Search for dissertations about: "electrical discharge"
Showing result 1 - 5 of 134 swedish dissertations containing the words electrical discharge.
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1. Numerical Simulations of Long Spark and Lightning Attachment
Abstract : 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. READ MORE
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2. Physics of Electrical Discharge Transitions in Air
Abstract : 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. READ MORE
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3. Electrical Characterisations of Bearings
Abstract : 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. READ MORE
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4. Electrical Characterization of Partial Discharge Resistant Enamel Insulation
Abstract : 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. READ MORE
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5. Characterization of Electrical Insulation Exposed to Arbitrary Voltage Waveforms
Abstract : 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. READ MORE