An evaluation method of the contact erosion based on the DC mode test of electromagnetic contactor

Electrical contacts are widely used for telecommunication and electric power systems as a device mechanically making and breaking electrical current. In the future, they can be still indispensable. Furthermore, the performance and reliability of electrical contacts must be more improved. Details of the mechanisms, however, have not completely been revealed yet, so that contact erosion and material transfer sometimes lead them to contact failure. We focus on two issues about contact erosion. In these years, volumetric method was proposed as the new evaluation method of surface erosion. However, few papers compare it with weighing method of measuring the mass change in detail. Hence, we investigated relationship between the number of switching operations and the amount of wear in electromagnetic contactor, and compared two methods. Furthermore, electromagnetic contactor is often used in the systems with an AC power supply. On the other hand, the DC mode test provides more fundamental data for us to investigate the electrical contacts than the AC mode test. We compared the data of the DC mode test with that of the AP mode test and described the possibility to estimate contact erosion with an AC power supply in terms of the DC mode test. The result of the DC mode agreed well with that of the AP mode in the case of low load current and a small operation number. We could also show an availability of volumetric method in early lifetime prediction.