DIELECTRICS AND ELECTRICAL INSULATION. Robert Hebner, Ph.D. Center for Electromechanics University of Texas at Austin

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1 DIELECTRICS AND ELECTRICAL INSULATION Robert Hebner, Ph.D. Center for Electromechanics University of Texas at Austin

2 Background - Personal Decades of research experience 50+ publications in the field Twice selected president of the IEEE Dielectrics and Electrical Insulation Society Longer free path Simulating Mode Transitions during Breakdown in Liquids Brian T. Murphy, Robert E. Hebner, Edward F. Kelley

3 Background - CEM Stress Grading Semiconductive Coating Two conference papers Stress Grading Coating Endwinding Insulation A. Roberts, Electrical Insulation Magazine, 1995 Copper Conductors Forensic investigation Failure due to rubbing and flow

4 VG 12968k Key Takeaways Vendor knows material user knows environment Failures are due to environment (Okabe, et al. IEEE Trans. Diel. Elec. Insulation, 2006) Basic materials properties Experience in application environment* Electrical environment* *CEM Focus

5 Published NAVAIR Data on Wiring Failure Chafed wire insulation leading to short circuit and/or arcing 37% Short circuit, unspecified cause (includes arcing incidents) 18% Broken wires 11% Connector failure 9% Other 1% Miswire 1% Short due to corrosion 1% Crossmating 2% Insulation failure 3% Circuit breaker failure 2% Unspecified failure 6% Failure due to corrosion 5% Loose connection 4% 5 Failure primarily due to environment, not poor insulation

6 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

7 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 Space charge impact after polarity reversal a unique dc challenge PD initiated

8 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.

9 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

10 Needed R&D 3-d, multiphysics model of semiconductor package Integrated cooling Functionally graded materials Possibly via additive package manufacturing Heat transfer mechanism: Conduction & evaporation Evaporation Heat transfer mechanism: Nucleate boiling Nucleate boiling EW voltage Conduction Heat pipe evaporator EW-enhanced heat pipe evaporator Heat flux Traditional heat pipe evaporator Proximity electrode Liquid Heat flux EW- enhanced evaporator Higher heat transfer via EW- stabilized nucleate boiling (dryout prevention) 100 V applied Liquid Vapor layer Hot surface Surface dryout Hot surface Dryout preven=on (sustained nucleate boiling) Demonstra*on of nucleate boiling and dryout preven*on using electrowe8ng (EW)

11 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