Influence Of Current Frequency Research Articles

Space Charge Limited Current and Induced Particle Reflection With a Time-Varying Current Injection

Properties of space charge limited current and induced particle reflection with a time-varying current injection are investigated by an efficient grid-free numerical approach. Considering a planar diode with a single-frequency current emitted parallel to the upstream electrode surface, we study the current transmission characteristics between two dc biased electrodes and the influence of current frequency and magnitude on the limiting current first leading to electrons reflection. It is found that on account of the time-varying current injection, the limiting current strongly depends on the current frequency and magnitude, as well as the emission velocity of electrons. For the low-frequency limit, the dc component of the limiting current is approximately equal to half of that obtained from the time-independent model. The limiting current increases monotonically with increasing the frequency, and the dc component has a maximum equal to the limiting current obtained from the time-independent model.

Вплив частоти струму на технологічні та енергетичні характеристики скребперних установок для прибирання гною

Вплив частоти струму на технологічні та енергетичні характеристики скребперних установок для прибирання гною

Iron Loss Calculation in Permanent Magnet Machines Under Unconventional Operations

This paper investigates the iron loss calculation of permanent magnet (PM) machines undertaking unconventional operations, where the high-frequency alternating armature field is only a fraction of the constant PM field. It is found that the iron loss of PM machines undertaking such unconventional operations cannot be calculated reliably as the conventional summation of all the iron loss harmonics predicted by finite-element (FE) methods due to fake iron loss harmonics. Further investigation is conducted on the influence of current frequency and magnitude, FE mesh, and convergence tolerance on the FE predicted iron loss under unconventional operations. It is then proposed in this paper that the iron loss of PM machines undertaking unconventional operations can be calculated as the summation of only the iron loss harmonics, which are insensitive to the convergence tolerance. The analyses are validated by the experimental results.

Influence of Power Supply Frequency on Microstructure and Properties of Micro-Arc Oxidation Coating on Aluminium Alloy

This paper studies the influence of current frequency on the micro-arc oxidation (MAO) process, microstructrue and the properties of the formed alumina coatings. The amount of discharge sparks increases and the spark moves more quickly with increasing the frequency of current pulse. SEM results show that the size of the discharge products decreases. The anodic cell voltage decreases with increasing the frequency of power supply, however, the cathodic cell voltage increases. The thickness and roughness of the coating produced using frequency of power supply 50 Hz are high. Increasing the frequency, the thickness of the coating decreases, but coating surface becomes even, and the coating possesses better corrosion protective property

Numerical simulation of horizontal continuous casting process of round copper billet with electromagnetic stirring

In this paper, a comprehensive three-dimensional mathematical model is built to investigate the effect of rotating electromagnetic stirring on the solidification process of copper round billet during horizontal continuous casting. The electromagnetic field was simulated by ANSYS software, and the thermal flow field was simulated by FLUENT software. The coupling between the electromagnetic field and the thermal flow field was implemented by a user defined subroutine. The simulation results match with the experiment ones. The influence of current frequency and current intensity on the flow field of molten melt was investigated. The optimum current intensity and frequency are found to be 40 A and 10 Hz when the maximum magnetic flux density and the time average electromagnetic force are 100 mT and 72×10−3 N respectively on the surface of the round copper billet.

Microstructure and 3D microtomographic characterization of porosity of MAO surface layers formed on aluminium and 2214-T6 alloy

A fine characterization of the microstructure of the MAO coatings formed on aluminium (purity 99,999%) and its alloy 2214-T6 was observed using field emission gun scanning electron microscopy (FEG-SEM) with energy dispersive spectrometry (EDS) and X-ray microtomography (XMT). In addition, the influence of current frequency (pure aluminium) and the precipitates of substrate were investigated (case of 2214-T6 alloy). The MAO surface layers formed on aluminium and its alloy 2214-T6 can be divided into two parts: the outer layer with high porosity (so-call porous layer) and the inner layer with low porosity (so-call dense layer). However, the porosity of the inner layer increases toward the MAO layer/substrate interface. It is found that, both the thickness and the porosity increase when the current frequency decreases. The porosity of the MAO coating can be attributed to discharges formation in the vicinity of the MAO coating/substrate interface. In the particular case of 2214-T6 aluminium alloy (3.9% Cu), with coarse non-valve metal rich precipitates aligned perpendicular to the surface of the work electrode; the transformation of precipitates under discharge effect can provoke the formation of big channels, which go through the MAO surface layer. This last one induces local formation of a layer rich electrolyte species toward the substrate.

Study of the influence of current frequency and non-magnetic gap value on the efficiency of Al-alloys stirring in metallurgical furnaces

Study of the influence of current frequency and non-magnetic gap value on the efficiency of Al-alloys stirring in metallurgical furnaces