Abstract
Contact resistance is an important maintenance parameter for electromagnetic switches, including low-voltage relays. The flow of significant current through electric contacts may influence the contact surface and thus the value of the electric contact resistance (ECR). The change in ECR is influenced not only by the value of current but also by the current phase. Therefore, the impact of the switching short-circuit current’s phase on the ECR was analyzed in this paper. Significant changes in the resistance after each switching cycle were observed. The ECR decreased significantly after each make operation, and a correlation with current amplitude, total let-through energy, and short-circuit time was not observed.
Highlights
Low-voltage relays are commonly used to connect circuits with moderate switching currents.They have found an application mainly as executive elements in building automation systems [1,2]that are becoming more and more popular, as well as in programmable controllers [3,4]
The results of this study are helpful in assessing contact materials used in low-voltage relays as they indicate how the contact resistance may change while switching fault current
These phenomena may include the occurrence of overload currents and short-circuit currents that, as they flow through the relay contacts, can affect their surface condition and, the value of the contact resistance, which is an important operational parameter of the relay
Summary
Low-voltage relays are commonly used to connect circuits with moderate switching currents. They have found an application mainly as executive elements in building automation systems [1,2]. Research presented in referenced literature focuses either on different materials, like Ag-W, or higher test currents, over 1 kA, and contact force up to 50 N. It seldom touches upon the issues related to lower static contact force, in the range of centinewtons together with voltages up to 230 VAC and test currents reaching 300 A. Electrical surface contactmodel model with with asperities contact areaarea [8]. [8]
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