 0.25\cdot 10^{-3}}{2})^2 = 1.473mm^2$$

#### Tonyr1084

Joined Sep 24, 2015
6,611
Not the greatest at math but I think I came up with something much smaller than what you all are saying.

Here's my path:
0.06 dia ÷ 2 = 0.03 radius
Pi R^2
0.03 x 0.03 =0 .0009
0.0009 x 3.14 (pi) = 0.002826 area
0.002826 x 9 (strands) = 0.025434

Now, I know even less about high frequency transformers.

#### Ian0

Joined Aug 7, 2020
4,119
9 strands of 0.06mm is the same as one strand of 0.18mm (0.06*√9)
You can get 0.056mm, 0.06mm and 0.063mm. Don't forget that if you are measuring it with a micrometer you are measuring the diameter including the enamel, and it is sold as the thickness of copper before it is enamelled.
https://www.wires.co.uk/acatalog/SX_0032_0090.html

#### Ian0

Joined Aug 7, 2020
4,119
Just a thought - are you sure that it is 9 strands throughout the winding, or just from the bobbin to the terminals?
Transformers with very fine wire have the wire "skeined" between the end of the winding and the terminal.

#### spike1947

Joined Feb 4, 2016
383
Just a thought - are you sure that it is 9 strands throughout the winding, or just from the bobbin to the terminals?
Transformers with very fine wire have the wire "skeined" between the end of the winding and the terminal.
Yes def 9 strands, and yes they are all soldered together at each end at the last 10mm where they terminate at the spade terminal .
ps: Not possible to scrape off the enamel/laquer too fine just breaks when trying.

cheers
Spike

#### ElectricSpidey

Joined Dec 2, 2017
2,024
I've always used a match and very fine steel wool to remove the insulation on magnet wire.

#### MrSalts

Joined Apr 2, 2020
843
Some modern magnet wire uses a coating that vaporizes at soldering temp. Just solder and check conductivity.

#### DickCappels

Joined Aug 21, 2008
8,159
Belden Beldsol. I have a few spools of it left over from some 1981 - 1982 projects.

#### MisterBill2

Joined Jan 23, 2018
10,533
This postseems a lot like meowsoft's transformer and if the wires are soldered together for the whole length and not insulated then it will result in short circuited tuens and the transformer will fail rather quickly when power is applied. The reason for using multiple strands in a mains power transformer is to make the wire easier to wind..

#### spike1947

Joined Feb 4, 2016
383
This postseems a lot like meowsoft's transformer and if the wires are soldered together for the whole length and not insulated then it will result in short circuited tuens and the transformer will fail rather quickly when power is applied. The reason for using multiple strands in a mains power transformer is to make the wire easier to wind..
Hi

#### spike1947

Joined Feb 4, 2016
383
Belden Beldsol. I have a few spools of it left over from some 1981 - 1982 projects.
Hi
Would you be interested to sell one ?,<Mod: deleted email address, prevent spamming.E>
cheers
Spike

Spike use a Conversation chat.

#### MisterBill2

Joined Jan 23, 2018
10,533
Hi
Wire with insulated strands is called "Litz wire" and is useful for higher frequency applications. It offers NO ELECTRICAL BENEFIT AT ALL at mains frequencies. it would be easier to wind than an equivalent solid wire but that makes no sense for this application.
When the transformer unwinding process is completed perhaps the reason for using that type of wire will become clear. If that wire is indeed used t connect to the 400volt low current winding then it is probably used as a short extension of the much finer wire used for the many low-current turns required. Rather unusual to see it done that way.

#### spike1947

Joined Feb 4, 2016
383
Wire with insulated strands is called "Litz wire" and is useful for higher frequency applications. It offers NO ELECTRICAL BENEFIT AT ALL at mains frequencies. it would be easier to wind than an equivalent solid wire but that makes no sense for this application.
When the transformer unwinding process is completed perhaps the reason for using that type of wire will become clear. If that wire is indeed used t connect to the 400volt low current winding then it is probably used as a short extension of the much finer wire used for the many low-current turns required. Rather unusual to see it done that way.
Hi
Thanks for your reply, I have all ready unwound the 400v winding, I had to do that first to get at the primary winding were the fault lies, have new primary wire but not the 400v secondary wire .

Note: The 400v secondary winding is laid on top of the primary winding !.
cheers
Spike

Joined Jul 18, 2013
24,218
Note: The 400v secondary winding is laid on top of the primary winding !.
cheers
Spike
Typically the primary IS always wound on first.