Types Of Electrical Circuits Research Articles

КОМУТАЦІЙНИЙ СТРУМ ПЕРВИННОЇ ОБМОТКИ ТРАНСФОРМАТОРА ПРИ ВАРІАЦІЯХ СТРУМУ ЙОГО ХОЛОСТОГО ХОДУ

Transformers are an indispensable component of various types of electrical circuits. Various restrictions are imposed on the transformer switching operation, which are caused by the functional purpose of the systems, their configuration, parameters and characteristics of existing or available switching components or devices and associated transient processes. When the power transformer is switched on asynchronously, current surges in its primary winding, including in modes close to the min-imum load, may exceed its nominal current by several times. Such processes are undesirable from the point of view of energy efficiency, electromagnetic compatibility, transformer reliability and the functioning of protection systems. Proper analysis of electromagnetic processes was performed by numerical calculation methods followed by computer modeling using the MATLAB/Simulink software package. The purpose of the study is to highlight the extreme nature of switching current surges of the primary transformer and their dependence on the relative value of the no-load current of the winding. This current, in turn, depends on the slope of the main functional segment of the magnetization curve of the transformer core corresponding to its stationary mode of operation. The research shows that the increase in the idle speed of the transformer causes a directly proportional decrease in the switching current surges of the primary winding of the transformer. At the same time, the difference between the amplitude values of adjacent semi-periodic current surges decreases. It is noted that an increase in the value of the transformer's no-load current is often aimed at stabilizing the burning of the alternating currentarc in electric welding installations. They are characterized by a repeated short-term mode of switching, and therefore the determination of the mag-nitude of switching current surges is relevant here

ОРГАНІЗАЦІЯ АСИНХРОННОЇ КОМУТАЦІЇ ТРАНСФОРМАТОРА З УРАХУВАННЯМ ІНЕРЦІЙНОСТІ ЕЛЕКТРОМАГНІТНИХ ПРОЦЕСІВ

Transformers are an indispensable component of various types of electrical circuits. Various restrictions are imposed on the transformer switching operation, which are caused by the functional purpose of the systems, their configuration, parameters and characteristics of existing or available switching components or devices and associated transient processes.When the power transformer is switched on asynchronously, current surges in its primary winding, including in modes close to the minimum load, may exceed its nominal current by several times. Such processes are undesirable from the point of view of energy efficiency, electromagnetic compatibility, transformer reliability and the functioning of protection systems. The purpose of the study is to organize the switching of the transformer in such a way that it achieves its output to a stable mode of operation with a minimum amplitude of the input current and the duration of the transition process, without extreme manifestations in the switching process.Algebraic, graphic, and simulation-visual aspects of the analysis of the processes occurring during power transformer commutation are considered in the work. It is shown that the repeated switching on of the transformer can lead to a significantly larger current surge in the primary winding compared to the first switching on, and the reason for this phenomenon is the magnitude of the magnetic flux at the time of repeated commutation. It is shown that the value of the flux and its change depends on the amount of load on the secondary winding, and lower values of the load correspond to higher values of the rate of decline of the magnetic flux of the transformer core and vice versa. The following switching algorithm of the transformer is recommended, in which each subsequent switching on of the transformer will start with a close to zero value of the magnetic field flux

Adaptive-passive control of structure-borne noise of rotating machinery using a pair of shunted inertial actuators

In this article, two piezo-based rotating inertial actuators are considered for the suppression of the structure-borne noise radiated from rotating machinery. Each inertial actuator comprises a piezoelectric stack element shunted with the Antoniou’s gyrator circuit. This type of electrical circuit can be used to emulate a variable inductance. By varying the shunt inductance it is possible to realise two tuneable vibration neutralisers to suppress tonal frequency vibrations of a slowly rotating machine. Also, reductions in the noise radiated from the machine housing can be achieved. First, a theoretical study is performed using a simplified lumped parameter model of the system at hand. The simplified model consists of a rotating shaft and two perpendicularly mounted shunted piezo-based rotating inertial actuators. Second, the shunted piezo-based rotating inertial actuators are tested on an experimental test bed comprising a rotating shaft mounted in a frame. The noise is radiated by a plate that is attached to the frame. The experimental results show that a reduction of 11 dB on the disturbance force transmitted from the rotating shaft through the bearing to the housing can be achieved. This also generates a reduction of 9 dB for the plate vibration and the radiated noise.

