Sökning: "square-like voltages"

Hittade 5 avhandlingar innehållade orden square-like voltages.

1. 1. Partial Discharges at Fast Rising Voltages

   Författare :Thomas Hammarström; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; short rise time; cavities; high dV dt.; measurements; Partial discharges; square like voltages; repetitive voltages;

   Sammanfattning : The present demand for higher efficiency and flexibility in the energy sector has led to an increased use of power electronic generated waveforms as these allow energy conversion between different frequencies including DC. The generated waveforms are usually synthesized by so called Pulse Width Modulation (PWM) techniques, where the desired waveform is approximated by a number of square shaped pulses with a short rise time. LÄS MER

3. 2. Partial Discharges at Repetitive Rapidly Changing Voltages

   Författare :Elisabeth Lindell; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; high dV dt; oil paper insulation.; repetitive voltages; short rise time; partial discharge measuring techniques; twisted pair; square-like voltages; corona; Partial discharges PDs ;

   Sammanfattning : Electrical insulation can today be exposed to voltages having considerably higherfrequency components than the conventional power frequency AC 50 Hz or 60 Hz,for example due to the increased use of power electronics in power systems. Thishas in a number of cases caused unexpected behaviour, including failures. LÄS MER

4. 3. Detection of Partial Discharges at Fast Rising Voltages

   Författare :Thomas Hammarström; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Partial discharges; cavities; repetitive voltages; high dV dt.; square like voltages; short rise time; measurements;

   Sammanfattning : The present demand for higher efficiency and flexibility in the energy sector has ledto an increased use of power electronic generated waveforms as these allow energyconversion between different frequencies including DC. The generated waveformsare usually synthesized by so called Pulse Width Modulation (PWM) techniques,where the desired waveform is approximated by a number of square shaped pulseswith a short rise time. LÄS MER

5. 4. Measurement and Analysis of Partial Discharges at Semi-Square Voltages

   Författare :Elisabeth Lindell; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; space charge; Partial discharges PDs ; short rise time; partial discharge measuring techniques; square-like voltages; repetitive voltages; corona;

   Sammanfattning : Insulation is today being exposed to voltages having considerably higher frequency components than the conventional power frequency AC 50 Hz or 60 Hz, for example in motors supplied by adjustable speed drives based on pulse width modulated converters. This has in many cases caused unexpected behaviour of the insulation systems. LÄS MER

7. 5. Characterization of Electrical Insulation Exposed to Arbitrary Voltage Waveforms

   Författare :Björn Sonerud; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; arbitrary voltage waveforms; partial discharge; diagnostics; dielectric response measurement; signal processing; electrical treeing; dielectric heating.;

   Sammanfattning : The extensive use of power electronics in power systems today gives rise to other voltage waveforms than the conventional 50/60 Hz sinusoidal and consequently other types of electric stress act on high voltage insulating materials. Previous studies has shown that Pulse Width Modulated (PWM) voltages and similar waveforms increase stress in Adjustable Speed Drives (ASD) as compared with sinusoidal waveforms and it has also been shown that partial discharge (PD) activity is intensified during PWM voltages and that rise time of square like pulses affect PD inception voltage. LÄS MER