10th January 2007, 09:55 #1
Advanced Member level 5
What is the main difference between a multi strand wire and a single strand wire?
what is the main difference between a multi strand wire and a single strand wire... wat r their advantages and where r they used...
10th January 2007, 09:55
10th January 2007, 14:19 #2
Full Member level 4
Stranded wire (opposite to Solid wire) is composed of a bundle of small-gauge wires wrapped in a particular pattern inside insulation to make a larger conductor. Stranded wire is more flexible than a solid strand of the same overall gauge. Stranded conductors are commonly used for electrical applications carrying signals, a computer "mouse" and for power cables between an utilization device and its power source; e.g.: sweepers, table lamps, powered hand tools, welding electrode cables, mining machine trailing machine cables. Most house wiring to wall switches and receptacles is done with solid, single strand, wire because it is cheaper to manufacture than stranded wire and there is not a need for flexibiltiy in the wire itself as it remains stationary.
The use of stranded conductors adds significant wire surface area. The wire from the electrical service to earth is solid and provides strength and protection against the environment.
High frequency electricity travels near the outside of the wire. This is commondly known as the skin effect and is resposible for some power loss within the circuit. Stranded wire reduces this effect and is therefore ideal for use in coils used as inductors in high-frequency tuned circuits...........
10th January 2007, 15:37 #3
Advanced Member level 4
Another configuration of stranded wire is "Litz" wire. Litz wire consists of many strands of small diameter insulated wire. The idea is to limit the effective diameter of each strand to the depth of the skin effect at a given frequency. By insulating each strand the current is forced to remain within each strand of wire. This has the effect of reducing the resistance at high frequencies.
Litz wire is also used for another purpose. If a transformer has an air gap, the portion of the winding that is adjacent to the air gap will be exposed to "fringing" flux, which induces eddy currents in the winding wire. By using litz wire, the eddy currents losses are reduced in the same manner as they are reduced in a transformer core by the use of insulated core laminations. See the following for more info:
10th January 2007, 15:37
15th January 2007, 12:21 #4
Advanced Member level 5
can u explain how multistrand wire reduces loss due to skin effect...
15th January 2007, 13:35 #5
Full Member level 3
The principle of litze wire is that there are a large number of insulated strands,
inductors if you like, which are all paralleled what results in a resultant inductor with a lower induction. Perhaps that's easier to understand. Each inductor has an inductance which is higher than the inductance of the "big" inductor, but there are a large number of these, all connected in parallel.
The surface area of all the strands added will be much larger than the surface area of one "big" strand. If you want to know what it looks like, find a ferrite antenna of an old (tube) radio. You will see that the litze wire is thicker than the normal enamelled wire and it is wrapped in cloth, no further insulation is needed because the strands are individually insulated.
The same principle is used on printed circuit board tracks where the designer
prefers to parallel four or five narrow tracks which will come together at the ends.
Even lumped capacitors for the GHz range use the same principle, they consist of a square which is soldered directly to the pcb. The other terminal is on top and is connected to the track via a large number of very thin paralleled wires on one edge of the capacitor.
If you want a more technical explanation for the skin effect follow the link:
15th January 2007, 13:47 #6
Member level 5
On high frequencies current flows only in thin surface layer of thick wire, so deeper layers are useless. Many thin wires can carry high frequency currents more efficiently than one thick.
15th January 2007, 15:46 #7
Advanced Member level 4
This is a grossly oversimplified explanation, since it assumes that there is a sudden discontinuity between the portion of a conductor that suffers skin effect and the portion that does not:
Suppose we have a 1cm diameter (0.5cm radius) wire. Due to skin effect, conduction only takes place in the part of the wire from 0.4 cm out to the periphery. The effective cross sectional area that conducts current is pi(.5^2) - pi(.4^2). = .25pi - .16pi = .09pi. Now suppose we use a wire whose radius is equal to the skin depth (.1cm). The entire cross sectional area of this smaller wire conducts current. The cross sectional area of this wire is pi(.1^2pi) = .01pi. It takes 9 of the smaller wires to produce the same cross sectional area as the effective cross sectional area of the larger conductor. We can fit much more than 9 of the smalller wires inside the actual cross sectional area of the larger conductor. Therefore the effective cross sectional area of the stranded wire consisting of as many small wires as will fit inside the cross sectional area of the larger conductor will have a much lower effective high frequency resistance than the single large diameter wire.
16th January 2007, 16:21 #8
Full Member level 5
that was a brilliant explanation... thank you.. i benefited from it..
Originally Posted by Kral