Analiza staranja termočlena v trajnostni progi : diplomsko delo

Bojanec, Robi (avtor), Geršak, Gregor (mentor)

Termočlen je namenjen za merjenje temperature, ki se giblje od –40 °C do 1600 °C. Termočlen je zgrajen iz dveh prevodniških žic. Na enem koncu je konektor, na drugem pa sta žici sklenjeni. Prav na sklenjenem delu, tam, kjer je zvar, je temperaturni senzor. Ta senzor deluje tako, da je pritrjen na merilno površino, med konci njegovih žic pa zaradi termo napetosti nastane električna napetost, ki se lahko pretvori v temperaturo. Prvo poglavje diplome je namenjeno predstavitvi termočlena tipa K, kako se je termočlen sploh razvil oziroma kako so prišli do same sestave temperaturnega senzorja. Različni materiali prevodniških žic omogočajo različno merilno območje. Nekatere prevodniške žice so zaradi materiala omejene na visoke, nekatere pa na malo nižje temperature. Imamo različne tipe termočlenov, ki jih delimo glede na material prevodniških žic. V drugem poglavju bom predstavil celotno merilno opremo, ki sem jo potreboval za raziskovalno nalogo. Elektromotorni pogon, ki ga razvijajo v podjetju Danfoss Trata, je imel posredno nalogo pri opravljanju meritev, saj sem nanj pritrjeval termočlene tipa K. V podjetju imajo razvojni laboratorij, kjer opravljajo trajnostne teste elektromotornih pogonov. Za trajnostne teste uporabljajo trajnostno progo, kjer se izvajajo cikli pogona za merjenje temperature med obratovalnim stanjem oziroma ciklanjem s termočleni tipa K. Po končanem ciklanju je potrebno termočlen kalibrirati, kar sem izvedel s kalibracijsko kopeljo z mineralnim oljem. Kalibriranje je potekalo tako, da sem v kopeli nastavil temperaturo, ki je bila skozi celotno kalibracijo konstantna. Vanjo sem potopil aluminijaste cevke, v katerih so bili postavljeni kalibrirani termočleni. Podatke sem zajemal ročno z napravo Fluke 744 Documenting Process Calibrator. Tretje poglavje zajema celotno merjenje in kalibriranje termočlenov tipa K. Za raziskavo sem izbral 6 termočlenov, ki so bili pritrjeni na različne dele površine elektromotornega pogona. Po določenih ciklih sem termočlene odstranil z elektromotornega pogona in jih kalibriral. Zanimalo me je, za koliko meritev bi lahko uporabil en termočlen tipa K, ki bi bil pritrjen na elektromotorni pogon in ostal v obratovalnem stanju nekaj dni, pri čemer bi bila merilna napaka še sprejemljiva. Trajnostna proga je obratovala na polni moči, da so bili termočleni čim bolj toplotno obremenjeni in da so delovali pri čim višji temperaturi. Nato sem termočlen odstranil z elektromotornega pogona, ga kalibriral v kopeli z mineralnim oljem, ga spet pritrdil nazaj na elektromotorni pogon in znova zagnal trajnostni test. Kot rezultat končanih meritev bi navedel, da so termočleni prava izbira za večkratno merjenje. Upoštevati je potrebno tudi večkratno pritrjevanje in odstranjevanje termočlena na površino, saj se lahko med čiščenjem termočlena konica, kjer je temperaturni senzor, tudi poškoduje, ker pride do razklenitve žic. Zato bi grobo čiščenje odsvetoval. Termočleni tipa K so se zelo dobro odzvali na merjenje temperature na elektromotornem pogonu v trajnostni progi. Dobro se obnesejo tudi na različnih površinah, so točni in odzivni, kar je zelo pomembno za raziskovanje ali razvoj produkta.

• Jezik: Slovenski jezik
• Ključne besede: termočlen, termočlen tipa K, elektromotorni pogon, kalibracijska kopel, trajnostna proga, ciklanje
• Vrsta gradiva: Diplomsko delo/naloga
• Tipologija: 2.11 - Diplomsko delo
• Organizacija: FE - Fakulteta za elektrotehniko
• Kraj izida: Ljubljana
• Založnik: [R. Bojanec]
• Leto izida: 2021
• Št. strani: XIV, 68 str.
• PID: 20.500.12556/RUL-127645
• UDK: 621.317:621.362.1(043.2)
• COBISS.SI-ID: 68020995
• Datum objave v RUL: 18.06.2021

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Aging effects of thermocouples in durability tests : visokošolski strokovni študijski program prve stopnje Aplikativna elektrotehnika

Izvleček

The thermocouple is intended for measuring temperatures ranging from -40 ° C to 1600 ° C. The thermocouple is constructed of two conductive wires. There is a connector at one end and the wires are closed at the other. The temperature sensor is located on the closed part, where the weld is. This sensor works by being attached to a measuring surface; an electrical voltage is generated between the ends of its wires due to thermal voltage, which can be converted into temperature. The first chapter is intended to present the type K thermocouple, how the thermocouple was developed, and how the composition of the temperature sensor arose. Different conductor wire materials allow for different measuring ranges. Some conductor wires are limited to high temperatures due to the material, and some to slightly lower temperatures. There are different types of thermocouples, which are divided according to the material of the conductor wires. In the second chapter, I will present all the measuring equipment I needed for the research task. The electric actuator, which is being developed at Danfoss Trata, had an indirect task in performing the measurements, as I attached type K thermocouples to it. The company has a development laboratory where sustainable tests of electric actuators are performed. For sustainability tests, a sustainable track is used, where drive cycles are performed to measure the temperature during the operating state or cycling with type K thermocouples. After cycling, the thermocouple must be calibrated, which I did with a calibration bath with mineral oil. The calibration was performed by setting a temperature in the bath that was constant throughout the calibration. I immersed aluminum tubes in it, in which calibrated thermocouples were placed. I captured the data manually with the Fluke 744 Documenting Process Calibrator. The third chapter covers the entire measurement and calibration of type K thermocouples. For the research, I selected 6 thermocouples that were attached to different parts of the surface of the electric actuator. After certain cycles, I removed the thermocouples from the electric actuator and calibrated them. I investigated how many measurements could be performed using one type K thermocouple, attached to an electric motor drive and operated for a few days, whilst the measurement error remained within an acceptable range. The sustainable line was operated at full power so that the thermocouples were as heat-loaded as possible and that they operated at the highest possible temperature. I then removed the thermocouple from the electric actuator, calibrated it in a mineral oil bath, reattached it back to the electric actuator, and ran the sustainability test again. As a result of the completed measurements, I would state that thermocouples are the right choice for multiple measurements. Repeated attachment and removal of the thermocouple to the surface must also be considered, as the thermocouple tip, where the temperature sensor is located, can also be damaged during cleaning due to wire breakage. Therefore, rough cleaning would not be advised. Type K thermocouples responded very well to temperature measurement on an electric actuator in a sustainable line. They also perform well on a variety of surfaces, are accurate and responsive, which is very important for product research or development.

• Ključne besede: thermocouple, thermocouple type K, electric actuator, calibration bath, durability test bench, cycling