Vpliv električnega obloka na lastnosti Cu kontaktov s kositrovo prevleko

Šumandl, Patrik (author)

V diplomskem delu smo obravnavali pojave med vklopom stikalaelektričnega tokokroga nizkih napetosti v odvisnosti od materiala kontaktne površine stikala ter spremembe v mikrostrukturi kontaktnega materiala po vklopu/izklopu električnega tokokroga s tokom visoke jakosti in nizke napetosti. Za material kontaktne površine smo si izbrali čisti dezoksidiran baker ter pokositren čisti dezoksidiran baker. Pojavi, ki se dogajajo v začetni fazi vklopa/izklopa električnega tokokroga vključujejo predvsem odbijanje kontaktov, izparevanje, ionizacijo in prenos materiala med kontaktnima površinama, tvorjenje oblokov in posledično tvorjenje zvarov kontaktnih površin. Za zaznavanje pojava odboja kontaktnih površin pri vklopu električnega tokokroga smo uporabili elektronski osciloskop in merili spremembo napetosti v času vzpostavitve električnega tokokroga pri obeh izbranih vrstah kontaktnega materiala. Na ta način smo ugotavljali kako vpliva sam material kontaktne površine na čas, ki je potreben za vzpostavitev tokokroga, ter na število odbojev kontaktnih površin. Skonstruirali smo tudi napravo za premostitev električnega toka visoke jakosti preko kontaktnega sklopa s katero smo simulirali dogajanje pri tako visokih jakostih električnega toka, da so povzročile zavaritev kontaktnih površin in uničenje stikala. Ker so nas zanimale specifične lastnosti obeh vrst materialov smo med izklopom električnega tokokroga merili tudi UI karakteristiko. Po opravljenem vklopu/izklopu stikala smo s svetlobnim in elektronskim mikroskopom preiskovali mikrostrukturne spremembe materiala kontaktnih površin.

• Language: Slovenian
• Keywords: Bakren kontaktni material, pokositren bakren kontaktni material, pojavi pri vklopu/izklopu tokokroga, električni kontakti.
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2019
• PID: 20.500.12556/RUL-111504
• COBISS.SI-ID: 1846111
• Publication date in RUL: 02.10.2019

Secondary language

• Language: English
• Title: Effect of electric arc on the properties of the Cu contact with tin coating

Abstract

The diploma work deals with the phenomena during switching the low voltage electrical circuit depending on the material of the electrical contact surface as well as changes in the microstructure in the contact material after braking the electrical circuit with high current and low voltage. As the contact material pure deoxidized copper and tinned pure deoxidized copper have been chosen and investigated. The phenomena occurring in the initial stage of making the electrical contact include contact surfaces bouncing, the evaporation, ionization, and transfer of material between the contact surfaces, the formation of arcs and the consequent formation of welds of the contact surfaces. We used an electronic oscilloscope to detect the occurrence of contact surface bounces, by measuring the voltage change during the initial stage of establishing the electrical contact. In this way, we could determine how many times contact surfaces bounced between each other and how the material of the contact surface influences the time required to completely establish the electrical circuit. We also designed a device for bridging high-current through a contact assembly, which simulated events at such high currents that caused contact surfaces to be welded and the switch destroyed. Because we were interested in the specific properties of both types of materials, we also measured the UI characteristic during breaking the electrical contact. Microstructural changes in the contact material were also analyzed with light and electron microscope after breaking the high current electrical circuit.

• Keywords: Copper electrical contacts, tinned copper electrical contacts, make/brake electrical contacts, phenomena during making/breaking electrical circuit.