louvered contact band for every fprm of connector design

louvered contacts for sockets, pins and flat conntors such as busbars

What is Louver_tron contact band and what are the benefits of multiple contact points in a connector?

The basic common principle of all Louver_tron contact strips is to provide multiple contact points in a very dense arrangement of consecutively sprung contact elements that are arranged in parallel.

Louver_tron is a product family within the weftron product range of electrical contact band and electrical contact strip designs.

When inserted between precision machined metal parts they will provide precisely defined spring loaded contact points. For high performance electrical connections a high number of contact points is obviously a key requirement. Furthermore  the physical width, thickness and surface treatment of the required contact bands need to be considered. Therefore weftron contact bands with dense arrangements of contact points are available in several variations. Depending on the application and performance requirements different weftron louvered contacts or contact lamella may be selected.

The basic common principle of all Louver_tron contact strips is to provide multiple contact points in a very dense arrangement of parallel, consecutively arranged sprung contact elements. In absence of a defined technical term, the individual sprung contact elements are commonly compared with similar looking technical elements. Hence also referred to as contact lamella, louvered contacts or crown springs. In the final application these multiple current points have significant advantages over contact systems with less or with only one or two current paths.

Any contact system and hence any connector will cause a certain resistance in an electrical system. In critical and demanding applications it is essential to assure the least restriction to current flow. So the main design inherent advantage of Louver_tron louvered contact band is easily explained with Ohm’s law. In a system of electrical resistors arranged in parallel, the total resistance is a function of:
(average resistance per resistor) / (number of resistors)

So the resistance calculation of a contact system using Louver_tron is:
(average contact resistance of individual louvered contact) / (number of louvered contacts).
Find out how you can easily integrate your own design of a High Power Connector or Low Loss Connector using Louver_tron louvered contact bands and add value to your overall design here…..

Contact Band for DIY High Power connectors

Louver_tron louvered contacts add value to your design by allowing to integrate a High Power - Low Loss Connector right into your product.

Having to resort to off the shelf componets for an otherwise awsome design can be frustrating. The only reason to do so would probably be to avoid tooling costs. So let's see how weftron Louver_tron contact band may help to make your design awsome again.

No connector is the best solution

In an ideal situation and for system performance it is best to avoid electrical connectors wherever possible. Since that is not always possible the next best option would be to bolt two conductors together. However, as easy and safe as this sounds even a bolted electrical connection is not as trivial as it may appear. With several parameters to be observed in different environments and especially at high currents.

What if you need a connector....

The function of electrical connectors is dependent on a multitude of parameters. The simplest form would be to have a hole in one conductor and to push a conducting pin of a matching diameter into this hole. Simple yes but it would not work for very long. Many papers and books have been written about electrical high power connectors. It is not the intention of this writing to go into such scientific details. However, most all separable high power electrical connectors have one thing in common.

Basically a certain level of spring force between the mating components is required. These connecting components can be of circular shape as in a - pin and socket- connector.  Or in a flat shape such as in -fork and blade- type connectors. For example like in busbar type connectors. Louver_tron contact strip is suited for both. The required spring force in connectors depends on their application. There is no good or bad in spring force. High spring forces in electrical connections have advantages and issues just as low spring forces will have. With weftron louvered contacts the spring force may be optimally adopted to the application by choosing optimized dimensional parameters for the mating connector pair.

So lets go back to the example of drilling a hole in a conducting metal component and wanting to connect a mating pin. The number of points where pin and socket connect will not be definable or repeatable. There will be no spring force in such a “connector” which is required to compensate for thermal, mechanical, environmental influences. lt will not work reliably or not at all after a certain time.

=> weftron Contact Band for DIY High Power Connector / Low Loss Connector.

weftron Louvered contacts will provide this missing spring element for such a self designed high power connector. And it will provide a maximum of precisely definable contact points between the two conductors. When observing certain design parameters for socket and pin an excellent high current connector with very low contact resistance may be produced from highly conducting metals such as copper, aluminum or brass. The same holds true for producing flat high power connectors such as busbar connectors.

