Wear Mechanism of Current Collecting Materials due to Temperature Distribution Analysis Considering Degenerated Layer

Abstract

To clarify the wear mechanism of current collecting materials such as a contact wire and a contact strip under electric current condition, it is necessary to clarify temperature distribution around the contact spot. However, the traditional method of estimating the maximum contact temperature such as the φ-θ theory cannot estimate the temperature distribution. In this paper, we newly proposed an electric field analysis model of hard-drawn copper and iron-based sintered alloy considering a degenerated layer such as an oxide film and wear debris. Then, we newly proposed the heat conduction equation applying the Wiedemann-Franz law, and analyzed temperature distribution in electrodes. As a result, we find that the relation between the maximum temperature and the contact voltage even in dissimilar electrodes are based on the φ-θ theory. The temperature distribution in electrode changes depending on whether or not degenerated layers exist, and the maximum temperatures of each electrode are not necessarily the same as those estimated by the φ-θ theory. Finally, we clarify the influence of the degenerated layer on the melting condition of electrodes, and explain the electric wear phenomena observed in the previous wear test.

Wear Mode Map of Current Collecting Materials

“…According to our previous reports [5,6], it is clear that the melting of respective materials is the important factor for the wear mode transition phenomena under current flowing condition. According to Fig.…”

“…the radius of the contact spot was set to 100 μm. The contact voltage was varied from 0.1 V to 0.7 V. These conditions are the same in previous analysis [6].…”

“…The analysis model shown in Fig. 1 is the same as that reported previously [6]. This model imitates such asymmetric contact as is made between cylindrical electrodes which have a contact spot with the radius of a [m].…”

“…Then the authors clarified that the main factor in increasing the wear of the contact wire is not the arc discharge but the melting bridge [5]. In addition, the authors analyzed the temperature distribution around the contact spot and clarified that its distribution varies by a degenerated layer such as an oxide film on the contact surface [6]. It should be noted that these reports are the case study about the material combination of the hard-drawn copper contact wire and the iron-based sintered alloy contact strip.…”

Influence of Apparent Contact Area on Wear Properties of Hard-Drawn Copper Contact Wire and Iron-Based Sintered Alloy Contact Strip under Electric Current Flowing Condition

“…On the other hand, the authors reported that the theoretical maximum temperature of asymmetric contacts θ max [K] depends on the contact voltage V c [V] and is calculated with following equation [4]. 3where L is the Lorentz number (=2.4 × 10 -8 [V 2 /K 2 ]), and this equation is called the φ-θ theory [5].…”