Performance Degradation Model and Reliability Evaluation of Brush DC Motor for the Intelligent on–Off Valve

Yang Tianhao,Li Shanhu,Duan Shuyong,Tao Yourui,Han Xu 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3

Application of the intelligent on–off valve reduces heat loss. As the critical control component of the intelligent on–off valve, the health state of the brush DC motor directly impacts whether the intelligent on–off valve can perform the regular operation. Therefore, the reliability evaluation of the brush DC motor is of great significance to the whole heat supply network. In this study, the failure mechanism of the brush DC motor is analyzed, and the absolute value of steady-state current variation is taken as the performance degradation characteristic parameter. According to the performance degradation characteristic parameter, the performance degradation model based on the Wiener process is established, and the inverse power rate acceleration model is introduced into the Wiener process to derive the reliability function of the motor. Based on the actual operating conditions that the motor in the intelligent on–off valve needs to start and stop frequently, an accelerated life test based on start-stop is designed. The error analysis result shows that the error between the expected start-stop times predicted by the proposed and the actual average failure start-stop times is only 2.14%. The proposed degradation model is more accurate than the motor's traditional performance degradation model.

A Deep Investigation of the Thermal Decomposition Process of Supported Silver Catalysts

Jun Jiang,Tianhao Xu,Yaping Li,Xiaodong Lei,Hui Zhang,D. G. Evans,Xiaoming Sun,Xue Duan 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.6

A deep understanding of the metallic silver catalysts formation process on oxide support and the formation mechanism is of great scientific and practical meaning for exploring better catalyst preparing procedures. Herein the thermal decomposition process of supported silver catalyst with silver oxalate as the silver precursor in the presence of ethylenediamine and ethanolamine is carefully investigated by employing a variety of characterization techniques including thermal analysis, in situ diffuse reflectance infrared Fourier transform spectroscopy, scanning electron microscopy, and X-ray diffraction. The formation mechanism of supported silver particles was revealed. Results showed that formation of metallic silver begins at about 100 oC and activation process is essentially complete below 145 oC. Formation of silver was accompanied by decomposition of oxalate group and removal of organic amines. Catalytic performance tests using the epoxidation of ethylene as a probe reaction showed that rapid activation (for 5 minutes) at a relatively low temperature (170 oC) afforded materials with optimum catalytic performance, since higher activation temperatures and/or longer activation times resulted in sintering of the silver particles.

A Deep Investigation of the Thermal Decomposition Process of Supported Silver Catalysts

Jiang, Jun,Xu, Tianhao,Li, Yaping,Lei, Xiaodong,Zhang, Hui,Evans, D.G.,Sun, Xiaoming,Duan, Xue Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.6

A deep understanding of the metallic silver catalysts formation process on oxide support and the formation mechanism is of great scientific and practical meaning for exploring better catalyst preparing procedures. Herein the thermal decomposition process of supported silver catalyst with silver oxalate as the silver precursor in the presence of ethylenediamine and ethanolamine is carefully investigated by employing a variety of characterization techniques including thermal analysis, in situ diffuse reflectance infrared Fourier transform spectroscopy, scanning electron microscopy, and X-ray diffraction. The formation mechanism of supported silver particles was revealed. Results showed that formation of metallic silver begins at about $100^{\circ}C$ and activation process is essentially complete below $145^{\circ}C$. Formation of silver was accompanied by decomposition of oxalate group and removal of organic amines. Catalytic performance tests using the epoxidation of ethylene as a probe reaction showed that rapid activation (for 5 minutes) at a relatively low temperature ($170^{\circ}C$) afforded materials with optimum catalytic performance, since higher activation temperatures and/or longer activation times resulted in sintering of the silver particles.

Automatic resonant frequency tracking for DCX‑LLC based on magnetizing current cancellation

Cheng Gu,Qinsong Qian,Dalin Xu,Tianhao Tan 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.1

The LLC resonant converter has been widely used as a DC-DC transformer (DCX) to provide a semi-regulated or unregulated bus voltage. However, due to circuit parameter variations, the switching frequency is usually different from the designed resonant frequency, which results in converter efficiency degradation. To achieve the highest efficiency under different scenarios, a novel primary-side regulation (PSR) scheme for LLCs based on magnetizing current cancellation is presented. The transformer magnetizing current component on the sampling resistor can be offset by the compensating current, which is generated by the auxiliary winding and the added compensating inductor. The effect of magnetizing current in the sampled primary resonant current can be effectively eliminated. Thus, the output current can be accurately estimated on the primary side of the LLC resonant converter. Finally, a prototype of a 20-60 V LLC is constructed to validate the theoretical analysis. In the experiment section, various scenarios are tested to assess the efficacy of the solution. It is shown that the LLC converter can always realize resonant frequency tracking with the highest transmission efficiency.

Effect of freezing on electrical properties and quality of thawed chicken breast meat

Ran Wei,Peng Wang,Minyi Han,Tianhao Chen,Xinglian Xu,Guanghong Zhou 아세아·태평양축산학회 2017 Animal Bioscience Vol.30 No.4

Objective: The objective of this research was to study the electrical properties and quality of frozen-thawed chicken breast meat and to investigate the relationship between these parameters at different times of frozen storage. Methods: Thawed samples of chicken breast muscles were evaluated after being kept in frozen storage at –18°C for different periods of time (1, 2, 3, 4, 5, 6, 7, and 8 months). Results: The results showed that water-holding capacity (WHC) and protein solubility decreased while thiobarbituric acid-reactive substances content increased with increasing storage time. The impedance module of samples decreased during 8-month frozen storage. Pearson correlation coefficients showed that the impedance change ratio (Q value) was significantly (p<0.05) related to pH, color, WHC, lipid oxidation and protein solubility, indicating a good relationship between the electrical properties and qualities of frozen-thawed chicken breast meat. Conclusion: Impedance measurement has a potential to assess the quality of frozen chicken meat combining with quality indices.

Novel central‑tapped planar transformer structure with natural current‑sharing for LLC resonant converters

Cheng Gu,Qinsong Qian,Dalin Xu,Tianhao Tan 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.9

Planar transformers have been widely used in isolated power supplies. However, with a large current density, the parallel windings usually cannot share the current evenly. This uneven current-sharing may cause additional winding losses, and damage the performance of the power converter. In this paper, a novel central-tapped planar transformer structure is proposed. Regardless of whether it is in the first half cycle or the second half cycle, the proposed twelve-layer transformer can be simplified as four three-layer transformers connected in parallel. Moreover, there is a “shielding layer” between adjacent three-layer transformers. In addition, the proposed transformer structure is optimized with a symmetrical layer arrangement, and the skin effect and proximity effect can be further reduced. Simulation and experimental tests indicate that the optimized planar transformer can stably provide 476.1 W of output power at a frequency of 1.25 MHz. The peak efficiency of the optimized transformer is up to 99.2%, and there is no obvious hot spot on the PCB board. It is noteworthy that the temperature difference in the secondary windings is less than 5 °C, which means the current-sharing in the secondary windings works well.