Turn-off modes of silicon carbide MOSFETs for short-circuit fault protection

Zhang, Jianzhong,Wu, Haifu,Zhang, Yaqian,Zhao, Jin The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.2

With the rapid development of semiconductor technology, the applications of silicon carbide (SiC) MOSFETs have been booming in recent years, where short-circuit fault protection plays an important role. In this paper, voltage and current waveforms under different short-circuit faults are analyzed. Then, two types of turn-off modes, namely a soft turn-off mode and a two-stage turn-off mode are introduced. The peak voltage, short-circuit energy and anti-interference performances of SiC MOSFETs under the different turn-off modes are analyzed and compared at various DC bus voltages. The obtained experimental results show that the soft turn-off mode can reduce voltage spikes. However, it needs a blanking time to improve the anti-interference performance of the system, which increases the short-circuit energy. For the two-stage turn-off mode, the anti-interference performance of the system is improved and the short-circuit energy is obviously decreased. However, the peak voltage generated by the two-stage turn-off mode is slightly larger than that of the soft turn-off mode. On the whole, the two-stage turn-off mode is more competitive than the soft turn-off mode for the short-circuit fault protection of SiC MOSFETs.

Adaptive flow optimization of a turbocharger compressor to improve engine low speed performance

Yangjun Zhang,Chenfang Wang,Zheng Xinqian,Weilin Zhuge,Yulin Wu,Jianzhong Xu 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.6

To improve the engine overall performance, an adaptive flow optimization procedure is proposed in this paper to synthesize turbocharger compressor optimum designs. Two objective functions are involved in the adaptive optimization. They are the traditional compressor design and the compressor design with consideration of improving engine overall performance. The two-step decomposition approach is chosen to generate optimum designs. The optimized designs not only satisfy turbomachinery and engine constraints but also have optimum objective function values in the two fields. Performance sensitivity analysis of compressor main design variables is performed for the flow optimization design process. A centrifugal compressor is redesigned for a turbocharged gasoline engine, as an example, based on the adaptive flow optimization process. The calculating results show a more than 5% increase of isentropic efficiency in comparison with the base line compressor, resulting in a more than 19% increase of engine torque at low speed conditions.

Effect of Fibers on the Flow Property of Turbulent Fiber Suspensions in a Contraction

Lin, Jianzhong,Zhang Shanliang,Olson James A. The Korean Fiber Society 2007 Fibers and polymers Vol.8 No.1

In the flow of turbulent fiber suspensions flowing through a contraction with rectangular cross-section, the Reynolds averaged Navier-Stokes equation with the term of additional stress resulting from fibers was solved with the Reynolds stress model to get distributions of the mean velocity, mean pressure, turbulent kinetic energy and turbulent dissipation. It is found that the mean velocities at exit are small around the center and large near the wall for higher concentration. Fibers reduce turbulent intensity and turbulent dissipation at central line, but enhance them over the cross section at exit. Fibers have no effect of restraint on the turbulence in the contraction flow. The additional stress resulting from fibers plays a role in the increase of drag.

Electrochemical Polishing of Additively Manufactured Ti–6Al–4V Alloy

Yifei Zhang,Jianzhong Li,Shuanghang Che,Yanwen Tian 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.6

In this present paper, the electropolishing behavior of Ti–6Al–4V alloy fabricated by additive manufacturing in chloridecontainingethylene glycol electrolyte was surveyed. The impacts of chloride ion on surface quality and oxide film ofTi–6Al–4V were analyzed in dependence on the surface topography, roughness, weight loss ratio and compositions. Thevisual and microscopic results revealed that the optimally electropolished surface was attained in a 0.4 mol L−1 chlorideelectrolyte with a decreased surface roughness of 75.04% and a weight loss rate of 4.93%. For lower (CCl−1 ≤ 0.3 mol L−1)or higher concentrations (CCl−1 ≥ 0.5 mol L−1), a smooth and flat surface was not observed due to insufficient reactions orexcessive anodic dissolution. During the electropolishing, the titanium oxides nucleated and corresponding surface tensionincreased, resulting in the formation of a stable TiO2film on the surface of the Ti–6Al–4V alloy, increasing the corrosionresistance of the specimen.