Rietveld refinements, impedance spectroscopy and phase transition of the polycrystalline ZnMoO4 ceramics

The triclinic phase of zinc molybdate α-ZnMoO4 (ZMO) was synthesized by a simple co-precipitation method at 600°C. The crystal structure of the obtained polycrystalline sample of ZMO was characterized by X-ray diffraction (XRD) and Rietveld calculations using the space group P-1. The electrical properties of α-ZnMoO4 compacted pellets were determined at room temperature from electrical impedance spectrometry (EIS), in the temperature range of 400–700°C. Nyquist representations were interpreted in terms of two types of electrical circuits, involving a high frequency bulk component and a low frequency Warburg component. Analyses of the frequency dependence of the real and imaginary impedance show a non-Debye type relaxation. A phase transition corresponding to the allotropic transformation triclinic–monoclinic (α→β) of ZnMoO4 was observed in the temperature range of 450–500°C, with a variation of activation energies. The Warburg component is discussed in terms of electrode surface reactions.

Fabrication, electrical characterization, and detection application of graphene-sheet-based electrical circuits

The distribution of potential, electric field, and gradient of square of electric field was simulated via a finite element method for dielectrophoresis (DEP) assembly. Then reduced graphene oxide sheets (RGOS)- and graphene oxide sheets (GOS)-based electrical circuits were fabricated via DEP assembly. The mechanically exfoliated graphene sheets (MEGS)-based electrical circuit was also fabricated for comparison. The electrical transport properties of three types of graphene-based electrical circuits were measured. The MEGS-based electrical circuit possesses the best electrical conductivity, and the GOS-based electrical circuit has the poorest electrical conductivity among all three circuits. The three types of electrical circuits were applied for the detection of copper ions (Cu2+). The RGOS-based electrical circuit can detect the Cu2+ when the concentration of Cu2+ was as low as 10 nM in solution. The GOS-based electrical circuit can only detect Cu2+ after chemical reduction. The possible mechanism of electron transfer was proposed for the detection. The facile fabrication method and excellent performance imply the RGOS-based electrical circuit has great potential to be applied to metal ion sensors.

Entropy production in linear Langevin systems

We study the entropy production rate in systems described by linear Langevin equations, containing mixed even and odd variables under time reversal. Exact formulas are derived for several important quantities in terms only of the means and covariances of the random variables in question. These include the total rate of change of the entropy, the entropy production rate, the entropy flux rate and the three components of the entropy production. All equations are cast in a way suitable for large-scale analysis of linear Langevin systems. Our results are also applied to different types of electrical circuits, which suitably illustrate the most relevant aspects of the problem.

Development of a piezoelectric proton exchange membrane fuel cell stack (PZT-Stack)

Previous studies report that bi-cell piezoelectric proton exchange membrane fuel cells with a nozzle and a diffuser have been successfully developed, and this pseudo-bipolar design is expected to benefit the future development of the piezoelectric stack (PZT-Stack). In this study, an innovative PZT-Stack design composed of three L-PZT-D-type bi-cells contains a total reaction area of 24 cm2 with a diffuser angle (θ) of 10°, a channel path (L) of 5.63 mm, and a channel opening width (D) of 1 mm. To optimize the performance of the PZT-Stack, the module is investigated under various operating conditions, including the PZT vibration frequency, the cell temperature, the relative humidity in the anode, the type of electrical circuit, and the type of intake module on the anode. The stability and the performance of a PZT-Stack with a degraded membrane electrode assemblies (MEA) are analyzed. Although the degraded working mode lowers the performance of the PZT-Stack, the module is still able to function consistently and deliver positive power. The maximum net power of the PZT-Stack was 3.8627 W under a PZT frequency of 60 Hz, and a cell temperature of 50 °C in a parallel electrical circuit.

A heuristic approach for constructing symmetric Gray codes

Interest in the symmetric Gray (SG) code is high because of its importance in the design and testing of many types of electrical circuits and information systems. The conventional methods for constructing such a code are complicated. A heuristic approach is described in this paper. Examples of constructing the SG code of order 5, 6, and 7 are included.