The same high current - low resistance multiple contact spring element may be applied in such a flat connector systems. In fact, connectors using weftron louvered contacts are far superior to most other high power connector systems available in the market. Louvered contact cages are used in highly critical environments. They are used in medical devices, in aerospace, military, in automotive and in - power transmission & distribution - applications. The property of very low contact resistance as mentioned in the previous post on "What is a Louver_tron contact band?" allows for very high electrical power connections. 5000A and more for example in -power transmission and distribution- applications, as well as very low losses in test and measuring equipment or in medical devices.

 

contact band for busbar and for circular connectors

press in louvered contact socket for power take off in busbars

Louver_tron contact band adds value in product design

High Current Connectors are a complex subject and among several interdependent parameters, the number of contact points and reliable contact forces are key elements to electrical connectors.

weftron Louvered contacts enable product designers to add value by making High Current Connectors part of their design.

Electrical connectors are a complex subject. Among several interdependent parameters, the number of contact points and reliable contact forces are key elements to electrical connectors.
With weftron Louver_tron contact band a product designer will be given the missing link. Everything else is standard dimensional specifying of conducting cooper or brass components. All the critical parameters that make a connector function are covered by weftron.com contact band. Of course, weftron will also assist in specifying those mechanical design parameters.

Basic procedure for design integration:

Two machined mating conducting surfaces are machined according to weftron recommendation. Subsequently weftron Louver_tron contact band is inserted inbetween those surfaces. Thereafter the design inherent features of weftron contact band will take over the rest that is needed for a High Performance - High Current Connector. A very dense arrangement of individually sprung contact elements will provide multiple contact points. More current paths per footprint than most other contact systems available on the market. How a multitude of low resistance contact points arranged in parallel benefit the total resistance of a contact system is quickly understood when remembering Ohm’s law. So in fact the key feature of weftron contact band is extremely low connection resistance. A feature that is very key to High Current Connectors.  But also to other applications depending on low electrical losses such as in medical or testing equipment.
As there is a toss of benefits between higher and lower contact forces, the contact force of Louver_tron contact band is easily adjusted. This is done by altering the dimensional contact chamber layout in order to suit the application’s requirement. The rest is up to creativity in product design. So instead of adopting appearance and performance to “off the shelf connectors” Louver_tron contact band enables the economical integration of High Performance Connectors right into the product.

rotating high current contact performing @ 20kA

rotating high current contact performing @ 20kA

High Power Rotary Contact Applications from 100A to 10.000A and Higher
with weftron's Louvered Contact Band

The task at hand for this High Power Rotary Contact was to transfer a current load of >5000A into a bi-directionally rotating copper shaft. Extended field usage have prooven the succesfull accomplishment.Electrical connectors are a complex subject. Adding the requirement of a high power rotary contact feature contributes even more to the complexity of such a desig. Among several interdependent parameters, the number of contact points and reliable contact forces are key elements to electrical connectors.

With weftron Louver_tron contact band a product designer will be given the missing link. Everything else is standard dimensional specifying of conducting cooper or brass components. All the critical parameters that make a connector function are covered by weftron.com contact band. Of course, weftron will also assist in specifying those mechanical design parameters. Two machined mating conducting surfaces are machined according to weftron recommendation. Subsequently weftron Louver_tron contact band is inserted inbetween those surfaces. Thereafter the design inherent features of weftron contact band will take over the rest that is needed for a High Performance - High Current Connector. Or, as in the particular application, a High Power Rotary Contact solution.

Multiple current paths for high performance

A very dense arrangement of individually sprung contact elements will provide multiple contact points. More current paths per footprint than most other contact systems available on the market. How a multitude of low resistance contact points arranged in parallel benefit the total resistance of a contact system is quickly understood when remembering Ohm’s law. So in fact, the key feature of weftron contact band is extremely low connection resistance.

