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Triggered vacuum switch (TVS) has tiny turn-on time, huge power capacity and breaking ability in zero-crossing, and can be used to implement controlled reclosing technology. However, TVS has to break circuit reliably in zero-crossing. The reclosing peak current and transient voltage in 10 kV lines was estimated to determine the electrical transient parameters that the TVS worked with, and then an...
A novel minimized microstrip planar antenna with pre-controllable resonant frequency and impedance matching is presented for microwave engineering applications. Double-sided planar structure is adopted to build the resonant loop of the antenna. The tuning of the impedance matching and the resonant frequency is studied, and the impedance matching and resonant frequency can be adjusted independently...
Electromagnetic limited-angle torque motors (LATMs) which have a limited angular movement less than 180 degrees are widely applied in industry, particularly for positioning tasks. Compared with common rotating motors, LATMs have many advantages such as simple structure, high reliability, and uncomplicated control mode. In general, radial-flux permanent-magnet LATMs have two conventional types which...
Electric Machine is an energy conversion device, which realizes the electrical energy and mechanical energy convert to each other through electromagnetic power or electromagnetic torque. Electromagnetic torque is an important medium for this conversion progress. Thus accurate estimation or model of electromagnetic torque is desired for designing and analyzing the electric machines. Furthermore electromagnetic...
Permanent magnet synchronous motor (PMSM) has been widely used in household appliances, medical instruments and vehicles. Electromagnetic interference (EMI) is a challenging problem for PMSM drive system fed by pulse width modulation (PWM) inverter because of the reason that EMI noise generates undesirable influences on control system such as communication errors, degraded equipment performance and...
PMSMs with concentrated windings gain more and more interests due to the very short end winding and advantages in the production process, for which they are desirable for wind power generations, electric vehicles and torque propulsion and so on [1]. However, concentrated windings produce a rich spectrum of flux density harmonics, which rotate asynchronously with respect to the rotor, inducing eddy...
As the level of short-circuit fault current gradually approaches the maximum value that the breaker can cut off, effective ways to limit it have to be found. The saturated-core superconducting fault current limiter (SCSFCL) is a kind of current-limiting device based on the nonlinear activity of the steel core.
Permanent magnet synchronous machines (PMSM) have high torque density, efficiency, power factor and so on compared with other type of machines. PMSMs can be separated into traditional well-known distributed wounded (DW) machines and fractional slot concentrated winding (FSCW) machines [1]. FSCW machines own low cogging torque, compact structure, high power density, and convenient fabrication, etc...
FSCW SPM machines (SPP <1/2, such as 10-pole/12-slot), own outstanding constant power ability [1], although it was regard widely that only IPM machines can be flux-weakened deeply. SPM machines are considered as a favorite candidate for electric propulsion and vehicle application, in order to take their other advantages, such as convenient fabrication, and good controllability [2]. The constant...
Concerned with loss of excitation (LOE) protection for large hydro-generators, several engineering issues with their improvement approaches are investigated. Based on the analysis of the variable excitation voltage criterion on its principle, performance and application, it's indicated that the expected function advantages of the criterion are actually not available, bringing about more potential...
The Casimir force originates from quantum fluctuations. While this force is too weak to have any measurable effects between objects at separations larger than ~ 10 μm it dominates the interaction between electrically neutral surfaces at the nanoscale. By fabricating a doubly clamped microbeam for sensing the force and a comb actuator to control the distance, we demonstrate that the Casimir force can...
We examine the seemingly frequency-dependent gate leakage current component of frequency-modulated charge pumping and show it to be a measurement artifact. If untreated, this results in erroneous defect density extractions. We present a constant shape factor methodology to suppress this component such that frequency-modulated charge pumping is well positioned for advanced device defect characterization.
This letter reports the integration of high-Q vertical ring inductors on individual small CMOS chips using a novel chip embedding technique. A small CMOS voltage controlled oscillator (VCO) chip which has 2×2mm2 in size and 5.8 GHz of operating frequency was used for post integration. The chip embedding technique enables the post-CMOS processing on such a tiny individual chip. The integration of vertical...
In the growth of GaAsP nanowires on GaAs (001) substrates, it was found that the P concentrations in the nanowires and unintentional two-dimensional (2D) GaAsP layer are different. Possible explanations are given.
To understand the growth mechanism and the effect of catalysts in growing III–V epitaxial nanowires, GaAs (111)B substrates with Au thin films were annealed in a molecular beam epitaxy (MBE) system. Scanning/transmission electron microscopy (SEM/TEM) investigations indicate that, during annealing, the Au catalysts were formed and affect significantly the surface morphology of the GaAs substrates.
To explore the growth mechanism and the effect of non-gold catalysts in growing III–V epitaxial nanowires, InAs nanowires were grown on GaAs(111)B substrates using annealed Pd thin film as catalyst. Through detailed scanning and transmission electron microscopy (SEM/TEM) characterisations, it is found that when the catalyst size is less than 50 nm (from annealing the Pd thin film), defect-free zinc-blende...
A novel phenomenon of an asymmetric shell formation is observed within the zinc blende structured InGaAs nanowires. It is found that three Ga-rich zones are formed along <112>A directions, while three In-rich zones are formed along <112>B directions in the truncated-triangular shells. The polarity-driven lattice latching effect is accounted for this compositional inhomogeneity...
The Casimir force arising from quantum fluctuations could become the dominant interaction in silicon micromechanical devices under the appropriate conditions. The measured force is distinct from the pairwise summation of van der Waals forces.
A finite element model is used for flexural vibration analysis of a static (non-rotating) rotor with two open cracks, and the stiffness matrices of the cracked elements are obtained using transfer matrix analysis and local flexibility theorem. Through numerical simulation, the effects of the slenderness ratio and the crack depth on the mode shapes and the changes in the eigenfrequencies of the cracked...
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