Partial Discharge Measurements on Dibenzyltoluene for High Temperature Encapsulant Application up to 350°C

Ghassemi

IEEE Trans. Dielect. Electr. Insul.

2021

This manuscript critically reviews recent research on electrical insulation materials and systems used in power electronics devices and focuses on electrical treeing in silicone gel, PD modeling, and mitigation methods. For mitigation methods, electric field grading techniques, such as 1) various geometrical techniques, and 2) applying nonlinear dielectrics are discussed. Alternatives for silicone gel, such as liquid dielectrics, are also highlighted. The drawbacks of reported research and technical gaps are identified. In particular, we show that the investigations carried out to date are in their infancy regarding the working conditions targeted for next-generation WBG power devices. This review will provide a useful framework and point of reference for future research.

Section: Mitigation Methodsmentioning

confidence: 99%

Section: Mitigation Methodsmentioning

confidence: 99%

Section: Mitigation Methodsmentioning

confidence: 99%

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Insulation Materials and Systems for Power Electronics Modules: A Review Identifying Challenges and Future Research Needs

Ghassemi

IEEE Trans. Dielect. Electr. Insul.

2021

2022 IEEE 4th International Conference on Dielectrics (ICD)

“…PDs in silicone gel quickly reduce its insulation capabilities due to formation of permanent cavities [1][2][3]. PD measurements carried out with liquids instead of gel [4] evidenced the fact that embedding substrates in a high temperature liquid such as JarythermDBT provides good PD properties at high temperatures, up to 350°C with Alumina substrates, i.e., far higher than the maximum temperature limit of silicone gels.…”

Section: Introductionmentioning

confidence: 99%

Breakdown Properties of Epoxy and Ceramic Substrates Embedded in Liquids at High Temperature

Muslim

Lesaint

Hanna

et al. 2022

Surface breakdown is investigated with substrates made either from standard glass/epoxy PCB board or Alumina ceramic, and embedded in silicone gel or dibenzyltoluene (DBT) high temperature liquid. Depending on the substrate nature and gap distance, breakdown may occur either above the surface within the encapsulant material, or below within the solid substrate. In the case of ceramic substrate with liquid encapsulation, which could be tentatively used at high temperatures above 200°C, the weakest material is the ceramic, which shows irreversible degradation (cracks) after a single breakdown. Therefore, such insulating structure does not benefit from the self-healing character of liquids. Breakdown voltages also show a marked decrease at high temperature.

“…Silicone gel is used for encapsulation to prevent in situ electrical discharges in air and to protect substrates, semiconductors and connections against humidity, dirt and vibration. Although alternatives have been researched [6][7][8], silicone gel, which is a weaker insulator than dielectric ceramics and more vulnerable to PDs, is still the only option for encapsulation of WBG power modules. A thorough and in-depth review of PD measurements, failure analyses and control in high-power Si-Insulated-gate bipolar transistor (IGBT) modules has been done in [9,10].…”

Section: Introductionmentioning

confidence: 99%

A Finite Element Analysis Model for Partial Discharges in Silicone Gel under a High Slew Rate, High-Frequency Square Wave Voltage in Low-Pressure Conditions

Borghei

Ghassemi

2020

Energies

Wide bandgap (WBG) devices made from materials such as SiC, GaN, Ga2O3 and diamond, which can tolerate higher voltages and currents compared to silicon-based devices, are the most promising approach for reducing the size and weight of power management and conversion systems. Silicone gel, which is the existing commercial option for encapsulation of power modules, is susceptible to partial discharges (PDs). PDs often occur in air-filled cavities located in high electric field regions around the sharp edges of metallization in the gel. This study focuses on the modeling of PD phenomenon in an air filled-cavity in silicone gel for the combination of (1) a fast, high-frequency square wave voltage and (2) low-pressure conditions. The low-pressure condition is common in the aviation industry where pressure can go as low as 4 psi. To integrate the pressure impact into PD model, in the first place, the model parameters are adjusted with the experimental results reported in the literature and in the second place, the dependencies of various PD characteristics such as dielectric constant and inception electric field on pressure are examined. Finally, the reflections of these changes in PD intensity, duration and inception time are investigated. The results imply that the low pressure at high altitudes can considerably affect the PD inception and extinction criterion, also the transient state conditions during PD events. These changes result in the prolongation of PD events and more intense ones. As the PD model is strongly dependent upon the accurate estimation electric field estimation of the system, a finite-element analysis (FEA) model developed in COMSOL Multiphysics linked with MATLAB is employed that numerically calculates the electric field distribution.