[SOLVED] Practical advice on terminal connector for litz wire

Hello everyone,

I have Litz wire of 750 strands with 0,2 mm diameter of each wire. Diameter of the total wire (all strands together) counting insulation in is: 7,5 mm (measured). Without insulation (calculated, not measured) it is ~√750 *0,2 = 5,47 mm => it will be a bit more like 27,7x i.e. 27,7*0,2 = 5,54 mm (without insulation).
My litz wire is like in the below picture.


I would appreciate your advice on how to make the terminal connector of the Litz wire. It will be connected to a PCB having a high power circuit (class D power inverter on the full bridge configuration).

I have found some terminals in the following link, but I do no know if those are good for a final PCB connection ? http://www.cardas.com/parts.php

Please recommend me whatever kind of terminal from whatever part of the world (ebay,amazon etc..). It would definitely help me a lot because I have no idea !

Thank you in advance !

Litz wire are used in high frequency application probably above 100KHz, this wires will reduce the skin effect loss due to high frequency
I don’t think you need a litz wire for your application, What is the output frequency of Class D inverter, if it is 50Hz do not use litz wire, Use multi stand insulated copper wire(Current density = 5A/mm^2, ie for 10A we have to use 10/5 = 2mm^2 copper ) , If it is an audio amplifier the frequency will be maximum 20Khz, for audio application use oxygen free copper wire , size according to the current.
Lits wire specification:
https://litzwire.com/nepdfs/Round_Litz_Catalog.pdf
Availability:
https://www.ebay.com/bhp/litz-wire

Rather than 750 strands my experience is with plain automotive battery cable (maybe 100 strands_.

(1) I used a handheld grinding stone on the final 3/8 inch of every wire I could get at, untwisted and straightened. The aim is to remove all tarnish, rather than rely on flux to penetrate it.
(2) Tin every wire with solder.
(3) Pack all wires inside the tube-shaped portion of a copper connector. Remove tarnish on the inside surface beforehand. (As an alternate, squeeze a short length of copper pipe in a vise.)
(4) Heat the connector to melt solder and fill in all gaps. A torch might be needed as well as a soldering gun.

I saw someone recommend this method for hooking up backup power systems.

Depending on the exact nature of the insulation on individual strands, you can burn off the insulation by dipping into a solder pot. Make the temp highest on the solder pot, add some flux (cooking oil may be good enough) and dip the end (say 1/2 inch or 1.5 cm) for sufficient time till be insulation burns off completely and the end is coated well with solder. You will need a suitable lug and a heavy duty crimping tool to finish off the end.

Crimping of soldered litz wire strands doesn't work. It's the same thing as with screw connection of soldered strands. The solder will creep under pressure, leaving an unreliable connection.

The strand can be soldered to the PCB directly, or to a ring or spade cable lug.

I have also seen welded litz wire terminations. But it's rather difficult to make and probably won't work for large strands.

FvM said:

The strand can be soldered to the PCB directly, or to a ring or spade cable lug.

Click to expand...

If I solder to the spade cable lug the soldered litz wire, will it work ? Because I need to get rid of the insulation first exactly as c_mitra said in post #4 (flux + solder pot).

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I mean the tinned wire soldered to the spade cable lug, right ?

Standard litz wire is made of "solderable" enameled wire, the insulation melts when applying solder with sufficient high temperature, as suggested in post #4. There are however "high temperature" litz wire qualities (dark brown enameled wire) which can't be soldered without pre-treatment.

7.5 mm dia litz (effective metal dia about 5 mm) can be soldered to PCB but you will need to worry whether it will serve the purpose. Most likely the PCB copper will exceed the rated values- please check.