A feature that is very key to High Current Connectors. But also to other applications depending on low electrical losses such as in medical or testing equipment. The special feature of High Power Rotary Contacts for example, are beneficial in the design of machines working on the basis of electrical induction or in robotic applications.As there is a toss of benefits between higher and lower contact forces, the contact force of Louver_tron contact band is easily adjusted. This is done by altering the dimensional contact chamber layout in order to suit the application’s requirement. As for Example in High Power Rotary Contact applications. The rest is up to creativity in product design. So instead of adopting appearance and performance of a product design to “off the shelf connectors” Louver_tron contact band enables the economical integration of High Performance Connectors right into the product.

louvered contact band for every fprm of connector design

 

Louvered Contact Band
- Technology

louvered contact bands are precision stamped metal strips. Specifically used for electrical power and signal transmission between metal components of an electrical connection. Markedly louver shaped contact bridges are arranged in parallel along the length of the stamped metal band. Similarly to ladder rungs they are attached to the side rims of the metal strip.  So these louvers perform as individual mechanical torsion springs when in use between two mating metal surfaces as well as electrically conduction elements.

Mating metal components

The mating metal connector components may be round in shape as for example in pin and socket connectors. Furthermore they may be flat as for example with fork and knife type contacts such as busbar connectors. Or they may also be used in between two flat mating surfaces such as pressure plate connections. So the louvered contact band will be fixed to either of the mating components. Hence it will be compressed to working height when both components are mated. In this mated condition the individual contact bridges will exert even and precisely defined mechanical spring force between the two components and will perform as the functioning conducting elements for passing electrical current.

Each of the contact bridges act as precisely defined contact points that represent low resistance connections arranged in a parallel circuit. In reference to Ohm's law the more contact points per foot print the lower will be the total contact resistance of the connector.

Electrical connectors are often used under extreme mechanical and environmental conditions. With high current loads on small footprint. Subjected to heavy vibrations as well as continuous micromotion. Extreme temperatures and aggressive environments.

Such conditions require high quality electrical connections. Connectors with Louver_tron contact band by weftron.com are the best choice to provide High Performance Contacts for those special requirements. Louvered contact bands may be classified in two categories. - Single component contact bands - which are stamped from one material and - Multi Component contact bands - which are composed of a carrier strip of one material with attached individual contact plates of another material.
Continue reading about the materials used in louvered contacts.....

 

louvered contact band for high power connectors

Louvered Contact Band
- Materials

The predominantly used material for louvered contact band is a special Beryllium Copper Alloy. Especially when speaking about  - Single Component Contact Bands -.  Although pure grade copper would offer much better electrical conduction the mechanical spring properties of hardened CuBe alloy are required for the functionality of a pluggable electrical connection. Albeit the lesser electrical conductivity CuBe is a very good thermal conductor. Beneficial for heat soaking the temperature away to the metal components of the connector that will develop by material inherent electrical resistance at each contact point .

Contact resistance

Further improvement to lower contact resistance may be achieved in selecting suitable surface treatments for the louvered contact band. Any oxide layer on metal surfaces will act as an electrical insulator. Although Louver_tron louvered contact band is designed to break this oxide layer and wipe it away from the contact points during the mating of the connecting parts the oxide layer of bare copper is a quite hard. Increasing the spring force will help in wiping such hard insulating layers. This however comes at the cost of damaging the surface of the mating component after a relatively low number of mating cycles.

For this reason it is recommended to use surface platings on the metal components and on the contact band. For high power low resistance electrical connection silver is the preferred choice. The conductivity of silver is ranking among the highest and the oxide layer of silver is quite soft. Allowing an optimum setting of spring force for high performance and long contact life.

