E55 Ferrite transformer and Litz wire

I ordered the 150 watt solder pot recommended by Michael Terrell:

http://www.ebay.com/itm/391024009808

I also ordered a 1.937 pound bar of 63/37 solder for $17.50:

http://www.ebay.com/itm/182285866372

I'm also thinking about getting some lead-free solder. I can get a bar of 
96.5% tin 3% silver and 0.5% copper for about $20:

http://www.ebay.com/itm/322262071733

There is also a  1 pound spool of silver solder for $18, but I think it is 
more for plumbing and metalwork.

http://www.ebay.com/itm/172324681754

The MSDS shows 90-100% tin, 1-10% copper, and < 1% silver:

http://worthingtonindustries.com/getmedia/4282fa6c-7c96-466a-8ef1-130c491863d1/wc004_premium_silver_lead_free_solder

I should also think about what kind of flux to use for Litz wire and the 
solder pot. Here is standard plumbing flux, but I don't know if it is safe 
for electronic usage:

http://www.homedepot.com/p/Oatey-1-7-oz-Lead-Free-Tinning-Flux-303742/100347302?MERCH=REC-_-PIPHorizontal1_rr-_-100342559-_-100347302-_-N

Here are some solders and fluxes from McMaster:

http://www.mcmaster.com/#silver-solder/=14bthdr (wire 96.5/3/0.5 single flux 
core $104/lb)
http://www.mcmaster.com/#silver-solder/=14btil8 (bar 97% tin/0.2% 
silver/0.8% antimony/2% copper $38/lb)
http://www.mcmaster.com/#7755a1/=14btkq0 (easy clean liquid flux, 16 oz, 
$13)
http://www.mcmaster.com/#7798a12/=14btli0 (fully activated liquid flux, 
$48/gallon)

Here is a page from Superior Flux with their recommended product:

http://www.superiorflux.com/superior_30_supersafe_electronics_soldering_flux.html

This is the easy-clean flux in the list above. I think I will order that.

Thanks,

Paul 

Tauno Voipio wrote...
> On 25.9.16 02:03, P E Schoen wrote:
>
>> I have some 7x3x21 litz wire ...
>
> In the tube era, about half a century ago,
> we handled the litz ends:
>
> 1. Put a wad of cotton into a metal lid,
> 2. Pour some denaturated spirits on it,
> 3. Put the spirits on the wad to fire,
> 4. Heat the Litz end in the fire till the insulation burns,
> 5. Push the hot Litz end with a screwdriver to the wad,
> 6. Pull out sideways and tin the copper ASAP.

 My smallest litz has over 500 strands.  I
 had to learn how to do litz terminations
 after my super-capable prized technician
 died.  He used a small solder pot with a
 tub of ugly brown greaselike flux.  I
 learned from painful experience that the
 flux was a critical part of the process.

 It's not clear to me how flux would fit
 into your six-step scheme.


-- 
 Thanks,
    - Win

On 26.9.16 10:22, Winfield Hill wrote:
> Tauno Voipio wrote...
>> On 25.9.16 02:03, P E Schoen wrote:
>>
>>> I have some 7x3x21 litz wire ...
>>
>> In the tube era, about half a century ago,
>> we handled the litz ends:
>>
>> 1. Put a wad of cotton into a metal lid,
>> 2. Pour some denaturated spirits on it,
>> 3. Put the spirits on the wad to fire,
>> 4. Heat the Litz end in the fire till the insulation burns,
>> 5. Push the hot Litz end with a screwdriver to the wad,
>> 6. Pull out sideways and tin the copper ASAP.
>
>  My smallest litz has over 500 strands.  I
>  had to learn how to do litz terminations
>  after my super-capable prized technician
>  died.  He used a small solder pot with a
>  tub of ugly brown greaselike flux.  I
>  learned from painful experience that the
>  flux was a critical part of the process.
>
>  It's not clear to me how flux would fit
>  into your six-step scheme.
>
>

The trick was to pull the wire out below the flame
through the wet swab, and tin the ends immediately.
The old litzes did not have so many strands, though.

-- 

-TV

PS: Thanks for the great book.

On Monday, September 26, 2016 at 8:41:41 AM UTC-7, Tauno Voipio wrote:
...
> The trick was to pull the wire out below the flame
> through the wet swab, and tin the ends immediately.
> The old litzes did not have so many strands, though.
> 
...

The technique I learnt did not use the swab but just dunked the end of the wire in the methylated sprits so as to cool them rapidly and keep oxygen away from the copper.

The wires would be very clean pink copper - you then flux and solder before they can tarnish.

kevin

"kevin93" <kevin@whitedigs.com> wrote in message 
news:c3a93312-16b8-4035-930e-0a6144d6958a@googlegroups.com...
>
> The technique I learnt did not use the swab but just dunked the end of the 
> wire in the methylated sprits so as to cool them rapidly and keep oxygen 
> away from the copper.
>
> The wires would be very clean pink copper - you then flux and solder 
> before they can tarnish.
>

Oooh-- there's actually a very neat trick going on here.

The spirits /are/ the flux.  Delayed a bit, I suppose.

Hot copper is catalytic around light hydrocarbons.  Demonstration:
https://www.youtube.com/watch?v=jEdK4BQCr_8
Notice the cleaning action: the copper oxide is reduced.  If plunged under 
the liquid surface, the surge of fuel vapor maintains a lack of oxygen, and 
the copper remains clean.

This is the same effect seen under a torch, where the copper surface is 
washed clean or dirty, depending on what part of the flame it's exposed to.

