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Litz Wire: Round, Rectangular, Formed and Compacted Profiles

Litz Wire consists of a number of individually insulated magnet wires twisted or braided into a uniform pattern with the primary benefit of reducing A.C. Losses in high frequency windings.  Originally, “Litz Wire” by definition derived from the German word “Litzendraht”, describing a conductor consisting of a number of separately insulated strands that are twisted or braided together.  Each individual wire inherently captures all available positions within the cross-section equally across the whole conductor, capturing full fill factor.  Typically, there is very little voltage losses from strand to strand as there is a temperature rating associated with the film insulation and this provides a dielectric break between the strands.

Litz Wire is seen in High Frequency, High Power Inductor Applications often used in power conversion, Induction Coils for wireless power transfer and Motors and Generators as Litz Wire helps minimise losses in the very high field strengths.
 
The Theory of Litz Wire in 2017: Size and Power Verses Losses:
Basic Theory behind Litz Wire includes magnetic and electrical theories whereby a magnetic field is created by the current or the current can in turn be created by the magnetic field, naturally seen in Motors, Transformers and Electromagnetic Device Applications.

In recent years, there is a trend to reduce both size and weight in most applications whilst keeping subcomponents as affordable as possible. Consequently, frequencies are rising as designers choose to take advantage of higher coercive forces and denser fields, resulting in a requirement for Litz Wire Technology emerging strongly. However, as frequencies increase, so do losses and you create higher coupling and stronger fields resulting in a loss in the materials due to two effects – Skin Effect and Proximity Effect.

By definition, Skin Effect Loss is caused by the current concentrating toward the outer surface of a wire as frequency is increased and Proximity Effect Loss is caused by interaction between magnetic fields of adjacent conductors which affects the distribution of the current.

As the frequency rises, the current migrates to the skin and the current is pushed away by the field of its neighbouring strand making the core of the conductor useless. The center core becomes wasted space, causing the application to be heavier. This is where Litz Wire shines, as Litz Wire mitigates both the Skin Effect and Proximity Effect Losses leading to an AC Resistance that approaches the same resistance as at DC, resulting in significant power savings without an increase in copper mass.
 
Litz Wire: How to Eliminate Skin Effect and Proximity Effect:
As we can calculate skin depth, we can design with strands that are smaller than the skin depth and transpose those strands throughout the length of the wire, twisting to ensure all strands reach the surface of the bundle.  Each strand is then subjected to the same magnetic field so the Inductance is equal on all strands. Each strand will have a marginal layer of film to ensure the current does not flow solely on the overall bundle surface. The ideal strand size is based upon the frequency of the application as seen in the table below:

 
Frequency Recommended Wire Gauge Nominal Diameter over Copper DC Resistance
Ohms/M max
Single Strand
RAC / RDC
60 HZ to 1 KHZ 28 AWG 0.0126 66.37 1.0000
1 KHZ to 10 KHZ 30 AWG 0.0100 105.82 1.0000
10 KHZ to 20KHZ 33 AWG 0.0071 211.70 1.0000
20 KHZ to 50 KHZ 36 AWG 0.0050 431.90 1.0000
50 KHZ to 100 KHZ 38 AWG 0.0040 681.90 1.0000
100 KHZ to 200 KHZ 40 AWG 0.0031 1152.30 1.0000
200 KHZ to 350 KHZ 42 AWG 0.0025 1801.0 1.0000
350 KHZ to 850 KHZ 44 AWG 0.0020 2873.0 1.0003
850 KHZ to 1.4 MHZ 46 AWG 0.0016 4544.0 1.0003
1.4 MHZ to 2.8 MHZ 48 AWG 0.0012 7285.0 1.0003
 
Therefore, it is essential in any given Litz Wire Enquiry to understand what the operating frequency is, so that the correct gauge size of the magnet wire can be utilised in the design. The result is a smaller Litz Wire cable carrying a higher current where the Litz will effectively utilise the whole cross-section of the conductor at frequency. This only applies to Litz Wire as each individual strand is insulated separately. Litz Wire reduces the magnetic field and cross-interference as every strand in the Litz Wire is taking up all possible positions equally, so that the magnetic field cannot build but is instead dissipated.
 
