Effect of Electrical Load on Contact Welding Failure of Silver Tin Oxide Material Used in DC Electromechanical Relays

Xu Zhang,Shujuan Wang,Wanbin Ren,Zhe Zheng

doi:10.1109/access.2019.2940966

Xu Zhang, Shujuan Wang + Show 2 more

Open Access

https://doi.org/10.1109/access.2019.2940966

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Abstract

In order to clarify the contact welding failure mechanism of DC electromagnetic relay, a series of electrical endurance tests are carried out with the use of silver tin oxide material under resistive and capacitive load conditions. The typical waveforms of contact voltage and contact current during making and breaking resistive load and capacitive load (load capacitance of 1mF, 1.5mF, 2mF and 2.5mF) are obtained by the designed model switch. Further, the variations of sensitive electrical parameters such as bounce energy, contact resistance, static contact force and break arc energy during electrical endurance test are analyzed explicitly. It is found that the variations in sensitive electrical parameters is closely related to the electrical load type. In particular, under the capacitive load conditions, the sharp increase of each sensitive electrical parameter in the end of lifetime prognosticates the dynamic welding failure of silver tin oxide contact material. Finally, with the help of SEM (Scanning Electron Microscope) pictures of failed contacts, the surface erosion features of contact materials are mainly determined by the competition between the cathode arc and the anode arc. And the material transfer and distribution are the root reason for the contact welding failure of DC electromechanical relays.

Highlights

Nowadays, silver based materials, including silver cadmium oxide Ag/CdO, silver tin oxide composite Ag/SnO2, silver nickel AgNi, silver graphite AgC and so on are widespread used in all kinds of low voltage apparatus for switching current [1]–[3]
We define the product of contact voltage and contact current in terms of contact bounce is the bounce energy, it is written by t1 n t0 uidt = UiIi i=1 t=
In this paper, the variations in bounce energy, contact resistance, static contact force and break arc energy of silver tin oxide contact material are recorded with the use of designed model switch during the electrical endurance test

Summary

INTRODUCTION

Silver based materials, including silver cadmium oxide Ag/CdO, silver tin oxide composite Ag/SnO2, silver nickel AgNi, silver graphite AgC and so on are widespread used in all kinds of low voltage apparatus for switching current [1]–[3]. Long-term stable performance of electrical contact materials is a fundamental precondition for reliability and lifetime of electronic and electrical application It is top-urgent to understand and determine the failure mechanisms of silver tin oxide composite material used in switching devices. The influence of mechanical parameters of switching devices and manufacturing process and methods of contact material in erosion resistance performance could be investigated with such kind of model switch. The multidimensional data (including bounce energy, contact resistance, static contact force, break arc energy), which could characterize the degradation process of relay and contact material, are collected in real-time and analyzed explicitly during the electrical endurance test. B. EXPERIMENTAL CONDITIONS A series of electrical endurance tests are conducted to investigate the effect of capacitive load on contact welding of silver tin oxide type contact material.

RESULTS AND DISCUSSION

FAILURE MECHANISM ANALYSIS

CONCLUSION