Electromagnetic Apparatus Research Articles

Radio frequency animal identification: electromagnetic analysis and experimental evaluation of the transponder-gate system

In this paper we present some theoretical and experimental results in the investigation of the electromagnetic setup for Radio Frequency Identificaiton (RFID), that is, a complex environment in which a reader–transponder system operates for the recognition and classification of animals. This kind of system is becoming very popular in some market branches (e.g. the bovine meat market) and we present here also an experimental analysis of the bovine meat process steps, localising possible sources of electromagnetic noise in the standardised frequency range of RFID. In particular, the system under analysis is composed of a portable reader (Innoceramics P3000) and passive glass tags (boli) working in Half-Duplex (HDX) at frequencies of 123.2 kHz and 134.2 kHz (field strength ~106 dbµV/m, reading distance about 25 cm).

Morphological change of semiconductor growth interface from solution in a magnetic field

In the present study, the morphological changes of a semiconductor growth interface from a solution were observed by near-infrared microscopy in rotating and static magnetic fields generated by two kinds of electromagnetic setups. The rotating magnetic setup had a maximum magnetic induction of 12 mT with a frequency of 50 Hz at the center of the furnace. The static magnetic field was produced by a single solenoid with a maximum magnetic induction of 800 mT. The growth of GaP/GaP (1 1 1) B was performed by a linear cooling method at the rate of 1 K/min under a starting growth temperature of 1173 K. The results revealed few differences in the morphological changes during growth under constant rotating magnetic fields of 0 and 12 mT. It was shown that the transverse static magnetic field of 800 mT reduced the growth rate and suppressed the appearance of macrosteps on the facet region.

Détermination par méthode électromagnétique de la concentration en sel d’un sol irrigué

A prerequisite for the control of salinity in soils is the determination of the salinity of the upper first metre of the soil with the greatest accuracy. This is commonly done from saturated paste extracts but on too small a volume and too restricted a number of samples. This must be done without modification of the soil structure and on a sufficiently narrow grid. Electromagnetic conductivity meters of Slingram type are convenient to indirectly determine the salinity by measurement of electrical conductivity. However the depth of investigation commonly exceeds the first metre and the saturated salted zone beneath significantly influences the results. A theoretical study together with a complete calibration test on the border of Chott El Guettar (Tunisia) confirms that short coil separation (60 cm) increases the sensitivity of the apparatus to conductivity variations in the first metre of soil. Key words: Saline soils, electrical conductivity, electromagnetic apparatus

Electromagnetic method and apparatus for the treatment of radioactive material-containing volumes

Electromagnetic method and apparatus for the treatment of radioactive material-containing volumes

High-speed and high-thrust linear induction motor designed by using eigenvalue analysis method

The effectiveness of a novel design technique, called the EVA eigenvalue analysis method, for the electromagnetic force maximization problem is examined. EVA is an approach to elucidate the essential characteristics of an electromagnetic apparatus. The EVA method was used to design the magnetomotive forces of an ideal high-speed LIM (linear induction motor) and it was shown that the thrust per apparent power and other characteristics of the LIM can be improved. The EVA method allows design calculations to be made for general machines using the electromagnetic induction phenomenon as a principle.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Aging of Electrical Appliances Due to Harnmonics of the Power System's Voltage

Average values for the exponents of a weighted harmonic factor are derived for transformers, induction and universal machines as they occur in electrical appliances. The derivation is based on a theoretical loss analysis and on experimentally obtained temperature data [1,2]. The influence of the temperature on the lifetime of the above electromagnetic devices is discussed. An attempt has been made to recommend a limit for the value of the weighted harmonic factor which indirectly limits the sum of the weighted amplitudes of occurring voltage harmonics in a distribution system. Thus a criterion has been devised which judges harmonic voltage spectra based on the temperature increase they produce in an electromagnetic apparatus. As an example, two possible sets of voltage harmonic spectra are discussed that would protect consumers, as well as utility systems, from adverse effects. The work described has been supported by the U.S. Department of Energy.

