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General knowledge about copper for busbars


The busbars from the Latin "OMNIBUS" means For All. In electrical engineering term "Bus" used to describe the whole point of many circuit. In general, it means the total point of circuit with a low input voltage and with high output voltage. The power supply or circuit control panel in the current must be able to receive and output for electrical current in large quantities. Large amounts of electrical current can cause large amounts of electromagnetic force as well. Busbars is same as any other electrical equipment with to withstand energy them. The metal is used as a bus bar must have good mechanical and electrical properties. With can be assigned to work at special temp.

The metal is used as a busbar. Should have the following properties.
  1. Have low resistance.
  2. High mechanical strength in tensile. Compressive strength and tear strength.
  3. Fatigue Failure of high resistance.
  4. The low resistance of the Surface Film.
  5. Cutting and bending mobility.
  6. The high corrosion resistance.
  7. Low price.

Considering all of these features can be seen that copper is the metal best suited for use as busbars and aluminum metal as the next.

Typical relative properties of copper and aluminium

Properties of copper and aluminium can be compared to the following table.



Bar the means line with rectangular cross section. Thickness of 0.5 mm or more and a width not exceeding 160 mm.


     The tolerances and mechanical properties for a larger size are according to the agreement between the purchaser and manufacturer.


Type of copper bars
    The industrial products standards of bars copper are divided 3 categories.
          1. Annealed type
          2. Half - hard type
          3. Hard type



       Bars copper and copper wire must to be produce from the high conductivity copper (High conductivity copper) of any kind. The chemical composition according to the following table.

     1.  Electrolytic touch pitch type
    2.  Fire-refined touch pitch type
    3.  Oxygen-free type
    4.  Oxygen-free for special applications type


The table shows the chemical ingredient of high conductivity copper



      1.  Limit quantity of the oxygen is 0.06 % by weight of the casting in the vertical. And limit quantity of other impurities are the agreement between the purchaser and manufacturer.               
     2.  Ratio of the silver are mixed with copper (Silver-bearing copper) typically, the silver might be the percentage 0.03 to 0.2 of weight, buyers should request specify the silver ratio by use.
     3.  Volatile compounds including Arsenic Antimony  Bismuth Cadmium Manganese Selenium Tellurium and Zinc might be the percentage 0.0025 of weight. Unless otherwise agreed between the purchaser and manufacturer.

Characteritics of copper Busbars

     1.  Appearance must be clean, smooth and free from defects invisible to the eye.
    2.  Electrical resistivity and conductivity. Seen from the table.


The table shows the electrical resistance condition and electrical conductivity condition    


     State power is compared to the percentage of annealed copper standard established by Internation Electrotechnical Commission. That copper has a volume resistivity at 20 oC was 0.017241 ohm per meter square millimeter. The electrical conductivity of the 100 (IEC 28)

3.  Mechanical properties
   3.1  Tensile strength
          Copper rod and copper with tensile strength as determined by reference to standards industry products (TIS 408-2525)
          or refer to the standard of Japanese industrail standard (JIS).
   3.2  Elongation
         Copper rod and copper wire must be stretching to refer to the industry standard (TIS 408-2525) or refer to the standard of Japanese industrail standard (JIS).
         Copper bars with a thickness of less than 0.8 mm and a width of less than 5.12 mm in nat to test stretching.
   3.3  The bending of the width
          Copper with a thickness not exceeding 10 mm on the bending of the width of test of method specified. Must be not cracked or broken. Please refer to the industry standard (TIS 408-2525) or refer to the standard of Japanese industrail standard (JIS).
   3.4  The bending of the thick
           Copper rods type annealed with a thickness of less than 10 mm. and a width of less than 30 mm. When the thickness of the bending test method requirements. Must be not cracked or broken. Please refer to the industry standard (TIS 408-2525) or refer to the standard of Japanese industrail standard (JIS).

