2.2.1 Reasons for poor electrical contact

Changes in electrical contact materials. Electrical contact materials, especially switch contact materials, have strict requirements for their conductivity, hardness, etc. If the original electrical contact materials are not replaced appropriately, it will inevitably affect the performance of electrical contacts. Secondly, in order to compensate for the defects of certain electrical contact materials, a layer of other metals such as silver, tin, gold, etc. is often plated on the surface of the electrical contact material. During the repair process or prolonged wear and tear, if the coating is damaged or disappears, it will inevitably deteriorate the electrical contact performance.

Changes in the form of electrical contact. Due to various reasons, the unevenness of the electrical contact surface or the displacement and direction change of the contact surface can lead to changes in the form of electrical contact, such as changing from surface contact or line contact to point contact, or from point contact to surface contact or line contact, which may result in poor electrical contact.

The reduction of electrical contact pressure. The deformation of the spring and inadequate transmission mechanism result in a decrease in electrical contact pressure. This is one of the important reasons for poor electrical contact.

Electrochemical corrosion caused by direct connection of copper aluminum conductors. The direct connection between copper and aluminum conductors forms an electrochemical pair with a high potential difference between copper and aluminum ions, which inevitably leads to electrochemical corrosion. In practical work, it is quite common to directly connect copper aluminum conductors without any treatment. Over time, electrical contact failures are inevitable.

Poor electrical contact surface performance. For various reasons, the electrical contact surface is covered with a layer of materials with poor conductivity, such as metal oxides, sulfides, etc., whose resistivity is far greater than that of the original metal. It may also be dust, dirt covered on the contact surface or oil film, water film sandwiched between the contact surfaces, which forms the surface facial mask resistance. Its existence increases the contact resistance value or causes unstable contact resistance, and even disrupts the normal conductivity of electrical contact connections.

The impact of environmental factors. Dampness, high temperature, and the influence of environmental factors such as acid, alkali, sulfur oxide, and chlorine gas accelerate the chemical corrosion, electrochemical corrosion, and other changes of electrical contact materials.

The electrical contact installation process does not meet the requirements. There are different installation process requirements for different types of electrical contacts, and failure to meet the specified process requirements and standards can result in poor electrical contacts.




Article compilation: Jiangmen assembly line www.zs-chsb.com