Elastic buckling performance of FG porous plates embedded between CNTRC piezoelectric patches based on a novel quasi 3D-HSDT in hygrothermal environment

Yujie Zhang,Zhihang Guo,Yimin Gong,Jianzhong Shi,Mohamed Hechmi El Ouni,Farhan Alhosny Techno-Press 2023 Advances in nano research Vol.15 No.2

The under-evaluation structure includes a functionally graded porous (FGP) core which is confined by two piezoelectric carbon nanotubes reinforced composite (CNTRC) layers. The whole structure rests on the Pasternak foundation. Using quasi-3D hyperbolic shear deformation theory, governing equations of a sandwich plate are driven. Moreover, face sheets are subjected to the electric field and the whole model is under thermal loading. The properties of all layers alter continuously along with thickness direction due to the CNTs and pores distributions. By conducting the current study, the results emerged in detail to assess the effects of different parameters on buckling of structure. As instance, it is revealed that highest and lowest critical buckling load and consequently stiffness, is due to the V-A and A-V CNTs dispersion type, respectively. Furthermore, it is revealed that by porosity coefficient enhancement, critical buckling load and consequently, stiffness reduces dramatically. Current paper results can be used in various high-tech industries as aerospace factories.

Virtual Disassembly

Mo, Jianzhong,Zhang, Qiong,Gadh, Rajit Society for Computational Design and Engineering 2002 International Journal of CAD/CAM Vol.2 No.1

De-manufacturing is an entire process of collecting, disassembling, reusing, refurbishing, recycling, and/or disposing products that are obsolete or un-repairable. Designing the products for inexpensive and efficient disassembly enhances the ease of de-manufacturing. Virtual disassembly addresses the difficulty and the methods to disassemble a product in design stage rather than really disassemble a product at the end of its life cycle. Based on the virtual disassembly analysis results, design will be improved for better assembling/disassembling. This paper presents a systematic virtual disassembly methodology such as disassembly relation modeling, path/sequence automatic generation and evaluation. This paper also presents a new virtual disassembly interface paradigm via virtual reality technology for disassembly simulation in virtual environment.

Life-Cycle Reliability Evaluation of Semi-Rigid Materials Based on Modulus Degradation Model

Jiupeng Zhang,Shengchao Cui,Jun Cai,Jianzhong Pei,Yanshun Jia 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.6

The dynamic modulus of semi-rigid material is one of the important material parameters widely used in the design and evaluate ofasphalt pavement, which has a great effect on the reliability, healthy condition and service life of pavement. To show the three-phasedegradation process of dynamic modulus accurately and calculate the time-dependent reliability based on fatigue damage, thedegradation models based on non-linear fatigue damage and improved Wei-bull distribution modulus degradation are established andtestified in this paper, considering the threshold of normalized modulus. Then the reliability models based on the two abovedegradation process models are evaluated. Finally, the reliability analysis procedure is established using Monte Carlo (MC) methodand the corresponding calculation is conducted using Matlab. Cement stabilized macadam is used as an example in this paper. Results show that non-linear fatigue damage and improved Wei-bull distribution modulus degradation models can indicate threephasedegradation process of semi-rigid material modulus better and the reliability based on the proposed two models was moreaccurate to the actual situation.

EFFECT OF ASYMMETRICAL STAND STIFFNESS ON HOT ROLLED STRIP SHAPE

DIANYAO GONG,JIANZHONG XU,ZHENG JIANG,XIAOMING ZHANG,XUZNGHUA LIU,GUODONG WANG 한국소성가공학회 2008 한국소성가공학회 컨퍼런스 Vol.2008 No.10

Inter‑turn short‑circuit fault detection with high‑frequency signal injection for inverter‑fed PMSM systems

Zheng Xu,Jianzhong Zhang,Zakiud Din,Yongbin Wu,Ming Cheng 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.6

This paper develops an online inter-turn short-circuit fault (ISF) detection method for inverter-fed permanent magnet synchronous machine (PMSM) systems. A high-frequency (HF) mathematical model of a PMSM with an ISF is established. Based on the presented HF model, the HF responses of the PMSM with various severity of ISF under HF voltage injectionare analyzed in detail, where both the short-circuit ratio and the fault resistance are considered to evaluate the fault severity. In the proposed fault diagnosis method, the amplitude of the HF negative-sequence component is used to determine the fault severity, and the initial phase is used to locate the position of the faulty phase. The simulation and experimental results verify the effectiveness of the proposed method.

Active power decoupling method for single‑phase PWM converters without LC branch sensors

Jian Xiong,Jianzhong Zhang,Zheng Xu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.7

The presence of ripple power in a converter system has a negative influence on both control performance and reliability. Active power decoupling (APD) is a practical technique to deal with such problems. However, the APD method requires extra sensors on the LC branch, which increases the complexity and cost of the control system. This paper puts forward a new APD method to handle undesirable ripple power for H-bridge PWM converters. When compared with previous APD methods, the proposed APD method eliminates the current and voltage sensors on the LC branch by utilizing a ripple voltage control loop. Then, both the cost and reliability of the converter system are improved. To improve the control performance, an APD method that only has a voltage sensor in the LC branch is also discussed. Simulation results show that the DC-link voltage ripples can be decreased due to the application of the proposed APD method. Finally, the effectiveness of the proposed method is verified by the experimental results.