Sökning: "electrical discharge"

Visar resultat 1 - 5 av 134 avhandlingar innehållade orden electrical discharge.

  1. 1. Numerical Simulations of Long Spark and Lightning Attachment

    Författare :Liliana Arevalo; Vernon Cooray; Dan Windmar; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; breakdown; discharge; leader channel; lightning attachment; negative discharge; positive discharge; streamer; Electrical engineering; Elektroteknik; Engineering Science with specialization in Atmospheric Discharges; Teknisk fysik med inriktning mot atmosfäriska urladdningar;

    Sammanfattning : The research work presented here is concerned with numerical simulations of two different electrical phenomena: Long gap electrical discharges under switching impulses and the lightning attachment process associated with positive upward leaders. The development of positive upward leaders and the progression of discharges in long gaps are attributable to two intertwined physical phenomena, namely, the leader channel and the streamer zone. LÄS MER

  3. 2. Physics of Electrical Discharge Transitions in Air

    Författare :Lipeng Liu; Marley Becerra; Ute Ebert; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; electrical discharges; transition; streamers; glow corona; leader discharges; elektriska urladdningar; övergång; streamers; glöd-korona; ledarurladdningar; Electrical Engineering; Elektro- och systemteknik;

    Sammanfattning : Electrical discharges with a variety of different forms (streamers, glow corona, leaders, etc.) broadly exist in nature and in industrial applications. Under certain conditions, one electrical discharge can be transformed into another form. LÄS MER

  4. 3. Electrical Characterisations of Bearings

    Författare :Abhishek Joshi; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Ball bearing; Equivalent circuit model; Lubricants; Bearing Capacitance; Spherical bearing; Mechanical bearing; Bearing currents; Electrical conduction; Electrical characterisation;

    Sammanfattning : Mechanical bearings are an integral part of industry, and are used in various places in order to reduce friction between two interacting surfaces and are used to transmit power and loads. Mechanical bearings are one of the most extensively used components within the wind industry, but on the other hand they are also one of the most dominantly failing failed components. LÄS MER

  5. 4. Electrical Characterization of Partial Discharge Resistant Enamel Insulation

    Författare :Tuan Anh Hoang; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Enamel wire insulation; dipolar polarization; charge injection; charge transport; chromium oxide; dc conductivity; partial discharge; twisted pair.; dielectric permittivity;

    Sammanfattning : Adjustable speed drives for rotating machines have become increasingly popular as they provide possibilities of smooth and accurate process control as well as for energy savings. In such systems, due to the fact that the voltage applied at terminals of motor windings is no longer purely sinusoidal but characterized by a high content of harmonics, the appearing electrical and thermal stresses yield premature failures of the winding insulation, mainly because of an increased partial discharge (PD) activity. 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