Litz Wire: The Benefits:
Litz Wire offers substantial benefits when incorporated into your Product Design. These include:
  • Reduce A.C Losses in High Frequency Windings
  • Increased Efficiency
  • Mitigation of both Skin Effect and Proximity Effect
  • Minimum Eddy Current Losses
  • Lowered Operating Temperatures
  • Reduced Footprint of Final Product
  • Substantial Weight Reduction
  • Avoidance of “Hot Spots”.
 
Litz Wire: A Manufacturer with History:
OSCO, partnered together with New England Wire Technologies, the original Litz Wire Manufacturer in the United States on a commercial basis since 1898, design, develop and manufacture Litz Wire designs to individual customer specifications. Through our exclusive partnership, we can provide unlimited options for your Litz Wire including type and construction, temperature ratings, enamel thickness, mechanical protection layers, thermal protection layers and cross-sections.
 
Litz Wire: Types and Constructions for all Applications:
With eight Litz Wire Types, ranging from Round (Type One to Six) to Rectangular (Type Seven and Eight) in Profile, there is a Litz Wire for all applications. 

Type One Litz construction includes a single twisting operation with optional outer insulation.
Type Two Litz features bundles of twisted wire, twisted together with optional outer insulation.
Type Three Litz presents insulated bundles of twisted wire, twisted together with optional outer insulation.
Type Four Litz Profiles contain bundles of twisted wire, twisted around a central fiber core.
Type Five Litz features insulated bundles of Type Two Litz Wire, twisted around a fiber core.
Type Six Litz comprises insulated bundles of Type Four Litz Wire, twisted around a fiber core.
Type Seven Litz includes insulated wire, braided and formed into a rectangular profile.
Type Eight Litz construction features single insulated strands twisted and compressed into a rectangular profile.

In addition, Custom Shaped Profiles can be manufactured including Square, Keystone and Cooled Litz Wire Profiles.

Square Profiled Litz Wire allows for the best possible use of the available winding space in your application.
Keystone Shaped Litz Wire provides the best wire packing density allowing for the winding of perfect segments.
Cooled Litz Wire Profiles use a tube core to carry coolant through the Litz, increasing the current carrying capacity of the winding as there is no longer a dependency on the cable being air cooled.

For more information on our Litz Wire Types and Constructions, please visit http://www.osco.uk.com/products/cable-and-litz-wire/litz-wire-winding-wire.
 
Litz Wire: High Copper Fill:
Typically Type Seven and Eight Rectangular Compacted Litz Wire Profiles, alongside Square and Keystone Shaped Profiles are used in Winding Applications to utilise all the available space in the winding slot. These profiles can be readily designed and manufactured and offer an aspect that will help achieve your target field generation.

Advances in forming and compaction of wire has allowed for much higher fill factors than the 40% area loss seen in some published articles. Through design expertise and precise manufacturing, we have seen up to 85% copper fill and as low as 15% area loss.

In many high-energy cost applications, it is most important to maximise efficiency to reduce overall operating cost however, in some applications with lower operating cost, component cost is more critical than overall efficiency. There is a misconception that Litz Wire is deemed to be very costly however even our Formed and Compacted constructions with excellent fill factor and copper density can be designed with cost verses performance in mind. In either case, Litz Wire can help increase efficiency and reduce copper mass in your application.
 
OSCO: Making a significant difference to competitive advantage:
OSCO thrive on Custom Litz Wire projects, developing a Litz Wire design that is both innovative and challenging. Whether you are considering increasing Efficiency, increasing the output of your application or reducing the size of the device, OSCO can help you utilise Litz Wire and see the benefits. Below are a handful of testimonials from our customers that highlight complete customer satisfaction:

“When working with OSCO on Litz Wire requirements we have always found them to be very knowledgeable with an understanding of the types of applications the wire is to be used for. We have no hesitation in working with OSCO when it comes to sourcing wire as they are a pleasure to do business with.” – Manufacturer of Motor Drives.

“We have been trading with OSCO now for a number of years buying quality wire to suit our manufacturing process.” – Manufacturer of Transformers and Inductors.

“OSCO are considered a very valuable partner and their support through both the development phase and through production has made a significant difference in our competitive advantage. Their support always exceeds expectations and in effect they are an extension of our organisation. Any organisation that has very demanding requirements such as ours should consider using OSCO.” – Motorsport Manufacturer.
 
Contact our Sales Team today on 01908 376688 to start your Litz Wire Project with OSCO today and review our Litz Wire designs currently in stock at http://www.osco.uk.com/shop/litz-wire.  
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