Conductivity

Using pure grade copper for the conducting element between the connector components increases conductivity as compared to beryllium copper. However copper does not provide the necessary spring force that is functionally necessary. The way to solve this is by creating - Multi Component Contact Bands. Such such as weftron.com Louver_tron 112 or Louver_tron 108.
The spring feature in these Multi Component louvered contacts is provided by a separate carrier tape. Either made of stainless steel or of CuBe on which individual copper contact plates are mounted. Here again the surface treatment of choice for the contact plates is silver. The carrier tape does not necessarily require surface treatment. Unless when used in chemically hostile environments and gold will have to be used to protect all surfaces.

From an aspect of production effort and cost - Multi Component Contact Bands - are  much more complicated to produce than contact bands made from a single metal strip. Nevertheless there are applications when such - Multi Component Contact Bands - have no matching alternative. Due to their individual contact plates higher electrical and thermal conductivity and their larger mass they fulfill specifications with high short circuit currents when single component contact bands would fail.

Continue reading about the function of louvered contacts ....

contact band for busbar and for circular connectors

high current contact for for switchgear applications

Louvered Contact Band
- Function

Certain technical design provisions will need to be observed when using louvered contacts.  Similarly as it is the case for any mechanical spring application. So for a spring to function properly it will require a certain deflection. With no deflection there will be no spring force and no defined conduction between the two metal connector components. Over-deflection (over-compression) of the contact band elements however will damage them. Since they will be compressed into a mode of plasticity preventing the spring elements to return to their original uncompressed state.

Grooves for performance tuning

The best suited compression state of the contact elements is achieved by inserting them inside grooves. Such grooves will be machined into one of the mating metal components. The depth of this groove will limit the maximum compression of the contact spring elements. Therfore it will need to be machined with very tight tolerances. Thus achieving dependable repeatability of connector performance. In addition to spring tuning this groove will also hold the contact band in place. Different groove geometries may be chosen for certain applications.

For large socket diameters, for installations on a pin or for installation on a flat connector pair such a geometry may have the form of a dove-tail groove. For other applications it may be sufficient to use rectangular cut grooves. Although it is possible to use contact band without these grooves when taking great care to prevent uneven spring loading and over-compression during mating of the connector components this is not a recommended method for multiple mating cycles or for series applications.

With a contact band inserted and compressed between two electrically conducting components certain power transmission will be achieved.  It is safe to say that this power transmission will always be higher as compared to having a separable pin and socket connector of same size and material without using a spring element between the two. It is also safe to say that when observing best practice this level of power transmission and connector performance will be better than with most other available connector technologies.

Continue reading about the features of louvered contacts ....

louvered contact band for high power contacts

crown spring contact band for high power connectors

Louvered Contact Band
- Features

The final level of achievable power transmission when using crown spring contact band is dependent upon several parameters. Some of which are dependent upon best practice, the choice of material and quality of workmanship. Whereas others are variable by design and adoptable to application requirements.

The most common metals used are copper(1), aluminum(0.75) or brass(0.6). The numbers in brackets indicate a ball park figure for determining conductivity factors. Based on copper having a factor 1. Nevertheless it is possible to use any conductive material for the connector components.  Silver is the most common surface plating for high current applications. Whereas Gold will mainly be used for applications in aggressive environment. Although there are further reasons for gold platings. Such as in applications underlying micromotion between the connector components.

The current loading capability of the crown spring bands themselves is mainly influenced by their physical design. Also by the base material, the material thickness, surface plating and by the number of contact points per defined footprint. For two contact bands with all parameters being the same but with different number of contact points the one with more contact bridges will allow a higher load of power transmission.

This is one reason for Louver_tron 313 crown spring with a contact bridge spacing of 2mm being superior to other known crown spring contacts with a contact bridge spacing of 2.5mm or higher.

Heat dissipation

Contact Bands themselves are much lower in mass than the metal components in a connector. Therfore their thermal capacity is much lower. They depend upon the heat sinking capability of the metal connector components to quickly dissipate heat which will generate under load. This pertains to the choice of the material for the metal connector components as well as the minimum cross section of these components required to handle the load.
Nominal current rating for electrical contacts are usually quoted in conjunction with allowable temperature rise. A connector made of steel components for example and a max. permissible temperature rise of max. 40°C will reach this temperature limit at a lot lower current load than a connector made of copper components.

