Applied Mechanics and Materials Vols. 229-231

Abstract: An optimization algorithm on the stator design of a dual function piezoelectric actuator was described in this paper. Four different sets of motors were investigated using various geometric parameters to determine the best design. The predicted prototype characteristics were in good agreement with the experimental results as well as the ANSYS simulation analyses. This optimization method can be used to enhance the motor output characteristics and efficiency.

Abstract: In this paper, a STM32F based on digital integral technology for Rogowski current transformer is studied. An analog integrator is used as an original model, and this model is discretized so that a digital integral formula is obtained. By using 32-bit microprocessor STM32F103C8T6, the integration of Rogowski coil output signal is realized. The experimental results show that the accuracy of the output by using this digital integral technology can reach 5P class defined IEC60044-8.

Abstract: This article describes a new novel single-stage PFC converter circuit based on active clamp forward. The circuit of the PFC converter and active clamp DC/DC converter together. It is suitable for a lot of the power supply application fields with simple structure & low cost. Also this article analyzes its detailed operating principle, and the circuit switches process especially. The experimental prototype test results show that the circuit topology to achieve the main switch & the auxiliary switch with the zero voltage turn-on, and the power factor being above 0.98, the efficiency being more than 88% at rated conditions.

Abstract: ±1000kV DC wall bushing under planning is a complex insulation system which bears the effects imposed by different working conditions. The electric field distribution is concentrated at the bushing outlet terminal, which might result in breakdown discharge especially when short-time abrupt conditions such as polarity reversal occur. In this paper, the finite element method is utilized to analyze electric field distribution and potential distribution of wall bushing during polarity reversal. Electric field distribution and potential distribution at the moment of polarity reversal are obtained, which provides value reference for the study of polarity reversal process.

Abstract: This article presents an improved dynamic surface control (IDSC) approach for DC-DC Buck converter with parameter uncertainties and external disturbances. For IDSC method, the parameters update laws are designed based on uncertainty equivalence criterion, the requirements to the controlled systems are reduced, and the problem of explosion of complexity can be overcome. The features of the derived controller are discussed and illustrated by the Simulation study. The analysis and simulation show that the obtained controller possesses good adaptability and robustness to system uncertainties.

Abstract: Based on space charge theory, electric field and potential distribution of ±1000kV DC wall bushing under DC and AC work condition is analyzed in this paper. The position and amount of space charge can be deduced from space charge theory and surface charge theory. By analyzing electric field and potential distribution under DC and AC voltage work condition with and without space charge, valuable conclusions are drawn, which provides valuable reference for insulation design.

Abstract: After introducing the new low-voltage protective electrical apparatus—Control and Protective Switching Device (CPS), there came to the importance and social benefits of its reliability. According to the study on CPS’s operation characteristics and failure modes, along with the current national standard and related industry standard, the two reliability indexes were proposed to measure CPS’s reliability for the first time, and the reliability compliance test plans were also provided. All the study did provide a reference for the reliability research work of CPS.

Abstract: A silicon carbide (SiC) vertical channel junction field effect transistor (VJFET) was fabricated based on in-house SiC epitaxial wafer with lift-off trenched and implanted method. Its blocking voltage exceeds 1300V at gate bias VG = -6V and forward drain current is in excess of 5A at gate bias VG = 3V and drain bias VD = 3V. The SiC VJFET device’s current density is 240A/cm2 at VG= 3V and VD = 3V, with related specific on-resistance 8.9mΩ•cm2. Further analysis reveals that the on-resistance depends greatly on ohmic contact resistance and the bonding spun gold. The specific on-resistance can be further reduced by improving the doping concentration of SiC channel epilayer and the device’s ohmic contact.

Abstract: In order to improve the flexibility of computer protection on relay protection and to simplify the development process, this paper presents a new method which a programmable logic is applied to relay protection in form of software and hardware platform. The method can better satisfy the needs of relay protection. Aiming at the shortage of traditional relay protection deceive, this paper mainly discuss how to realize the modularization of the new hardware and software platform and to make the theoretical analysis about logic hardware and software platform.

Abstract: With the aid of a two-dimensional thermal-electrical model, the thermal stability of multi-finger power heterojunction bipolar transistors (HBTs) with uniform segmented emitter, and non-uniform segmented emitter are studied. It shows that both of them could lower the peak temperature and improve the non-uniformity of the collector current density distribution, and thus improve the thermal stability, compared with an HBT which has traditional non-segmented emitter structure. At the same time, the improvement capability of thermal stability for HBT with non-uniform segmented emitter is superior to that of HBT with uniform segmented emitter, ascribing to selectively divide the emitter fingers into various segments according to the difference of heat dissipation capability in emitter fingers. Furthermore, the improvement capability of thermal stability for HBT with non-uniform segmented emitter is enhanced exponentially as segment spacing increases. However, for HBT with uniform segmented emitter, the ability is less sensitive to the increasing of the segment spacing as it exceeds 6μm. Therefore, the technique of non-uniform segmented emitter is a better method for enhancing the thermal stability of power HBTs.