Re: The Decision- Solid or Stranded Wire?
- I appreciate everyone's advice. I'm sure my project in being done the right way.
--- In Electronics_101@yahoogroups.com, Stefan Trethan <stefan_trethan@...> wrote:
> That's not stranded, that's litz wire for RF.
> The individual strands of litz wire are insulated with laquer.
> Regular stranded wire with bare strands has no HF advantage.
> I cringe when I read about using stranded wire for screw terminals.
> You should only use stranded wire in screw clamps if the terminal is
> approved for that (usually cage clamps only).
> Otherwise you really need to install a ferrule on the wire first.
> Solid wire is approved in most clamps, as long as the correct
> tightening torque is observed it will not be damaged excessively.
> The reason to use solid wire is mostly because it is cheaper, or at
> least used to be.
> There are some applications where the rigidity helps keep things tidy,
> like wiring switchgear, but nowadays stranded wire is almost always
> used for that because it is faster to install, even with the
> additional work of installing ferrules. Nobody has time for neatly
> bending and routing solid wire any more. I was still trained in school
> to bend correct eyelets on wire ends, haven't seen a terminal that
> required eyelets in some time....... At least I didn't learn lacing
> any more, that'd make me really old....
> On Sun, Jun 16, 2013 at 7:07 PM, Leon Robinson
> <leon-robinson@...> wrote:
> > Charles,
> > Stranded is better for RF applications, Greater surface area equals lower
> > RF resistance (skin effect), as well as more flexible.
> > Leon Robinson K5JLR
- Clamps approved for stranded wire generally enclose the wire on all
sides, so that no strands may escape.
They also don't press into the end of the wire with the end of a
screw, which easily cuts strands.
The goal is to avoid carrying the current with just a few strands, and
making a strong mechanical connection.
Remember that this isn't about what you or I can do with a single
connection but about what is approved by the manufacturer and will
work reliably each and every time.
As for solder tinned ends, EVERY SINGLE connection I have found solder
tinned and clamped, that was left for some years was loose, many to
the point of causing failure or local overheating of the terminal.
There is a simple experiment you can do to prove this point:
Take a length of solder wire, wind it around your finger into a spiral
or coil. Hang it up by one end.
If you want, take a length of similar diameter copper wire and do the same.
After a short while (depending on wire diameter minutes to hours) you
will find the solder coil has straightened out, just from the pull of
gravity. Solder cold flows much more and under much lower pressure
On Wed, Jun 26, 2013 at 11:58 PM, epa_iii <palciatore@...> wrote:
> I spent over 45 years designing, installing, modifying, troubleshooting, and everything else to do with electronic installations. In that time I have installed many thousands of wires in terminal blocks of various different designs. I have never heard, never been taught, never saw any written prohibition, or seen, heard, or came into contact with even any slight suggestion that tinning wires prior to installation in a terminal block was the slightest bit undesirable. I guess I must have missed something.
> Most of the problems that I did see with wires terminated in terminal blocks were due to one of the following reasons:
> Nicked solid wires or broken/missing strands due to improper technique when stripping them,
> Strands that found their way from one terminal to an adjacent one, causing a short or smoke,
> The use of improperly crimped spade or ring lugs or ferrules,
> Wires that were stripped either too long or too short.
> Frankly, I never saw even a single instance of a tinned wire causing any kind of problem. Copper flows almost as much as solder and these types of connections should be re-tightened periodically, especially if there is vibration present.
> Perhaps this is an electric thing as opposed to an electronic one. I can see where a tinned wire may be a problem in a high current connection where heat may be generated and the solder may melt.
> Can anybody explain to me precisely what the mechanical details are that make a screw type connection (of any sort) not suitable for one type of wire or the other? I mean, either the wire is clamped under the head of the screw or there is some kind of intermediate piece that the screw bears on and that, in turn, bears on the wire. In both cases, if the screw is properly tightened, the copper wire is compressed and deformed to some extent, increasing the area of contact and lowering the resistance. This also helps to make the connection gas tight so the areas in contact do not corrode over time. Now, precisely what details of this construction favor one type of wire over another? I would like to know.
> Otherwise, I tend to put all the prohibitions mentioned in the category of old wives tales.
> I said it before and I will say it again,
> Movement and/or vibration = stranded wire. No movement or vibration = solid wire. And that is IT.
> Paul A.
> --- In Electronics_101@yahoogroups.com, Stefan Trethan <stefan_trethan@...> wrote:
>> I find it interesting that you tell us how silly it is to discuss this
>> at length and then go on to suggest the only practice absolutely not
>> allowed in any installation. Tinning wires - no matter how far back -
>> and installing them in a terminal.
>> On Fri, Jun 21, 2013 at 12:29 AM, epa_iii <palciatore@...> wrote:
>> >. My solution was to tin the ends of the stranded wires while leaving part of the stripped length UNTINNED to trap all strands while > ensuring flexibility at the connection point.
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