|
|
DC arc extinguishing in low voltage switching devices for critical currents
Fencl, Martin ; Šimek, David (referee) ; Píška, Jakub (advisor)
This bachelor’s thesis deals with DC arc extinguishing for critical currents. The first, theoretical part describes and defines an arc, a DC arc and methods of its extinguishing. The second, theoretical part concerns spectral analysis – specifically, the emission method. Methods of research of extinguishing critical currents are also presented. The practical part consists of two measurements. The first measurement consists of spectrum measuring in time, in conjunction with voltage and current measurements. In the second measurement, the goal was to measure the dependence of arc burning time on voltage and current. The thesis concludes with summary of the results of each individual measurement and their presentation in the wider context.
|
|
|
Remanent magnetism of electromagnets of DC contactors
Horký, Jakub ; Píška, Jakub (referee) ; Šimek, David (advisor)
The master thesis is focused on a remanent magnetism of electromagnets of DC contactors. In the first part of the thesis deals with the formation of a magnetic field in different kinds of materials, description of their magnetization and sorting. The next part is focused on the principle and history of an electromagnet. Negative effects and remanent induction of the contactor are described in the end of the theoretical part. The second part is a practical part. First, the reaction times were measured on a pair of DC contactors. Using the obtained data, an electronic circuit was designed to minimize the difference in switching times of the given DC contactors.
|
|
|
Switching arc diagnostics in DC contactor
Píška, Jakub ; Kloc, Petr (referee) ; Valenta, Jiří (advisor)
Cílem této diplomové práce bylo provést diagnostiku vysokonapěťového stejnosměrného stykače se zaměřením na zpětnou komutaci a lepení oblouku, navrhnout a ověřit úpravy, které odstraní tyto negativní jevy. Měření obloukového napětí, tlaku a pomocí rychlokamery byly použity při diagnostice těchto jevů. Změny na arcrunnerech a jhu magnetického obvodu byly využity při jejich odstraňování. Úpravy na arcrunneru zmenšily skokové nárusty délky oblouku a úpravy na jhu navýšily sílu na oblouk mezi rozevírajícími se kontakty. Navrhnuté změny na stykači snížily časovou ztrátu v důsledku zpětné komutace, a tak zkrátily čas přenosu oblouku.
|
|
|
Contact erosion of switching devices
Píška, Jakub ; Šimek, David (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with the erosion of contacts, as one of the negative phenomena affecting contacts of switchgears. In its first part, it briefly summarizes the other negative influences that must be considered when designing switching devices. In the following part, the physical mechanism of erosion and the primary criterion of assessment - weight loss are approached. The last and main part of the work deals with design of the contact system for comparing this loss for for frequently used materials and testing on a real switchgear. After the tests, the results were analyzed primarily from the perspective of ignition angles, the polarities of the current pulse and the current flowing through the arc. Taking into account the influence of the material composition, the size of the contacts and the presence of the arc-runner.
|
|
|
Back-Commutation And Sticking Reduction Methods In Dc Contactor
Piska, Jakub
The back-commutation and sticking are phenomena which cause an increase in time delaybetween arc ignition and arc reaching the arc chute. These effects cause increase in total switchingtime and contact and arc runner wear. This paper gives a comparison of several approaches to reductionof these effects in a medium voltage contactor for traction usage. The three chosen approacheswere: changes of the shape of the arcrunners, changes of the pole plates of the magnetic circuit andincrease of the ventilation cross section. Metrics on how to compare the performance of these differentalterations were given, based on switching times. From the three tested methods the ventilationincrease yielded the best results as it both reduced the switching time and time delay caused by theback-commutation and reduced the variation of these characteristics.
|
|
|
Comparison Of Arc Erosion Coefficients
Piska, Jakub
The problem of nonunified approaches to giving arc erosion ratios is addressed for the application of molded case circuit breakers (MCCBs) in the range 6.5-10 kA. Charge, Joule’s integral and arc energy are compared as possible quantities to use for ratios of mass loss. The linearity of the relationship of mass loss to those quantities was used as the main metric. By this metric the ratio to charge was chosen as the most reliable one. But this relation was constant only for fixed contacts with arcrunners. For the moving contact, the mass loss ratio was a linear function of the effective value of the passing current.
|
|
|
DC arc extinguishing in low voltage switching devices for critical currents
Fencl, Martin ; Šimek, David (referee) ; Píška, Jakub (advisor)
This bachelor’s thesis deals with DC arc extinguishing for critical currents. The first, theoretical part describes and defines an arc, a DC arc and methods of its extinguishing. The second, theoretical part concerns spectral analysis – specifically, the emission method. Methods of research of extinguishing critical currents are also presented. The practical part consists of two measurements. The first measurement consists of spectrum measuring in time, in conjunction with voltage and current measurements. In the second measurement, the goal was to measure the dependence of arc burning time on voltage and current. The thesis concludes with summary of the results of each individual measurement and their presentation in the wider context.
|
|
|
Remanent magnetism of electromagnets of DC contactors
Horký, Jakub ; Píška, Jakub (referee) ; Šimek, David (advisor)
The master thesis is focused on a remanent magnetism of electromagnets of DC contactors. In the first part of the thesis deals with the formation of a magnetic field in different kinds of materials, description of their magnetization and sorting. The next part is focused on the principle and history of an electromagnet. Negative effects and remanent induction of the contactor are described in the end of the theoretical part. The second part is a practical part. First, the reaction times were measured on a pair of DC contactors. Using the obtained data, an electronic circuit was designed to minimize the difference in switching times of the given DC contactors.
|
|
|
Switching arc diagnostics in DC contactor
Píška, Jakub ; Kloc, Petr (referee) ; Valenta, Jiří (advisor)
Cílem této diplomové práce bylo provést diagnostiku vysokonapěťového stejnosměrného stykače se zaměřením na zpětnou komutaci a lepení oblouku, navrhnout a ověřit úpravy, které odstraní tyto negativní jevy. Měření obloukového napětí, tlaku a pomocí rychlokamery byly použity při diagnostice těchto jevů. Změny na arcrunnerech a jhu magnetického obvodu byly využity při jejich odstraňování. Úpravy na arcrunneru zmenšily skokové nárusty délky oblouku a úpravy na jhu navýšily sílu na oblouk mezi rozevírajícími se kontakty. Navrhnuté změny na stykači snížily časovou ztrátu v důsledku zpětné komutace, a tak zkrátily čas přenosu oblouku.
|
|
|
Contact erosion of switching devices
Píška, Jakub ; Šimek, David (referee) ; Valenta, Jiří (advisor)
This bachelor thesis deals with the erosion of contacts, as one of the negative phenomena affecting contacts of switchgears. In its first part, it briefly summarizes the other negative influences that must be considered when designing switching devices. In the following part, the physical mechanism of erosion and the primary criterion of assessment - weight loss are approached. The last and main part of the work deals with design of the contact system for comparing this loss for for frequently used materials and testing on a real switchgear. After the tests, the results were analyzed primarily from the perspective of ignition angles, the polarities of the current pulse and the current flowing through the arc. Taking into account the influence of the material composition, the size of the contacts and the presence of the arc-runner.
|
guest ::