The contamination of metallic surfaces by small particles impacting with low velocities

The contamination of metallic surfaces was investigated at the laboratory of the Lehrstuhl für Raumfahrttechnik (LRT) of the Technische Universität München (TUM) for small particles with low velocities. This paper contains a description of the electromagnetic accelerator setup which is capable of obtaining the impact velocity between 10 and 400 m/s with particle masses up to 1 g. The evaluation method for the ratio of adhering to impacting particles is described. Various metallic targets were tested with respect to their contamination rate using different types of particles from 1 to 500 μm in size for simulation of space debris. The results are presented with emphasis on the adhesion mechanisms. Particular influences on the contamination rate are discussed.

Metallic dust collectors for low velocity impacts

Experiments simulating the non-destructive collection of cosmic dust are conducted at the laboratory of the Lehrstuhl für Raumfahrttechnik (LRT) of the Technische Universität München (TUM). The electromagnetic accelerator setup is described, which is capable of obtaining an impact velocity between 10 and 400 m/s with particle masses up to 1 g. The evaluation method of the ratio of collected to impacting particles is given. Various metallic surface structures were tested with respect to their collection efficiency using different types of particles from 1 to 500 μm in size for simulation of cosmic dust. The simulation results are presented with emphasis on collection mechanisms. Particular influences on the collection mechanisms are discussed.

Utilization of a helmholtz coil in the electromagnetic method

The purpose of this paper is to develop a pulse electromagnet that is convenient for utilization under laboratory conditions and that will produce a homogenous magnetic field. Two kinds of Helmholtz coils--one with a twenty centimeter diameter fabricated from a sprint-slab, and one with a steel transferable coil--are used in this paper. The pulse current is produced, the magnetic field in the coils are computed, and records of signals are presented. Therefore, a simple electromagnetic apparatus, based on a Helmholtz coil, has been developed.

Interactive computer aided design of electric machines and electromagnetic apparatus (invited)

The design of electromagnetic devices in industry is still largely done using traditional techniques. Early computing facilities were costly to use and limited to alphanumeric applications. The application of numerical methods, mainly finite elements, to the solution of electromagnetic field problems, proved to be difficult to implement initially due to input/output problems. These difficulties were completely obviated by the advent of inexpensive microcomputers and low cost interactive graphics. However, it is still uncommon to find these new methods being employed as part of the normal electrical design process. Meanwhile, in parallel, there has been a massive growth of computer-aided methods applied to all aspects of mechanical engineering design and drafting, CADCAM. The trend is towards small, powerful, expandable, dedicated computer systems equipped with high resolution interactive graphics, which can be connected via a fast datalink. These are commonly available, complete with software, as turnkey systems. The advantages of CADCAM are manifold: Lower costs, higher productivity, higher quality products, with shorter lead times. The introduction of CADCAM will result in organisational as well as technical changes. The major change will be in the way people think.

Pulverization of ferric oxide in an electromagnetic apparatus

Pulverization of ferric oxide in an electromagnetic apparatus

Preparation of titanium dioxide suspensions in electromagnetic apparatus

Preparation of titanium dioxide suspensions in electromagnetic apparatus

Analysis Of Torque-Speed Curves Of Wound Secondary Couplings In The Nonlinear Region Of The Magnetization Curve

This paper presents an analytical treatment to compute the torque-speed curve of a dc excited electromagnetic coupling considering magnetic saturation. The complete nonlinear magnetization curve is mathematically represented and the maximum torque is accurately predicted. The above approach being a generalized one can be applied to any electromagnetic apparatus working under saturation condition. The present coupling can also be used as a variable speed drive.

An electromagnetic flowmeter for simultaneous measurements of pulmonary arterial and aortic blood flows in the conscious animal

An electromagnetic flowmeter apparatus for simultaneous measurements of pulmonary arterial and aortic blood flows in the conscious animal is described. The apparatus retains the basic features of the sine wave flowmeter and coreless flow transducers developed byKolin and provides for recordings from two adjacent transducers. The proximity of the implanted transducers results in a constant interaction which alters the techniques for calibration and zero flow determination which have been reported for single-flow measurements. The apparatus has linear frequency and phase shift characteristic to ensure undistorted flow measurement up to 50 c/s.

A simplified electromagnetic apparatus for use in undergraduate teaching

A simplified electromagnetic apparatus for use in undergraduate teaching

The rotating electric machine in an electrical engineering degree course

A discussion is presented of how best to utilize the dwindling portion of the engineering curriculum devoted to the rotating machine. A course of study of electromagnetism is outlined in which the rotating electric machine is treated as a separate topic rather than as part of a unified approach to all electromagnetic apparatus.

