AlCubar profiled rail busbars – change ideas

Rails family AlCubar
From the days when the low-voltage switchgear used simple, painted aluminum flat busbars nothing has changed, except that today dominate the flat copper busbars. People have seen many disadvantages in aluminum: too soft electrical conductor, cannot withstand high short-circuit currents, kneading of aluminum joints, that cause subsequent overheating. Oxidation, cracking, and low conductivity of electricity in relation to copper. Is that true?
It is said that the conductivity of aluminum is only 66% of the conductivity of copper - yes, if we take into consideration the conductivity of the cross-sectional area. However, aluminum is much lighter: 2.7kg / dm3, while the copper weighs 8,9kg / dm3. Increasing cross-section * 1,508 we get the same conductivity of aluminum. Now the needed volume of the conductors, with the same nominal currents we need 4kg / dm3 of aluminum, and 8,9kg / dm3 of copper. So aluminum is twice lighter! Comparing the prices of raw materials, where copper is more than twice as expensive, it follows that aluminum is not by half, but four times cheaper!!! So why there is domination of copper in the LV switchgears? Many manufacturers from decades develops theirs own electrical conductors, for example cuponal that are still rectangular flat bars, with plenty of copper around the aluminum core of conductor, unfortunately this solution is not much lighter and much cheaper – mostly up to 20% cheaper. In addition, for example, for rated current 2500A to use cuponal conductor we have to use 2x100x10 rail instead of copper bars 2x80x10. The increase of this dimension means that we will not be able to connect most of such cuponal rails to the breakers designed for copper bars 80x10. There were also developed various types of profile rails, copper, or aluminum. For the first type the only advantage could be ease of connection, because most often it is C-shape rail, where special screws gives the possibility of connecting the output circuit anywhere. However, the price of copper profiled rails is very high and manufacturers of switchgears prefers to make holes punching even at the entire length of the usual flat copper. The second type is the profiled aluminum rail, which gives the same flexibility to connect, however, creates problems with connecting to copper flat busbars - you have to use cuponal washers. In addition, there is a question, what with the aforementioned disadvantages of aluminum?
Coppery coupler for a profile AlCubar
Copper coupler 100x10 for a AlCubar 2500A profile
Aluminum oxidizes - yes! Best to use anodized profile which simultaneously has a larger hardness, corrosion resistance, higher thermal emissivity than copper, anodized coating further improves the electrical insulation and aesthetics. Aluminum is soft or crack - not necessarily! Today's aluminum-magnesium-silicon alloys are giving twice the stiffness of copper, thereby theirs short-circuit withstand is higher, and there is no kneading of aluminum at joints. Because pure aluminum profile has its disadvantages, and the anodized surface is an insulator, the best option is to cover the rail at the contact with a thin layer of copper. Different technologies of surfacing by copper have been known for decades. In the market from many years there are profiled aluminum busbars, coated partly with copper, so why the copper busbar still dominates?
Zenex as a manufacturer of Zenergy switchgear system, aiming to continuously improve the quality and price competitiveness has developed a system AlCubar profiled rails, which we believe has ruled out all the disadvantages of earlier solutions, and used up the advantages of aluminum. Cuponal solution is not perfect – same as copper bar bending possibility is advantage, but causing trouble with the size and a small profit in price. Conclusion is that connecting apparatus like ACB or MCCB still need to be made by flat copper busbar, which is easy forming and has the smallest dimensions. There is no possibility to develop a copper profiles that would be convenient in connection but not extremely expensive, as well as cannot use pure aluminum posing problems with connection. That is why we focused on rigid anodized aluminum profiles, coated with copper. Dedicated exclusively on the straight sections of switchgear system internal busduct. The important thing was to develop a profile shape, that would be easily connectable between it, giving the possibility to mount in standard insulators, and connect without any complicated fasteners intermediary with flat copper bars. The biggest drawback of existing profiles so far is illusory profit - producers set market price around 30% cheaper than the price of a standard flat copper busbar. Unfortunately, these profiles are available in certain lengths, mostly two-meter, which when installed in the switchgear have a useless waste that absorbs theoretical profit. The only remaining ease of installation is that the profiles contain a groove providing the possibility to insert the screw in any place. However, the already known solutions are usually with only one T-shaped groove. For example, for a profile of rated current of 2500A it is very difficult to connect in one place two copper bars 80x10. Also there is the need to use special shaped copper connectors to connect neighboring fields. Such solution in fact is having so much drawbacks, that appears much more expensive than standard copper busbars solution.
Straight connector for a profile AlCubar
Straight 50x10 copper connector for 1000A AlCubar profile
Therefore, during development of a profiled rail AlCubar 2500A we focused on how to develop an electrical conductor that unfortunately must have a larger cross-section and have availability to connect directly two copper busbars in one place, and maintain proper clearances between the individual phases. The solution is two-sided, and even as additional option can be connected by four flat copper busbars, which had none of previous profiled busbars manufacturer. In our solution two-sides groove connection does not require a thicker electrical conductor, which in most cases you cannot afford due to the width of small phase distances in switchgear panel. It has appear that the most important was shape of the profile.
Connecting the main switch two copper rails
Two sides connection to AlCubar by copper rails 80x10
Minimal size has been achieved by making it symmetric by the midpoint of the profile, with offset between the grooves in case of largest cross-section.
Profil AlCubarCross section [mm2]Cross section relative to CuCircuit [mm]Circuit relative to CuThe mass relative to CuEquivalent to copper bus bars

bilateral connection
Bilateral connection of 2x80x10 mm busbars
It appeared that additional 8mm thickness, which takes AlCubar comparing to two flat copper 80x10 with 10mm spacing, for the current interval 2500 is only advantage! Because of it thickness short-circuit withstand is much higher in comparison with flat copper busbars. Advanced profile shape also significantly increase the heat dissipation surface area so the temperature increases are less than their copper counterparts. The breakthrough fact which brings a significant gain for the customer is that we deliver profiles in any length, specified by the customer without cutting costs, so that the client does not have any waste. Additionally we developed specific insulators dedicated to Zenergy switchgear that the customer can connect simple copper connector between the fields of the switchgear, just as it is done in the case of copper busbars.
AlCubar profiled rails
AlCubar profiled busbars: Dimensions and references

Taking into consideration the costs of the entire system, including insulators, special screws to connect the profiles, and copper connectors, for 2500A switchgear rated current with AlCubar is:
  • more than 50% lighter
  • 40% cheaper material

Moreover, the system AlCubar significantly reduces installation time by eliminating laborious copper bar cutting and punching. Another advantage is the possibility of making additional connection of output circuit anywhere, anytime even at short maintenance breaks. In the case of copper bridges it is often very difficult, or it require removal of the busbars from switchgear for modification. The AlCubar system provides several fastening elements in the form of a hammer screws, T-slot nuts that can provide connection of the output circuits anywhere along the rail AlCubar without removing adjacent existing connections. Also there are used sets from single till quadruple screws for fast and reliable (reinforced) connection between AlCubar profiles, or for output circuits.