Litz wire Inductor

[Njguy]

When constructing an inductor wouldn't using litz wire be better? I don't mean beacuse of the standard function of litz wire in increasing efficiency from skin effect. Wouldn't it be better to use it because you can reduce the number of winds that you have to physically wind due to the multiple strands per wire? Also this will reduce the resistence of the inductor which will allow you to drastically reduce the voltage which will greatly reduce the wattage of the inductor since electromagnetic strength is entierly dependent on amps/loops..? Just curious. Thanks again.

 

[kubeek]

Multiple strands have no effect on inductance and resistnace. The wires are soldered together at the ends so the amp/turns remain the same, and the sum of crossections of the wire is the same as a full wire would need so no difference in resistance either.

 

[Njguy]

Nvm, thanks.

 

[KeepItSimpleStupid]

You can Bi-filar or trifilar or n-filar wind the things if you want to cut down the number of passes you have to make through a torroid. I just wound a bi-filar torroid inductor a few weeks ago.

 

[Njguy]

This is interesting but how do you get the current to flow in the same direction so that it amplifies the magnetic field instead of cancelling it out?

 

[KeepItSimpleStupid]

You just connect the right ends. In my case, I am making a saturable reactor, so I need two separate windings, but if you need lot of turns, you can use two pieces of wire and wind them together and externally connect the phases properly. They should end up near each other anyway.

When you had wind a torroid, you "SPLIT" the wire length half way. i.e. You place the torroid at the half-way point on the wire. Wire 1/2 using one end and the other half using the other, so you don;t have as long of a length to contend with.

 

[MrAl]

Hello there,

Litz wire does not reduce skin effect. Skin effect is a consequence of nature and we cant easily change that. What Litz wire does reduce is the copper lost because of the skin effect. We could in fact find a large diameter wire that conducts the same as several smaller diameter wires, but the difference would be almost all the smaller diameter wires copper would be actually still conducting while most of the larger diameter wire copper would not be.
With one large diameter wire the skin effect might cause very little current flow in 90 percent of the inner cross section, meaning we just lost a wire of equal length but of smaller gauge (the inside non conductor part). That's a whole equivalent wire lost. But break that up into two smaller gauge wires and we see more of the copper in those two wires actually being used. So we end up with a smaller copper loss. If we break it up into even smaller pieces, we may see only 10 percent lost which is a much better figure. This kind of quality measurement would be known as the DC to AC resistance ratio.

Another way to think of it is if we had a large diameter copper wire and much of the inside part of the cross section was not conducting much, if we separated the inside part from the outside layer with an insulation layer, the inside wire would conduct more too and we'd still be using the same amount of copper. So Litz wire improves the AC current to copper ratio, which improves the AC conduction with no additional copper. Of course there is the complexity of producing the wire which would make it more expensive.

If you needed to wind a multiple turn inductor and you used Litz wire to avoid having to wire every single turn, you may find that the inductance isnt quite what you expect. That might be because Litz wire is wound in a very particular manner where the wires are twisted or arranged to equalize certain characteristics of the wire and that may cause less inductive interaction between turns. Normally an inductor is wound one turn after the other where each turn is next to the one right after it, the turns are not arranged in groups of several wound turns which lowers inductance, and the idea of an inductor is to get as much inductance in as small a space as possible. It might work, but not as good as a single turn coil, however it may reduce the side effect of capacitance which affects self resonance.

 

[dr pepper]

Good explantion,

What Mr Als saying is that at high frequencies copper tends to electrically act like a tube, where current travels down the wall of the tube.
Using litz wire is a more efficient way to wind a high freq trans, the equivalent resistance (amongst other parasitics) of litz wire at high freq's would be less than that of a solid round copper conductor.
You could use mutiple smaller round copper wires, I do this it works and is cheaper and for me more easily obtainable.