Sökning: "medium frequency"

Visar resultat 1 - 5 av 197 avhandlingar innehållade orden medium frequency.

1. 1. A Novel Oil-immersed Medium Frequency Transformer for Offshore HVDC Wind Farms

   Författare :Mohammad Kharezy; Per Olof Hedekvist; Yuriu Serdyuk; Thomas Hammarström; Karsten Backhaus; RISE; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; prototype design methodology; finite element analysis; HVDC insulation design; medium frequency transformer; Wind energy; DC-DC power converters;

   Sammanfattning : In this project, a design of an oil type medium frequency transformer for offshore wind farm applications is proposed. The design is intended for applications when series coupling of the output of the DC/DC converters of the wind turbine on their secondary side is done to achieve a cost-effective high voltage solution for collecting energy from offshore wind parks. LÄS MER

3. 2. On the Dielectric Losses of Polyethylene at Medium and High Frequencies

   Författare :Martin Strååt; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Dielectric properties; foaming; crystallinity; polyethylene; frequency; porosity;

   Sammanfattning : AbstractAs mobile communication moves from 3G to 4G, the bandwidth used will be extended from 2 GHz to 5 GHz. The propagation loss is related to the 2.6:th power of frequency, thus a large increase in power consumption may be expected. LÄS MER

4. 3. Time-Frequency Analysis in Attosecond Spectroscopy

   Författare :Marcus Isinger; Atomfysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Attosecond; Spectroscopy; Time-Frequency; High-order harmonic generation; Rabitt; Interferometry;

   Sammanfattning : This thesis deals with ultrafast dynamics of electronic processes in rare gas atoms. The processes we explore include photoemission, where we time the emission of electrons moving away from the atomic core following ionization by a photon; and auto-ionization, where the atom spontaneously releases an electron wave-packet following photo-excitation. LÄS MER

5. 4. High Frequency Tyre Vibrations

   Författare :Patrik Andersson; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; local deformation; adhesion; tyre model; air pumping; parameter study; tyre road noise; tyre road prediction models; tyre noise;

   Sammanfattning : High frequency (above 1 kHz) noise generation from the tyre/road interaction is still not fully understood and accurately modelled.Two noise generation mechanisms previously suggested in the literature are reviewed: air pumping and noise generation cased by adhesive effects between the tyre tread and road surface. LÄS MER

7. 5. Design and Optimization Considerations of Medium-Frequency Power Transformers in High-Power DC-DC Applications

   Författare :Amin Bahmani; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Nanocrystalline-Magnetic Core; High-Power Isolated DC-DC Converter; Solid-State Transformers; Leakage Inductance; Isolation Requirements; Medium-Frequency Power Transformer;

   Sammanfattning : Recently, power electronic converters are considered as one of the enabling technologies that can address many technical challenges in future power grids from the generation phase to the transmission and consequently distribution at different voltage levels. In contrast to the medium-power converters (5 to 100 kW) which have beenessentially investigated by the automotive and traction applications, megawatt and medium-voltage range isolated converters with a several kilohertz isolation stage,also called solid-state transformers (SST), are still in an expansive research phase. LÄS MER