DIELECTRICS AND ELECTRICAL INSULATION - DEI.pdf · • Gian Carlo Montanari, University of Bologna...
Transcript of DIELECTRICS AND ELECTRICAL INSULATION - DEI.pdf · • Gian Carlo Montanari, University of Bologna...
DIELECTRICS AND ELECTRICAL INSULATION Robert Hebner, Ph.D. Center for Electromechanics University of Texas at Austin
Background - Personal • Decades of research experience • 50+ publications in the field • Twice selected president of the IEEE Dielectrics and
Electrical Insulation Society
Simulating Mode Transitions during Breakdown in Liquids Brian T. Murphy, Robert E. Hebner, Edward F. Kelley
Longer free path
Background - CEM
Stress Grading
A. Roberts, Electrical Insulation Magazine, 1995
Semiconductive Coating
Stress Grading Coating
Endwinding Insulation
Copper Conductors
Two conference papers
Forensic investigation Failure due to rubbing and flow
(Okabe, et al. IEEE Trans. Diel. Elec. Insulation, 2006)
Basic materials properties
Experience in application environment*
Electrical environment*
*CEM Focus
VG 12968k
Key Takeaways Vendor knows material – user knows environment
Failures are due to environment
Published NAVAIR Data on Wiring Failure
5
Chafed wire insulation leading to short circuit and/or arcing 37%
Short circuit, unspecified cause (includes arcing incidents)18%
Broken wires11%
Connector failure 9%
Unspecified failure 6%
Failure due to corrosion 5%
Loose connection 4%
Insulation failure
3%
Circuit breaker failure 2%
Crossmating 2%
Short due to corrosion 1%
Miswire 1%
Other 1%
Failure primarily due to environment, not poor insulation
Current CEM Research - Cables • Cable plant is too large in electrified
• Ships • Aircraft • Automobiles
• Analysis for existing and emerging materials is that they can be significantly smaller thermally and electrically.
• Focus is developing environmental tests that predict life. • Multiphysics challenge
• Electrical • Thermal • Mechanical • Chemical
Technical Approach • Focus on dc cables
• Much less physics-of-failure data for dc • Worldwide interest growing
• Cable plant can be smaller if loads are also dc
• Accelerate electrical/mechanical/thermal aging
• Use partial discharge measurements to gauge health
PD initiated
Space charge impact after polarity reversal – a unique dc
challenge
Strategic Partnership • Gian Carlo Montanari, University of Bologna
• Globally recognized expert in relating partial discharge to life • Partnership mired in legal issues at present, but expect success
• Access to EU-funded program data and materials • Joint paper
• Trying to explore a Bayesian, rather than strictly measurements based approach, to life estimation.
Anticipated Next Focus • Wide Band Gap semiconductors
enable higher voltage operation. • Packaging problems occurring
• Partial discharges • Surface discharges • EMI • Thermal failure
• CEM, ME, ECE collaborative research
Polyimide Damage
Temperature measurement using UT’s thermal imaging microscope system
Needed R&D • 3-d, multiphysics model
of semiconductor package
• Integrated cooling • Functionally graded
materials • Possibly via additive
package manufacturing
EW-enhanced heat pipe evaporator
EW voltage
Heat flux
Nucleate boiling
EW-‐enhanced evaporator Higher heat transfer via EW-‐stabilized nucleate
boiling (dryout prevention)
Heat transfer mechanism: Nucleate boiling
Heat pipe evaporator
Heat flux
Evaporation
Traditional heat pipe evaporator
Heat transfer mechanism: Conduction & evaporation
Conduction
Hot surface
Vapor layer Liquid
Proximity electrode
Surface dryout Hot surface
Liquid 100 V applied
Dryout preven=on (sustained nucleate boiling)
Demonstra*on of nucleate boiling and dryout preven*on using electrowe8ng (EW)
Summary • UT research aims
• Improved asset management via better life prediction • Characterizing use environment
• Modeling and manufacturing technologies that lead to longer service life
• Team with others for access to emerging materials