An electromagnetic apparatus with a high resolving power for the separation of the isotopes of the heavy elements

The operating principles and the main features of an electromagnetic apparatus which has been designed and constructed for the separation of isotopes with a relative mass difference of about 1/240 are here described. An axially-symmetric magnetic field is used (focussing angle 225 °) in which the dispersion is proportional to the square of the focussing angle. The dispersion obtained with the separation apparatus is 20 mm for a 1% relative difference in mass. The magnetic field of the apparatus is stabilized to within 0.005% with the help of a circuit containing electron-beam regulators. Ion sources, with a discharge in the vapor of the working and auxiliary substances, were developed for the separation of large and small quantities of the raw material. General-purpose ion collectors were also developed. Some results of the separation of lead, uranium and plutonium isotopes are given. The enrichment factor in the separation of lead isotopes reaches 300, while for uranium and plutonium it is ∼ 1000.

The ballistocardiogram in coarctation of the aorta

1. 1. Eighteen cases of coarctation of the aorta have been studied. All showed absent or short K waves in the photoelectric tracings. I waves were also deep in fifteen patients. Electromagnetic tracings were found to be normal in three of the eighteen cases. 2. 2. Photoelectric (displacement) apparatus displays the abnormalities of coarctation of the aorta more obviously and strikingly than the electromagnetic (velocity) apparatus. 3. 3. Absent or short K waves seem to be a constant ballistocardiographic finding in coarctation of the aorta when photoelectric tracings are recorded. 4. 4. In the presence of hypertension, the above-mentioned ballistocardi-ographic findings are suggestive of aortic coarctation. 5. 5. No correlation was seen between the degree of hypertension in the upper extremities and the degree of the ballistocardiographic abnormalities. 6. 6. The results of this study indicate that the simple direct-body ballistocardiographs show abnormalities in coarctation of the aorta as clearly as those obtained by the other complicated table-model apparatus.

Transactions section: Preprint of corresponding pages from the current annual AIEE transactions volume: Dynamic measurements on electromagnetic devices

FOR the investigation of relays and similar electromagnetic apparatus, data giving the variation of current and flux as well as the motion of the armature during the operating cycle are of great value. The rapid-record oscillograph <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> has been used extensively for current measurements and, where a moderate accuracy is sufficient, is very satisfactory. Data on the flux also may be obtained by graphical integration of oscillographic data, but such a process is laborious and, unless great care is taken, is of doubtful accuracy. The development of a shadow-graph attachment <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for the oscillograph provided a means of measuring armature motion at the same time and with the same order of accuracy as the current measurements.

Some polarization phenomena in magnetic materials, with special reference to nickel-iron alloys

Asymmetry of E-I loops for nickel-iron cores under alternating magnetizing forces is shown to be due to residual polarization, the distribution of which throughout the crosssection of the stamping is different from the distribution of the flux due to the applied alternating magnetizing force. It is also shown that such polarization may, under certain conditions, bein different directions simultaneously in the inner and outer parts of thestamping. The polarization can be removed by applying a relatively large alternating magnetizing force and reducing it slowly to zero. Curves are produced showing the amount of polarizing flux removed by different values of alternating magnetizing force, tarting with a known value of residual flux. It is shown that in the case of mumetal the curves are different when the residual flux is caused by switching off alternating and direct current respectively. Other curves show the marked increase in polarizing flux produced bydirect current when an alternating magnetizing force of suitable valueis superimposed. The reduction of apparent permeability due to residual polarization is also shown. Strong polarization is found to occur, both in nickel-iron and in silicon-steel cores, under conditions in which capacitanceloading of the secondary winding produces resonance with even harmouics, provideda small initial polarization is present. Initial polarization sufficient toallow this phenomenon to occur is found to be usually present, evenwhen thenormal loop is almost symmetrical. The presence of even harmonics in the magnetizing current, as may occur, for instance, when the source of supply iathermionic valve, is also found to cause polarization. With certain values of capacitance loading of polarized specimens, sub-harmonics are produced. The asymmetry of E-I loops or specimens with residual polarization is found to be less apparent as the frequency is raised above 50 cycles per sec. It is pointed out that these phenomena should be taken into account in the design and operation of electromagnetic apparatus, but that cores of the more usual commercial forms will not exhibit the phenomena to the same extent as the plain ring stampings used in most of the tests described.