Continue reading about tuning performance parmeters ....

for ESP (electrical submersible pumps)

louvertact contact band for ESP (electrical submersible pumps)

Louvered Contact Band
- Tuning

Metal components for louvertac type contact band need precsion machining. So in addition to very tight dimensional tolerances a very precise and smooth surface is required. Thus limiting surface roughness. Thereafter completed with a high quality connector grade surface treatment.

Each type of louvertac contact band will have a certain range of working height. This working height is established when installing the louvertac contact inside a machined groove. Thus limiting the deflection of the louvers during mating. Preventing the louvers from being deformed or damaged.
The deflection of the louvers will translate into spring force once mated. So recommended groove layout will be provided for a optimal starting point. The fine-tuning of electrical and mechanical performancehowever will need to be established in application testing.

Contact spring compression

As before mentioned this compression value will be achieved by the depth of the groove in which the band rests. Subsequently it is up to the designer of the contact system to find the most suited compression rate for the actual application in which the contact bands are used. Maximum compression provides best power transmission performance but comes with the cost of high mating forces, increased wear on surfaces, lower achievable number of mating cycles and shorter contact life. Minimum compression causes higher higher contact resistance and limits current load capability. Most commonly the best suited value in this trade off is determined in application testing.

The basic features of a contact band are made up by

  • the width of the band
  • the thickness of the band
  • the pitch of the contact bridges (number of contact points over defined length)
  • the height of the contact spring elements
  • the length of the band is dependent upon its use

It is important to note that the height of the contact spring elements in their virgin (not yet compressed) state will differ from their height after the first few compression cycles.
This difference is referred to as  “spring setting” and it is a typical behavior for any type of spring.
After about the first 5-10 compression cycles the spring will reach its working height and should remain close to this height until end of life.

Continue reading on how to calculate nominal current rating ....

louvered contact band for every fprm of connector design

press in louvered contact socket for power take off in busbars

Louvered Contact Band
- Nominal Current Calculation

The following examples will show how to determine the nominal performance rating of a  High Current Contact for two different types of weftron.com Louver_tron inserts when used with different metal components.

In the example the louvered band is installed inside a socket with a mating pin diameter of 25mm
=> Lay flat length of band = π25 => layflat length is78.5mm

Determine the number of contact bridges that will fit the socket:

Louver_tron 313 has a contact spacing of 2mm  => 40 * contact bridges for a diameter 25mm socket.
The performance rating for Louver_tron 313 with a material thickness 0.2mm = 30A/ bridge
when used with silver plated components made of ECU copper.

Louver_tron 317 has a spacing of 2.5mm => 32 * bridges for a diameter 25mm socket.
The performance rating for Louver_tron 317 with a material thickness 0.2mm = 27A/ bridge
when used with silver plated components made of ECU copper.

Calculate nominal performance ratings:

Louver_tron 313 will have a nominal performance rating of 40 times 30A =
1200A when used with copper/silver components**
900A when used with aluminum/silver components**
720A when used with brass/silver components**

Louver_tron 317 will have a nominal power rating of  32 times 27A =
864A when used with copper/silver components**
648A when used with aluminum/silver components**
201A when used with brass/silver components**

Conclusion:
Due to the tighter contact spacing and superior contact bridge design***  Louver_tron 313 will allow for higher performance rating on the same connector footprint.

 

* for applications in sockets the result of layflat length divided by spacing will be rounded up to the next whole number. When installed on a pin the result will be rounded down.

** with conductivity factor of 1 for copper, 0.75 for aluminum, 0.6 for brass
values are for reference only based on optimal design and machining parameters @ ambient 20°C
The final performance will need to be established in testing.

***  Louver_tron 313 geometric layout allows for one entry point on the top and two exit points on the bottom of each louver which leads to two current paths/louver. Louver_tron 317 has one entry point on top and one on the bottom.

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