Discover about the structure of the Busway

Regarding the shell structure, the busway is usually made from aluminum shell, iron shell or iron aluminum shell.

– The structure of the busway of PPB LS Cable and GE produced in the US uses a 2-piece cast aluminum shell with electrostatic paint. LS Cable, GE USA, GE China, MM Hongkong, Siemens Vietnam use a 4-piece aluminum shell to produce the busway. When connecting, the 2-piece aluminum shell needs two rows of screws, while the 4-piece aluminum shell needs 4 rows of screws or rivets to fasten.

– The 2-piece cast aluminum shell in the world is only available from LS Cable and GE produced in the US (GE produced in China uses a 4-piece aluminum shell). In principle, when manufacturing 4 pieces, it will be very easy, but because it has to be connected to 4 rows of screws, it is not as secure as a 2-piece aluminum shell (only need to connect 2 rows of screws). Currently, the world’s leading brands such as Siemens, LS Cable, GE, Cutler Hammer have all switched to aluminum housing technology for the past 5-6 years.

Iron housing: Including Henikwon, Translite, Megaduct manufacturers

Schneider, a product manufactured in China, is offered to Vietnam to produce 2-piece aluminum and 2-piece iron busway conductor bars. Due to the superiority of aluminum housing compared to iron housing, major companies have eliminated iron housing and instead manufactured aluminum housings for the past 5-6 years:

– Iron is much heavier than aluminum, so when hanging, aluminum-clad conductor bars are safer

– Iron radiates less heat than aluminum, so when using iron housing, the conductor system is hotter and loses more energy, the rated current is reduced compared to the design.

– Iron conducts electricity worse than aluminum, so using iron housing as a grounding electrode will only reach a maximum of 50% E. While using aluminum housing can reach over 100% E.

The conductive core, in principle, can only be aluminum (AL) or copper (CU), with a purity of up to 99.99%. The characteristic of copper is that the conductivity is greater than 99%, aluminum is 63-67%, so in return, when using aluminum, a bar with a larger cross-section must be used, but aluminum is still lighter and cheaper, when operating at the same current.

In the past, due to the habit of using electric cables, most customers in Vietnam used copper. From the end of 2007 to now, due to updating information on the world market, the number of projects using aluminum bus ducts has increased significantly.

Copper cables are flexible so they are easy to bend, but the busbar does not need to be bent, so using aluminum cores in commercial buildings is most suitable, because the larger size is not significant, but the price is generally 30% – 50% cheaper (depending on the amount of accessories, because the labor cost of accessories is generally the same for both copper and aluminum busbars).

Manufacturers have classified the projects that should use copper busbars as: Hospitals, data centers, semiconductor factories, research centers and high-tech centers, etc. All commercial buildings should use aluminum due to its efficiency and cost savings while ensuring the same life as copper core busbars.

In addition, due to manufacturing characteristics, some manufacturers only have aluminum bus ducts up to 4000A, not 5000A or 6300A. In this case, we often recommend using copper to avoid competition with other companies when they have large aluminum bus ducts (customers do not benefit from such offers, but have to pay very high prices for copper bus ducts when using large operating currents).

In Korea, Japan, and European countries, almost 100% of commercial buildings use aluminum, which is 30% cheaper, lighter, and has negligible losses compared to copper, with a voltage drop almost equivalent.

According to the regulations of IEC 60439-1/2, the temperature of the busbar is not allowed to exceed 95 degrees Celsius (and not exceed 55 degrees Celsius above the ambient temperature, and also not exceed 90 degrees Celsius). All companies use insulating materials that exceed this standard. Therefore, using the common heat-resistant material of 130 degrees Celsius is far beyond the IEC standard. Different materials also have different heat resistance: Polyester 130 degrees C, Mylar 150 degrees C, Epoxy from 130-170 degrees C (depending on additives).

The busway conductor bar was used starting around 1980. At that time, the insulating material was Polyester (large, then folded, and taped). but it could be used well in Europe, Korea, and Japan because the air humidity was lower than 60%. Later, the American Dupont Group produced Mylar material for manufacturers to use to wrap the conductor bar in 2-3 layers. This material reduces the humidity of the conductor bar. However, due to the nature of this material, the insulation is not high (after installation, it only reaches 5-12 Mega Ohm). So American manufacturers researched and used Epoxy as an insulating material for the conductor, and forced the companies selling in the US to use Epoxy because of the following outstanding characteristics:

– The insulation is twice as high as Mylar (after installation, it reaches 20 – 50 Mega Ohm)

– Epoxy’s lifespan is from 50-70 years (because Epoxy is a traditional insulating material and its lifespan is confirmed), but besides Mylar, no one dares to confirm its lifespan, but in fact, it has been over 40 years and Mylar is still working well.

Epoxy adheres tightly to the conductor into a block, with very good water resistance. However, when the conductor is soaked in water, both Epoxy and Mylar will have problems.

But manufacturing Epoxy by the dipping method (fluidizing) requires a technological chain and the secret to mixing Epoxy with additives, so that it adheres tightly to the conductor and has flexibility. Therefore, only American Epoxy technology meets the standards. GE, SIEMENS, SCHNEIDER, Cuttler Hammer all have to produce Epoxy in the US (only Schneider adds Mylar option for customers). LS Cable, wanting to export globally, bought American Epoxy technology and hired all American and Dutch Epoxy engineers who worked for GE and Schneider in the US to Korea to convert to Epoxy technology according to American technology.

After 3 years of mass sales, this technology of LS Cable has proven to be of very high quality and similar to GE USA. At the same time, the 2 companies LS Cable (manufactured in Korea) and GE (manufactured in the US) by manufacturing Epoxy insulation material and 2-piece cast aluminum shell, achieve the highest short-circuit current of 1s and 3s in the world, up to 200kA for 4000A or more (confirmed by Asta, Kema centers and recorded in the catalog).

(Note: The busway made by GE in China that is being sold in Vietnam has a 4-piece aluminum shell and uses Mylar material, which has a much lower short-circuit resistance than the GE made in the US)

Hopefully, through the above article, customers have gained more knowledge and information about busways and their structure!