Used in high frequency current carrying applications, Litz wires are constructed with small diameter (0.04mm to 5mm) enameled copper wires, electrically insulated and braided from each other to reduce losses called "skin effect*", generated by opposing electromagnetic currents (Eddie currents). At low frequencies, this phenomenon is considered negligible, although some energy conversion specialists believe that losses are evident from low frequencies.

With simple copper wires, which have low resistance, electric current will tend to flow around the periphery of the conductor. The impedance will then increase, and the percentage loss will increase as the impedance increases, finding that the increase in resistance will grow much faster than the increase in section. The use of multi-stranded wires makes it possible to reduce losses thanks to the reduction of the HF resistance, by skin effect and eddy current. It is thus understood that the use of simple copper wires in modern equipment such as transformers, electromagnets or alternators can lead to catastrophes. The cables are constructed so that "proximity effect" losses are also reduced. We will also choose the type of varnish according to the temperature class (from 150 to 240°C).

Note that the diameter of the unitary wire will be chosen according to the frequency at which it is desired to work, so that their diameter is smaller than the thickness of the skin. See table below.

Mainly used for power conversion, high frequency transmission and reception, power electronics, inductive proximity switches, electronic tags, multiple telephone transmission equipment, coil windings, flexible connections for relays, coils, transformers, motors, etc.

Our manufacturing site based in Spain enables international delivery of our solutions.
We also offer **unitary enamelled copper wires.**

THERMAL CLASS | F155 (155°C) | H180 (180°C) | 200 (200°C) |
---|---|---|---|

Enamel type | Polyurethane | Polyester or Polyurethane | Polyester ou polyamide |

**Cables made of fine enamelled copper wire. Unit threads from 0.05 mm Ø to 5 mm****The choice of the diameter of a single wire is important for the specific application**

Frequency Min (KHz) | Frequency Max (KHz) | Recommended wire diameter (mm) |
---|---|---|

0,06 | 1 | 0,32 |

1 | 10 | 0,25 |

11 | 20 | 0,18 |

21 | 50 | 0,12 |

51 | 100 | 0,1 |

101 | 350 | 0,06 |

351 | 850 | 0,05 |

851 | 1400 | 0,04 |

1401 | 3000 | 0,03 |

**Le câble de Litz est la réunion de plusieurs fils de Litz.Le câblage se fait en couches concentriques, pour réaliser la section nécessaire (7 x 7 x 37).**

**Nous pouvons aussi fabriquer sous forme carrée ou rectangulaire, selon le besoin.Nous pouvons également mettre une couche d’isolation textile.Le câble de Litz se définit par le nombre de fils et le diamètre unitaire des fils :Exemple : 120 X 0,10mm = 120 brins de diamètre 0,10mm.**

** **

**Technical specifications**

**Litz cables can be manufactured in different ways according to the recommendations of the Design Office. TESORAX manufactures them with the wires assembled in the same direction and with a strand pitch less than 60mm. On request, and to meet the needs of our customers, we can form them in rectangular or square section in order to reduce the winding volume. Our Litz cables are manufactured using materials that allow direct welding without the need for a mechanical procedure. Before soldering, the Litz cable must be immersed in a pickling agent and then in a bath of tin (60%) and lead (40%) at a temperature of 375°C to 400°C. The immersion time depends on the number of wires and the diameter of the cable.**

**The losses produced in the coils are due to the factors:**

**Losses in the conductor:****Joule effect****Eddy currents**

**Capacity losses****Losses due to the hysteresis effect of the core**

**The first two factors appear in the coils and the third in those having a ferromagnetic core. We will analyze the first two factors in order to justify the use of the Litz cable.**

**The Joule effect is known that electrical conductors heat up by the passage of current, which has the effect of increasing the ohmic resistance of the conductor and therefore reducing the possible current in the same section. Apparently, it is possible to increase the section in order to decrease the Joule effect, but this would lead to an increase in losses due to eddy currents. Changing the section is therefore not a solution, once it has been defined. We can do as follows: once the section of the conductor has been determined, in order to eliminate the film effect, we can join together, at the calculated section, enamelled cables; in this way we obtain a section which will be maintained during the whole working cycle of the coil. The thinner the threads, the better the result, due to the dandruff effect. However, this solution is expensive. We recommend the ideal calculation of the cross-section which can be studied on a case-by-case basis by a technician.
To calculate the skin current, use the following formula which gives us the current level (depth):Pour calculer le courant pelliculaire, utiliser la formule suivante qui nous donne le niveau (profondeur) de courant:**

**e = Thickness to be calculated //
p = Resistivity of the conductoru = Permeability of the conductive material // f = Current frequency**

**For a copper conductor, the formula takes the following form:**

The value is given in millimeters.

**The resistance of an alternating current conductor is given by:**

** I = Perimeter in mm of the conductor section.For copper, the formula becomes:**

- Studying its dimensions
- Chercher le meilleur enroulement
- Distributing the currents in the coil and Insulating the conductors

- Ohmic resistance
- Total induction
- Total capacity

The end result should be a coil ready for use in the circuit, with the best performance, lowest volume, and best quality while having the lowest resistance loss.

Litz cables are used to:- Reduce losses by Joule effect
- Reduce losses due to eddy currents
- Use smaller magnetic cores
- Obtain capacity in small coils
- Get better quality
- Easy handling of cables for winding, due to wires fixed together
- Extra-flexible cables allowing core winding with a very small bend radius

TESORAX ensures the manufacture according to the DIN 46.447 standard, and studies the cables according to the criteria:

- Number of wires depending on the cable diameter
- The type of insulation
- The support system
- Enamelled copper must be tinned. The outside diameter and other properties of the enamelled copper wire are selected by the manufacturer if the customer does not formally specify them. The outside diameter without insulation is the basis for calculating the outside diameter of the insulated cable: this is not used during reception checks.

- Thickness of each elementary wire
- Total number of wires and bundling
- No stranding
- Insulating

The DIN 46.447 standard defines the types of cables according to each of these 4 criteria. Any question about the effective cross section of the conductor is defined as follows:

- Preset effective section: 0.70mm²
- Individual wire diameter: 0.10mm, i.e. a section of 0.007854 mm²
- Corresponding number of threads: 0.70 / 0.007854 = 89.13 theoretical threads. 90 threads will be used. The studied cable will have the following composition: 90x 0.10mm

**Do not hesitate to contact us for any information: Our design office will be able to guide you in the cable solution that suits you best.**