The table shows the mechanical characteristic of copper bar and copper rod


 Note                    *   So : Cross section area
                             **  Eloggation length at 50 mm.


4.  The durability to brittleness because the hydrogen (Hydrogen embrittlement)
Copper rods and copper wire made of oxygen-free high conductivity copper. Must be the durability to brittleness because the hydrogen without any cracks visible to the naked eye. Please refer to the industry standard (TIS 408-2525), refer to the standard of Japanese industrail standard (JIS), refer of the standard of International Annealed Copper Standard ( IAC ) or refer to the standard of International Electrotechnical Commision (IEC).


Two of the standard fee. May calculate that.


Copper has properties equal to those that have electrical conductivity equal to 100% ICAS for HC copper to produce a modern, mixed with oxygen is reduced. Purity greater than a given value. This allows the electrical conductivity greater than 100% ICAS copper used in electrical work should be in a pure (Purity) due to impurities in the copper has a dramatic effect on the mechanical and electrical properties. The impurities that affect the electrical conductivity depends on the amount and type of metal impurities in copper, such as phosphorus, only 0.04% of the weight of copper will reduce the power down to 80% ICAS is not pure. And oxygen, which should not exceed 0.1% copper with a purity of this is. The high electrical conductivity copper (High Conductivity Copper or HC Copper).

The AC bus bar
          The resistance of the conductor for AC power their value always more than DC power. The magnetic field of alternating current. Will cause the voltage induced. This allows the current in the conductor in the lower right of the conductor. Will be affected most. The magnetic field is higher. And the magnetic field decreases near the surface induced voltage is generated that varied in size and the area of the phase conductors. The greatest value of the center conductor. And decreases when approaching the surface Thus, electricity is more valuable at a low electromagnetic induction at the surface of the conductor. The phenomenon is called the Skin Effect or Edge Effect. The current density is not uniform in the conductor, the resistance appeared to increase. The ratio between the resistances to alternating current to direct current resistance is called the Skin Effect Ratio.


Copper pipe

           Skin Effect in a copper conductor pipe. As a function of the thickness of the pipe wall. The ratio between the diameter and thickness. For the cross-section area requires that. The Skin Effect could be reduced. By increasing the size of Diameter and reduce the thickness down.

Rectangular copper bars

          Skin Effect in the rectangular copper bars as a function of thickness and width of the bar. For the same cross sectional area of a large bar. Skin Effect in a thin rectangular copper bar is less than in copper wire conductor. The Skin Effect depends on the ratio of width to thickness of the bar. The Skin Effect is increased when the thickness increases.

How to connect the busbars.

          Conductors to be connected to the mechanical strength. And have the low resistance at connection point. And constant to the low resistance throughout a lifetime of connection point. The connection with the performance of copper busbars. You can do this by using screw (Bolting) to hold (Clamping) and pins (Riveting) Soldering or the Welding. The connection by using screw and hold are widely used first two are widely used. However, the connection by the copper is being used more and more.

The connection point by welding copper of the busbars have the advantage is ability to electrical conductivity does not change due to the connection point is the same copper.

  • The bolting is a convenient way and reliable. The disadvantage is the need to drill holes into the bar to put the nut. Will cause distortion in the electrical conductivity. This connection point causing the electromotive force at point of connects uneven.

  • The clamping is easy by cross-section area not damage. The mass to increase help cooled at the connection point. The good design for clamping to will the electromotive force constant at point of connect and easy to the setup. But the disadvantage is cost.

  • The riveting is high efficiency. The disadvantage is difficult to remove or to install tightly and installation is not easy.

  • The soldering is used very little for busbars. It must be supplemented by screw or the clamping. The heat from a short circuit can cause electrical and mechanical that is not good.

A great feature of the copper rod and copper wire, Specification for checking  and requirements about copper rod and copper wire as described above. Please refer to the Standard Industrial (TIS 408-2525) or refer to the standard of Japanese industrail standard (JIS).

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