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The most important stress factors for electric machines insulation in the automotive environment can be summarized by the mnemonic expression TEAM (thermal, electrical, ambient, and mechanical stress). Even already each individual of the above mentioned stresses can be fatal for the electric machine insulation they generally act simultaneously making even worse deterioration process and so faster...
Thermal interface materials (TIMs) are an important enabler for low thermal resistance and reliable electronics packaging for a wide array of applications. There is a trend towards bonded interface materials (BIMs) because of their potential for low thermal resistance (<1 mm2-K/W). However, due to coefficient of thermal expansion mismatches between various layers of a package, thermomechanical...
Despite recent advancements in material technology, oil-cellulose insulation systems in form of so called Transformerboard combined with paper and mineral oil are still one of the backbones of high voltage technology. This insulation system is widely used in the high voltage industry, especially in high voltage transformers for AC and HVDC applications, e.g. converter transformers. The space charge...
The indentation-induced shape-memory behavior in both an aged and a solutionized austenitic nickel-titanium (NiTi) alloy was investigated by Vickers indentation. The depth recovery ratio of the indents as well as the formation of protrusions on the surface after planarization was analyzed after the sample was heated above and cooled below the phase transformation temperature using a white light interferometer...
In the context of improving high voltage equipment recyclability, thermoplastic polymers like polyethylene terephtalate (PET) have become attractive candidates for replacing non-recyclable (thermosetting) insulators. In order to assess the suitability of PET for high voltage applications, its behavior under long term thermo-electrical ac stress has been investigated in the present work. Evolutions...
Radial field, medium voltage cables operated at 6.6 kV are the object of this study. Dielectric properties of those aged PVC insulated cables have been measured as a function of temperature and voltage in a frequency range of 1 mHz to 1 kHz. The range of temperature tested was between 30°C to 110°. The dielectric material shows a resistive behavior at low frequency. Deduced conductivities are in good...
Each electrical insulating material or system in large electric machines is precisely designed and later monitored in operation. The task for monitoring the state of the machine is information about rest life time of such as machine. The key element of electrical machine is its electroinsulating system. For proper rest life time calculation of an insulation system it is necessary to have complete...
For the maintenance of electric power systems a fundamental focus is to monitor the efficiency of components of a distribution system. For the electrical distribution circuits the paper suggests a Maintenance Tool based on the evaluation of the insulated cables deterioration. To do it off line, the author deals a practical and useful Cable Maintenance Tool “MCT”, evaluating a check up of the cable...
Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high-strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to leadfree solders has resulted...
Electrical technology diagnostics is a branch of science examining the actual state of electrical machinery under the operation when using two basic accesses. The first and older one is an “off-line diagnostics”. It means a device or an appliance subjected to diagnostic process need to be for example disconnected from circuit, turned off or stopped. An on-line diagnostics — diagnosing a device during...
The stator wedge supporting material is used for diagnosing the state of the main insulation in rotating machines. The stator wedge is placed in a stator slot, and the material is aged using the same degradation conditions experienced by the bar winding insulating system itself. The possibility of easy replacement of the supporting material without causing any damage to the whole insulating system...
High junction temperature accelerates the degradation of the chips and the package materials of high power light emitting diodes (LEDs). In this paper, two experiments were conducted to investigate the fluctuation of junction temperature in the aging process. At the ambient temperature of 65°C, the samples from four different types of LED packages were used to investigate the variation of junction...
A fully enclosed oil circulation rig has been made for studying the temperature-dependent equilibrium distribution of contaminants between oil-impregnated cellulose materials and oil. This is relevant for the distribution of contaminants in the solid insulation in power transformers. Used with clean, new material the rig gave humidity equilibrium results reasonably close to results found in literature...
This paper presents new investigations on the aging of Thermal Interface Materials (TIM) subjected to thermal cycling conditions. The challenge was to design a specific and original set-up in order to not only undergo avionic temperature mission profile (−50°C/+150°C) but also to perform standardized thermal characterization at always same conditions. Thermal conductivity is used as aging indicator...
During their operating service, insulated power cables can be exposed to wet environment. The presence of moisture in cables surroundings may affect the properties of the used insulation material for instance, XLPE widely employed in MV and HV power cables insulation and therefore the reliability of the insulated cables. In order to examine the influence of wet aging conditions on the performances...
To ensure high reliability for advanced automotive electronics, investigation and understanding on the failure mechanisms under harsh conditions are needed. New methods and technologies for improved reliability and increased lifetime should be developed. In this paper, an investigation on the effect of high temperature aging on the thermomechanical properties, microstructure of the molding compounds...
In this paper the effect on dc and ac electrical properties of silica nano and micro particles dispersed in epoxy resins is discussed. In particular, space charge, conductivity, dielectric strength and partial discharge resistance is analyzed. The results show that nanostructured materials exhibit smaller space charge accumulation with respect to both base and microfilled materials. Regarding PD resistance,...
Heat dissipation for packaging high-power light-emitting diodes is critically important to performance and reliability of LED lighting modules. The first thermal interface encountered by the heat flow is a die-attach material between the diode chip and its substrate. In this study, three different types of die-attach materials were used to construct 1-Watt GaN LED single-chip modules: a silver epoxy...
The typical approach to investigate the reliability of plastic packages is based on material characterizations. Thereby the material characterization is carried out using standard methods like Dynamic Mechanical Analysis (DMA) and Thermo-Mechanical Analysis (TMA). Based on these results the change of Epoxy Moulding Compounds (EMC) thermo-mechanical properties is used to predict long-term stress changes...
The working life of electrical machines is primary affected by the insulation system quality. Diagnostics methods help to understand the momentary state of insulation and to avoid the possible damage or electrical breakdown of machines through the repair or insulation rewinding. Partial discharges testing belongs to one of the high applicable test method of insulating materials within electrical machines...
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