一、This paper expounds the causes of contact resistance
The additional resistance is the sum of the contraction resistance and the surface film resistance, which is due to the direct resistance generated between the contact layers. Therefore, the additional resistance Rj is called the contact resistance. The contact resistance also exists when the moving and stationary contacts are in contact
二、Types of contact resistance
1. Contraction resistance
No matter how carefully the surface of the contact is processed, from the microscopic point of view, the surface is always uneven. They are not in contact with the whole area, but only a few small protuberances are in contact. As shown in Figure 3-5, the actual contact area is much smaller than the apparent contact area. When the current passes through the actual contact area, the current only passes through the contact points. Near these contact points, the current line is forced to contract. Since the effective contact area (i.e. the actual contact area) is less than the apparent contact area, the additional resistance generated is called shrinkage resistance.
2.Surface film resistance
For various reasons, the contact surface of the contact is covered by a thin film of poor conductivity, such as metal oxides and sulfides. It has poor conductivity. It may also be dust or dirt falling on the contact surface or oil film and water film sandwiched between the contact surfaces. The additional resistance thus formed is called surface film resistance. A kind of
The size of the surface film resistance is related to the type of the film, but also to the thickness of the film. The thicker the film, the greater the resistance.
三、Factors affecting contact resistance
1、Effect of contact pressure
The contact pressure has the greatest influence on the contact resistance. When the contact pressure is very small, the small change of the contact pressure will make the contact resistance fluctuate greatly.
2、Influence of contact material
The influence of contact materials on contact resistance mainly depends on the resistance coefficient, compressive strength and chemical properties of contact materials.
3、Influence of contact temperature
The contact resistance of contact is affected by temperature as well as its metal resistance. With the increase of contact temperature, the contact resistance increases. The relationship between the contact resistance and the temperature is known from the test
4、Influence of contact temperature
The contact resistance of contact is affected by temperature as well as its metal resistance. With the increase of contact temperature, the contact resistance increases. The relationship between the contact resistance and the temperature is known from the test
