Sökning: "Rajeev Thottappillil"

Visar resultat 1 - 5 av 20 avhandlingar innehållade orden Rajeev Thottappillil.

1. 1. Interaction of Lightning Flashes with Wireless Communication Networks : Special Attention to Narrow Bipolar Pulses

   Författare :Mohd Riduan Ahmad; Vernon Cooray; Mahbubur Rahman; Rajeev Thottappillil; Uppsala universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; Latitude; Lightning; Narrow bipolar pulse; Wireless network.; Engineering Science with specialization in Atmospheric Discharges; Teknisk fysik med inriktning mot atmosfäriska urladdningar;

   Sammanfattning : In this thesis, the features of electric field signatures of narrow bipolar pulses (NBPs) generated by cloud flashes are investigated and their effects on wireless communication systems are studied. A handful amount of NBPs (14.5%) have been observed to occur as part of cloud-to-ground flashes in South Malaysia. LÄS MER

3. 2. On the Attachment of Lightning Flashes to Grounded Structures

   Författare :Marley Becerra; Vernon Cooray; Rajeev Thottappillil; Mats Boman; Ivo Gallimberti; Uppsala universitet; []
   Nyckelord :Engineering physics; Lightning; Lightning attachment; Positive leader discharges; Lightning protection; Thunderstorms; Numerical modeling; Teknisk fysik;

   Sammanfattning : This thesis deals with the physical modeling of the initiation and propagation of upward positive leader discharges from grounded structures during lightning strikes. It includes the analysis of upward leaders initiated under the influence of the electric field produced by a dominant negative cloud charge and due to the combined action of a negative thundercloud and a descending downward stepped negative leader. LÄS MER

4. 3. Magnetizing Currents in Power Transformers : Measurements, Simulations, and Diagnostic Methods

   Författare :Claes Carrander; Hans Edin; Göran Engdahl; Rajeev Thottappillil; Amr Adly; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Transformer core; diagnostics; three-phase; no-load; hysteresis; modeling; resonance; remanence; delta; Electrical Engineering; Elektro- och systemteknik;

   Sammanfattning : This thesis demonstrates a method for transformer core diagnostics. The method uses the no-load current of the transformer as an indicator, and gives different characteristic signatures for different types of faults or defects. Using the no-load current for the diagnostic gives high sensitivity. LÄS MER

5. 4. Electromagnetic noise generated in the electrified railway propulsion system

   Författare :Kelin Jia; Rajeev Thottappillil; Hans Bängtsson; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Electromagnetic compatibility; railway; propulsion system; shielded cable; transmission line; Electrical engineering; Elektroteknik; Telecommunication; Telekommunikation; SRA - Transport; SRA - Transport;

   Sammanfattning : The electromagnetic compatibility (EMC) problem in the railway propulsion system is a significant safety issue of high concern. The problems can be caused by any part of the propulsion system as well as any combination of the sub systems. Simulation is a fast economical way to understand the system and to predict the EMC performance. LÄS MER

7. 5. High Frequency Model of Electrified Railway Propulsion System for EMC Analysis

   Författare :Kelin Jia; Rajeev Thottappillil; Hans Bängtsson; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Electromagnetic compatibility; railway; propulsion system; multitransmission line; ac motor modeling; vector fitting; fast transient;

   Sammanfattning : A model of the electrified railway propulsion system working in a wide frequency range is studied in this thesis. The high frequency modeling is the first stage to study and predict the Electromagnetic compatibility (EMC) problems in the electrified railway propulsion system, which are safety and reliability issues of high concern. LÄS MER