A number of models for CPA impedances of conductors and for relaxation in non-Debye dielectrics

The impedance, admittance, or permittance diagrams of materials, when presented in the complex plane, are often well defined straight lines, or well defined semi-circles with axes depressed below the real axis. Using a general theoretical approach, it is suggested that this behavior is not characteristic of a single particular phenomenon or theory (hence, not characteristic of fractal geometry for example). The potential difference, V( t), causing a current, I( t), to flow in any type of electrical circuit, can be expressed in terms of the ‘fractional derivative’ of the current: V = Pfrsol| Pd vgn I/ dt ν where P (‘phasance’, magnitude) and ν (degree of fractional derivation) depend on the physical properties. A particular case corresponds to constant P and ν, to a constant energy efficiency, to a straight line on the complex impedance diagram and to the ‘constant phase angle’ (CPA) behavior. As an example, the direct application of the mathematical theory leads to several simple and exact distribution functions of relaxation times and a number of models for non-Debye dielectrics.

Creativity in a cooperative group setting

AbstractThis study was to determine whether cooperative small groups would stimulate creativity of fith and sixth grade students more than an individualized learning environment. Student aptitudes for creative and academic work were assessed on the Torrance Tests of Creative Thinking (Verbal Form A), analysis of student created electrical circuit diagrams, and a batteries and bulbs prediction test. A measure of student perceptions was also used to indicate any changes in attitudes toward the science activity and learning environment. A posttest control group design was used with 11 I fifth and sixth grade students. Half of the population worked by themselves, while the other half (experimental) worked in a student‐structured environment on the same science activity which involved creating as many different types of electrical circuits from a given set of batteries and bulbs as possible. An overall conclusion is that fifth and sixth grade students working within small cooperative groups can be more creative as measured by a figural creativity test with electrical circuits than students working alone. The implication of this study is that small cooperative groups as well as individualized groups should be used in elementary science classes when creativity is one of the instructional objectives.

Electronic oscillations in positive-grid triodes, and resonance oscillations in magnetron generators

The paper describes the results of experiments made to determine the factors controlling the production and wavelength of those oscillations, usually termed electronic, which are produced in positive-grid triodes and the frequency of which depends primarily on the inter-electrode time of transit of the electrons. The frequency of the oscillations obtained in this way is so high (of the order of 109 cycles per sec.) that it is not possible at present to measure the dynamic characteristics of the valve used to produce them. It is shown in the paper that oscillations similar in character to the electronic oscillations obtained with positive-grid triodes can be obtained with the split-anode magnetron, at magnetic field intensities greater than the critical field at which the anode current decreases rapidly with increase in magnetic field. The frequency of these electronic oscillations is proportional approximately to the ratio of the anode potential and the magnetic field intensity applied to the magnetron, and by suitable choice of this ratio the frequency of the oscillations can be made low enough for ordinary radio-frequency measurements to be made on valve impedance in the neighbourhood of oscillation. This procedure was followed in the experiments described in the paper; and the results obtained at a series of frequencies between 6 and 15 megacycles per sec. indicate that, in the case of the magnetron, the valve reactance changes sign in the neighbourhood of these electronic oscillations. An analysis is given of the type of electrical circuit equivalent to the magnetron valve required to reproduce the type of reactance and resistance variation obtained experimentally. It is shown that this equivalent circuit is of the series form having negative inductance, negative capacitance, and negative resistance components, and that this type of equivalent circuit could be produced if the inter-electrode transit time of the electrons within the valve were comparable with the period of oscillations generated by the valve. Oscillations without any marked change in valve reactance were also obtained in the magnetron near the critical field condition.

The Theory of the Operation of the Howling Telephone with Experimental Confirmation

A general theory of the sustained oscillations of electro-mechanical systems is presented in the paper. The electrodynamical properties of the telephone transmitter and receiver are described and sufficient numerical data are given to enable one to calculate the intensity and frequency of howling for various types of systems. Detailed consideration is given to the following three systems, namely, one where the transmitter and receiver disphragms are coupled together mechanically by a lever system, one where they are coupled by a small box of air, and one where they are coupled by a long tube of air. The type of electrical circuit to use with each of these systems depends upon the type of performance desired.