Method for the Prediction of the Potential Distribution in Electrical Machine Windings under Pulse Voltage Stress

2020 ◽  
pp. 1-1
Author(s):  
Alexander Hoffmann ◽  
Bernd Ponick
Keyword(s):  
Potential Distribution ◽  
Pulse Voltage ◽  
Electrical Machine ◽  
Voltage Stress

scholarly journals Method to Predict the Non-Uniform Potential Distribution in Random Electrical Machine Windings under Pulse Voltage Stress

Energies ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 358
Author(s):  
Alexander Hoffmann ◽  
Bernd Ponick
Keyword(s):  
Equivalent Circuit ◽  
Potential Distribution ◽  
Solution Process ◽  
Practical Method ◽  
Electrical Machine ◽  
Stator Core ◽  
Design Data ◽  
Potential Oscillations ◽  
Voltage Stress ◽  
The Time Domain

This article describes a practical method for predicting the distribution of electric potential inside an electrical machine’s winding based on design data. It broadens the understanding of winding impedance in terms of inter-winding behavior and allows to properly design an electrical machine’s insulation system during the development phase. The predictions are made based on an frequency-dependent equivalent circuit of the electrical machine which is validated by measurements in the time domain and the frequency domain. Element parameters for the equivalent circuit are derived from two-dimensional field simulations. The results demonstrate a non-uniform potential distribution and demonstrate that the potential difference between individual turns and between turns and the stator core exceeds the expected values. The findings also show a link between winding impedance and potential oscillations inside the winding. Additionally, the article provides an overview of the chronological progression of turn-based models and shows how asynchronous multiprocessing is used to accelerate the solution process of the equivalent circuit.

scholarly journals Endurance of Polymeric Insulation Foil Exposed to DC-Biased Medium-Frequency Rectangular Pulse Voltage Stress

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 13 ◽  
Author(s):  
Raphael Färber ◽  
Thomas Guillod ◽  
Florian Krismer ◽  
Johann Kolar ◽  
Christian Franck
Keyword(s):  
Risk Factors ◽  
Degradation Process ◽  
Rectangular Pulse ◽  
Pulse Voltage ◽  
Switching Frequency ◽  
Time To Failure ◽  
Medium Frequency ◽  
Pulse Modulation ◽  
Peak Voltage ◽  
Voltage Stress

The endurance of polymeric insulation foil is investigated under a mixed medium-voltage stress (DC + medium-frequency rectangular pulse) by means of accelerated lifetime testing. A dedicated setup is used that allows us to selectively eliminate the known risk factors for premature insulation failure under medium-frequency pulse voltage stress: partial discharges (PDs) during pulse transitions, excessive dielectric heating, and systemic overvoltages. The obtained results on polyethylenterephtalat (PET) insulation foil suggest that the adequate consideration of these factors is sufficient for eliminating the adverse effects of the pulse modulation under the investigated conditions. Indeed, if all mentioned risk factors are eliminated, the time to failure observed under a pure DC stress is shorter than with a superimposed pulse (keeping the same peak voltage). There is then no indication of an additional detrimental “per pulse” degradation process (i.e., the time to failure is not dependent on pulse frequency). In contrast, when repetitive PDs are present, the lifetime under combined DC + rectangular pulse stress strongly decreases with increasing pulse switching frequency. PD erosion of the foil is quantified by means of confocal microscopy, and the applicability of the streamer criterion for predicting PD inception is discussed.

The effects of surface absorbed monolayer microdiffraction patterns

1988 ◽  
Vol 46 ◽  
pp. 680-681
Author(s):  
M. Pan ◽  
J.M. Cowley
Keyword(s):  
Surface Potential ◽  
Electron Probe ◽  
Potential Distribution ◽  
Crystal Surface ◽  
Normal Direction ◽  
Surface Image ◽  
Extended Surface ◽  
Gas Molecules ◽  
Surface Nature ◽  
Electron Microdiffraction

Electron microdiffraction patterns, obtained when a small electron probe with diameter of 10-15 Å is directed to run parallel to and outside a flat crystal surface, are sensitive to the surface nature of the crystals. Dynamical diffraction calculations have shown that most of the experimental observations for a flat (100) face of a MgO crystal, such as the streaking of the central spot in the surface normal direction and (100)-type forbidden reflections etc., could be explained satisfactorily by assuming a modified image potential field outside the crystal surface. However the origin of this extended surface potential remains uncertain. A theoretical analysis by Howie et al suggests that the surface image potential should have a form different from above-mentioned image potential and also be smaller by several orders of magnitude. Nevertheless the surface potential distribution may in practice be modified in various ways, such as by the adsorption of a monolayer of gas molecules.

New Holtz Electrical Machine

1877 ◽  
Vol 3 (70supp) ◽  
pp. 1108-1108
Author(s):  
Elihu Thomson
Keyword(s):  
Electrical Machine
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