Chemistry is fun!

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

"Winfield Hill"  wrote in message news:ns8u4o0osa@drn.newsguy.com...

>  A solder pot is absolutely necessary, along with a big container of flux 
> to dip the litz into first.  I don't recommend a cheap pot.  You may 
> forget it and leave it on and you DO NOT want any trouble!!  Newark sells 
> the Tenma 21-3511 for $25.  Not too expensive.

I bought a 2 pound chunk of 63/37 eutectic solder, and lopped off a short 
piece using bypass trimming shears:

http://enginuitysystems.com/pix/tools/Solder_Cut_3095.jpg

http://enginuitysystems.com/pix/tools/Solder_Cut_3096.jpg

http://enginuitysystems.com/pix/tools/Solder_Cut_3099.jpg

At that point I just wiggled it until it broke off:
http://enginuitysystems.com/pix/tools/Solder_Cut_3100.jpg

Then I put it in my new $15 solder pot:
http://enginuitysystems.com/pix/tools/Solder_Pot_3101.jpg

After about 5 minutes:
http://enginuitysystems.com/pix/tools/Solder_Pot_3103.jpg

And after 10 minutes or so:
http://enginuitysystems.com/pix/tools/Solder_Pot_3104.jpg

Dipped the #14 Litz wire in #30 flux, and then 10 seconds in the solder pot:
http://enginuitysystems.com/pix/tools/Solder_Litz_3105.jpg

I cut a bit off the end and it looks like close to 100% solder impregnation. 

On Monday, 26 September 2016 01:50:05 UTC+1, P E Schoen  wrote:

> There is also a  1 pound spool of silver solder for $18, but I think it is 
> more for plumbing and metalwork.

much higher temp, no use for components


> I should also think about what kind of flux to use for Litz wire and the 
> solder pot. Here is standard plumbing flux, but I don't know if it is safe 
> for electronic usage:

it's a nono for all electronics as it corrodes the metal over time. It's especially no-go for litz


NT

On 10/04/2016 05:58 PM, tabbypurr@gmail.com wrote:
> On Monday, 26 September 2016 01:50:05 UTC+1, P E Schoen  wrote:
>
>> There is also a  1 pound spool of silver solder for $18, but I think it is
>> more for plumbing and metalwork.
>
> much higher temp, no use for components
>
>
>> I should also think about what kind of flux to use for Litz wire and the
>> solder pot. Here is standard plumbing flux, but I don't know if it is safe
>> for electronic usage:
>
> it's a nono for all electronics as it corrodes the metal over time. It's especially no-go for litz
>
>
> NT
>

There's hard silver solder, which is more like brazing rod, and then 
there's soft silver solder.  Soft silver solder is SnPb with 2% silver, 
which IIRC helps prevent gold intermetallics from forming, so it's good 
for repairing old HP gear with heavy gold plating.  It's also helpful 
soldering small ceramic-packaged photodiodes with evaporated gold pads. 
Those tend to disappear into the solder if you aren't careful.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

On 2016-09-26, P E Schoen <paul@pstech-inc.com> wrote:

> There is also a  1 pound spool of silver solder for $18, but I think it is 
> more for plumbing and metalwork.
>
> http://www.ebay.com/itm/172324681754

says in one of the photos that it melts at 226C so it's at-least compatible with
electroncs soldering practice.

-- 
This email has not been checked by half-arsed antivirus software 

"P E Schoen"  wrote in message news:ns70ni$oh4$1@dont-email.me...

> I am making a transformer with Epcos E55 cores of N27 ferrite. The primary 
> will have four windings each rated for 12-15 VRMS at 50-70 kHz. I am 
> hoping to get up to 1500 watts, so the primary windings will need to 
> handle up to 31 amps. The coilformer (bobbin) has 14 pins, of which 8 will 
> be used for the primaries. The secondary will be two windings capable of 
> 250-300 volts each at the nominal 12/24/48 volts input. For 1500 watts, 
> these will need to be rated at about 3 amps. I have figured on four turns 
> for each primary (about 3.5 volts/turn).

[snip discussion of Litz wire and soldering]

The testing of the transformer made with Litz wire indicates that it might 
be possible to make only about 750-1000 watts, mostly because of the bulk of 
the Litz wire and difficulty getting enough copper to get the required 6 
amps at 250 volts. It was difficult to fit the 50 turns of #20 AWG 
equivalent Litz, and a second coil of the same size would be needed to get 
the power originally desired.

My testing of the small transformers seems to show that the skin effect may 
not be as significant as originally supposed. So I am considering a design 
that uses four copper strips 1/4" wide and 1/32" thick for the primary. Here 
is a rendering of how it might be built, with the primary on the outside of 
the secondary:

http://enginuitysystems.com/pix/electronics/Transformer_E55_NE.jpg

I will probably need to use at least 100 kHz to get 3.75 volts/turn instead 
of 3 V/t as presently constructed with 5 primary turns. However, I just 
realized that this design would be only for 12-15 volts at 30 amps, or 
360-450 watts. I need four sets of four, which will be more challenging. So, 
back to the drawing board.

However, my point was that these 1/32" strips would have 400 uOhms DC 
resistance, and even if AC resistance were 3x that, 30 amps through 1200 
uOhms x 4 turns would be about 4 watts. Four such turns would be 16 watts of 
losses, which is only about 1% of the target 1500 watts. Also, the exposed 
primaries would be conducive to forced air or even convection cooling.

Now to figure how to construct it... ;)

Paul