The Effect of Water Absorption in Ceramic Coatings on High Frequency ac Resistance

2021 ◽  
Author(s):  
K. Bobzin ◽  
W. Wietheger ◽  
E. Burbaum
Keyword(s):  
Water Absorption ◽  
High Frequency ◽  
Ceramic Coatings ◽  
Electrical Insulation ◽  
Wear Protection ◽  
Frequency Regime ◽  
Porous Microstructure ◽  
High Frequency Ac ◽  
Steel Substrates ◽  
Thermally Sprayed

Abstract Thermally sprayed ceramic coatings can be used for wear protection as well as thermal and electrical insulation. When exposed to environments with high humidity, the water absorption of the ceramic coating has a tremendous impact on the electrical insulation. In thermally sprayed ceramic coatings, water can easily be absorbed by the porous microstructure of the coating. A general result of the water absorption is the reduction of the dc resistivity. However, in the high frequency regime of ac loads, contrary results were observed for sealed Al2O3 coatings on steel substrates. Specimens exposed to high air humidity have shown an increased ac resistance compared to dry specimens if frequencies above 1 MHz are considered. To analyse this phenomenon, a novel measurement technique was developed to investigate the influence of the water absorption of detached ceramic coatings on the ac resistivity at high frequencies. Moreover, the water absorption of the ceramic is measured gravimetrically. To ensure the results are also applicable to ceramic coatings on substrates, the morphology of the coating was analysed using electron microscopy and compared to reference specimens deposited on steel substrates from [1].

Resonant BLDC Motor Drive System for Medical Applications

2019 ◽  
Vol 14 ◽  
Author(s):  
C. Vidhya ◽  
V. Ravikumar ◽  
S. Muralidha
Keyword(s):  
High Frequency ◽  
Pulse Width Modulation ◽  
Power Converter ◽  
Low Power Consumption ◽  
Motor Drive ◽  
Medical Applications ◽  
Bldc Motor ◽  
Three Phase ◽  
High Frequency Ac ◽  
Motor Drive System

: The objective of this paper is to implement an ac link universal power converter controlled BLDC motor for medical applications. The ac link universal power converter is a soft switched high frequency ac link converter, created using the parallel combination of an inductor and a capacitor. The parallel ac link converter handle the ac voltages and currents with low reactive ratings at the link and offers improved power factor, low power consumption, more efficiency and less weight on comparison with the traditional dc link converter. Because of the high throughput, BLDC motors are preferred widely medical applications. A modulation technique called Space Vector Pulse Width Modulation (SVPWM) is used to generate the three phase power for the BLDC motors from the input DC supply. To validate the proposed system, simulations are performed in MATLAB – Simulink and an experimental prototype is constructed to supplement the simulation results.

Advanced High Frequency AC Microgrid with integrated power quality conditioning capability

2009 ◽  
Author(s):  
Fredi Z. Ferrigolo ◽  
Diego B. Ramos ◽  
Jeferson M. Correa ◽  
Felix A. Farret ◽  
Luciano P. Lima
Keyword(s):  
Power Quality ◽  
High Frequency ◽  
High Frequency Ac ◽  
Ac Microgrid

Laser Sintering of Nano-Al2O3 Powders on Plasma Sprayed Ceramic Based Coatings

2007 ◽  
Author(s):  
Lida Shen ◽  
Yinhui Huang ◽  
Zongjun Tian ◽  
Guoran Hua
Keyword(s):  
Wear Resistance ◽  
Corrosion Resistance ◽  
Plasma Spraying ◽  
Bond Coat ◽  
Continuous Wave ◽  
Ceramic Coatings ◽  
Laser Sintering ◽  
Al2o3 Ceramic ◽  
Plasma Sprayed ◽  
Steel Substrates

This paper describes an investigation of nano-Al2O3 powders reinforced ceramic coatings, which has included NiCrAl and Al2O3+13%wt.TiO2 coats pre-produced by atmosphere plasma spraying, implemented by laser sintering. Commercial NiCrAl powders were plasma sprayed onto 45 Steel substrates to give a bond coat with thickness of ∼100μm. The 600μm thick Al2O3+13%wt.TiO2 based coating was also plasma sprayed on top of the NiCrAl bond coat. With 2.5kw continuous wave CO2 laser, nano-Al2O3 ceramic powders were laser sintered on the based Coatings. The micro structure and chemical composition of the modified Al2O3+13%wt.TiO2 coatings were analyzed by such detection devices as scanning electronic microscope (SEM) and x-ray diffraction (XRD). Microhardness, wear resistance and corrosion resistance of the modified coatings were also tested and compared with that of the unmodified. The results show that the crystal grain size of Al2O3 had no obvious growth. In addition, due to the nanostructured Al2O3 ceramic phases, the coatings exhibited higher microhardness, better wear resistance and corrosion resistance than those unmodified counterparts. The complex process of plasma spraying with laser sintering as a potential effective way of the application of ceramic nano materials was also simply discussed and summarized in the end.

Time-resolved magneto-optical imaging of Y1Ba2Cu3O7−δthin films in high-frequency AC current regime

2006 ◽  
Vol 19 (6) ◽  
pp. 667-670 ◽  
Author(s):  
A Lucarelli ◽  
G Lüpke ◽  
T J Haugan ◽  
G A Levin ◽  
P N Barnes
Keyword(s):  
Optical Imaging ◽  
High Frequency ◽  
Time Resolved ◽  
Current Regime ◽  
Ac Current ◽  
High Frequency Ac

scholarly journals A comparison of coarse spaces for Helmholtz problems in the high frequency regime

2021 ◽  
Vol 98 ◽  
pp. 239-253
Author(s):  
Niall Bootland ◽  
Victorita Dolean ◽  
Pierre Jolivet ◽  
Pierre-Henri Tournier
Keyword(s):  
High Frequency ◽  
Frequency Regime

The Effect of HFPD Thermally Sprayed WC-Co Coatings on the Fatigue Behavior and Deformation of Al 2024-T4

2000 ◽  
Author(s):  
A. Ibrahim ◽  
C.C. Berndt
Keyword(s):  
High Frequency ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Pulse Detonation ◽  
Deformation Behaviors ◽  
Life Distributions ◽  
Thermally Sprayed ◽  
Al 2024 ◽  
Frequency Pulse

Abstract The effect of high frequency pulse detonation (HFPD) and HVOF thermally sprayed WC-Co coatings on the high cycle fatigue (HCF) behavior of 2024-T4 aluminum was investigated. The fatigue life distributions of specimens in the polished and coated conditions are presented as a function of the probability of failure. The monotonic and cyclic deformation behaviors of the as-received and as-coated specimens were investigated. The conclusions show that, (i) the HFPD sprayed specimens exhibited slightly higher fatigue lives compared to the uncoated specimens, (ii) the HVOF sprayed specimens exhibited significantly higher fatigue lives compared to the uncoated specimens, and (iii) the as-coated specimen was cyclically stable.

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