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Achieving a Good Connection - Part 1

Electrical connections come in two forms-end terminations and joints between two conductors. A good electrical connection is one that is able to conduct current safely at a low temperature, resulting in energy savings and should last for many years (30 years or even longer). But how can you ensure and achieve a good electrical connection every time?

Generally there are three important factors in executing a good electrical connection:

  1. Type of Connectors

  2. Crimping Tools and Dies used

  3. Workmanship

‚ÄčIn this part we will look at why the right connectors is necessary to achieve a good connection. 

 

 

Copper Conductors

 

Copper connectors are used to join or end a Copper conductor. These connectors are made of Copper that comes in a high conductivity copper tube with suitable thickness. A lug will have sufficient palm area and barrel length, whilst a link should have sufficient link length, and plated with Tin to prevent corrosion.

 

Copper has many grades. For electrical purposes, the Electrolytic Copper (E.Cu) with purity 99.9% and conductivity 99% I.A.C.S. is always used.

 

Using low quality recycle copper is not recommended, as the conductivity is 50% to 85%. For the same size of cable lugs, when conductivity is low and the wall thickness is less, the current capacity of the cable lug is greatly affected.

 

Currently there are many type of cable connectors imported into Malaysia, some of which are either not suitable to Malaysian cables, or may be inferior in quality. This may result in high temperature (energy loss) at the connections, or even burning the connectors. The only way to prevent this is to use a standard. With this in mind, the Malaysian Standard was developed and obtained during year 2002, MS1540 for Cable Lug and later MS1779 for Cable Link in year 2005.

 

In order to avoid unnecessary problem, the Malaysian Standard should be specified during the purchase cable lugs or cable links. Engineers and planners have the responsibility to specify cable lugs or links that comply with the Malaysian Standards. Users too, should insist on buying the right cable lugs and links so that the connection will be at an optimum temperature, resulting in safety and energy-saving on the connections.

 

 

Aluminium Connectors

 

Aluminium connectors are used to join or end terminal of Aluminium conductors. The Aluminium Bi-metal connectors on the other hand are used solely to join or terminate to Copper.

 

The right Aluminium connectors to use are those with electrical grade Aluminium raw material 1050 or 1350. It has purity level of 99.5%, and conductivity is at 60%. Its hardness is soft. Non-electrical grade Aluminium, due to its low purity, has conductivity of only about 40% to 50% or even lower. Its hardness is also wrong, resulting in the Aluminium cracking during the crimping process. Therefore it is important to check and insist on electrical grade material when purchasing Aluminium connectors. 

 

When it comes to conductivity, Aluminium is the best alternative to Copper in terms of commercial value and engineering properties. Compare to Copper, the specific gravity of Aluminium is only a third but its electrical conductivity is up to 60% of Copper. Aluminium is also 70% cheaper than Copper. Due to its lightweight and low cost relatively, Aluminium conductors are widely used in electrical projects today.

 

However, Aluminium that comes in contact with Copper can cause corrosion in a short span of time resulting in a damaged contact. Since Aluminium and Copper have different electrical potential and expansion ratio, the hot and cold cycle with exposure to air will increase resistance and corrode the contact. This phenomenon is known as the coupling effect.

 

In the absence of proper connectors, many Aluminium conductors that were installed in the early days have been found to breakdown after a short period of operation. This has caused the consultant engineers to shy away from approving the use of Aluminium conductors, making it less popular to be used for indoor electrical wiring.

 

This however has changed with the introduction of friction welding type Bi-metal connectors, which are now widely used. The Bi-metal connector is today the best solution to solve the contact problem between Aluminium and Copper.

 

Aluminium and Copper are fused in the process called friction welding. This is done by spinning Aluminium and Copper on a machine to allow the metals to rub against each other to produce high heat. During this stage, a strong force is applied to weld the two metals together. A good quality friction welding has the two metal surfaces sealed perfectly without any air gaps, which will prevent corrosion on the contact. A good and sufficient welding area also contributes to mechanical strength of the connection.

 

In the international market, quality Bi-metal connectors are mainly produced from Europe. Its dimensions are in compliance to France standard NS 68-S-90 titled “Connection of Aluminium Conductor Insulated Cables by Deep Indentation” and type tested to IEC 61238-1 titled “Compression and Mechanical Connectors for Power Cable for Rated Voltages up to 30kV”. TNB and Malaysia also adopt the standard and the type test.

 

Many Bi-metal connectors are imported into Malaysia. Some are quality products; however there are many inferior ones as well. Therefore it is important to select a Bi-metal connector that is compliant to the above standards and type test before it can be considered and accepted as very safe to be installed in a project with Aluminium conductors. 

 

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