[Eeyore]

Arny Krueger wrote:

"Eeyore" wrote
Arny Krueger wrote:

Theoretically, cables made up of fine wires or small individually
insulated wires does not address skin effect. Lab measurements bear that
out. Therefore Litz wire doesn't do a lot for skin effect.

Well..... it has to or high frequency smps transformers would be hoplessly
inefficient.

The smps transformers I've taken apart were made with plain enameled wire.
Sometimes a couple of strands for one winding, but I think that was for a
bifilar winding. Heck many SMPS only run at 30-60 KHz - I used to see their
(small) effects when I recorded at 24/96.

Very few smps designs run below 100kHz now. The first one I did was 130kHz. At
such frequencies you don't want any conductor 0.3mm dia.

I took apart a low-voltage 12V DC halogen lighting 'transformer' recently. The
smsps secondary was about 10 strands of ~ 0.3 dia.

200-300 kHz is quite common now, 500kHz not unusual. The parts are available
including the low-loss ferrites for up to 1MHz. Printed windings ( Cu foil 35-70
um ) are sometimes used with these.

Graham

[Arny Krueger]

"Eeyore" wrote in
message ...


Arny Krueger wrote:

"Eeyore" wrote
Arny Krueger wrote:

Theoretically, cables made up of fine wires or small individually
insulated wires does not address skin effect. Lab measurements bear
that
out. Therefore Litz wire doesn't do a lot for skin effect.

Well..... it has to or high frequency smps transformers would be
hoplessly
inefficient.

The smps transformers I've taken apart were made with plain enameled
wire.
Sometimes a couple of strands for one winding, but I think that was for a
bifilar winding. Heck many SMPS only run at 30-60 KHz - I used to see
their
(small) effects when I recorded at 24/96.

Very few smps designs run below 100kHz now. The first one I did was
130kHz. At
such frequencies you don't want any conductor 0.3mm dia.

I took apart a low-voltage 12V DC halogen lighting 'transformer' recently.
The
smsps secondary was about 10 strands of ~ 0.3 dia.

How were the 10 strands wound?

Twisted together?

Next to each other?

My point is that twisting doesn't do much for skin effect because skin
effect is about magnetic fields. Magnetic fields are about geometry.
Sticking in very thin layers of insulation doesn't affect magnetic fields
that much. Thick layers of insulation could make a dramatic enough change.

Twisting insulated wires does not do much to change the geometry of the
composite conductor much unless the conductor is thin and the insulation is
relatively thick. Modern enameled 28 gauge wire (ca. 0.3 mm) seems to miss
the mark. Monster was using more like 24 gauge enameled wire, and it
definitely missed the mark.

Laying small wires out next to each other in a transformer winding will help
skin effect because it dramatically changes the geometry of the composite
conductor.