Single-layer Coil Research Articles

A pulsed field magnetometer for the characterization of hard magnetic materials

A pulsed-field magnetometer is described that can be used for measuring the hysteresis of hard magnetic materials and also for determining the anisotropy field. The magnetometer operates at room temperature with a maximum field of approximately 12 MA/m. Special emphasis was given to the analysis of the measuring system. The conditions for optimizing a single-layer pick-up coil are calculated. For elliptically shaped particles, the signal is no longer proportional to the mass of the particle. The sensitivity of a single-layer coil increases first with the number of turns of wire (N), saturating for larger N values. The most sensitive coil is achieved when N is equal to the diameter of the wire used. The pick-up signal is calculated for samples with spherical, cylindrical, and elliptical shapes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Cross-Axis Synchronous Flow-Through Coil Planet Centrifuge Free of Rotary Seals for Preparative Countercurrent Chromatography. Part II. Studies on Phase Distribution and Partition Efficiency in Coaxial Coils

Abstract Potential capability of the apparatus in performing countercurrent chroma-tography has been examined with three different types of coiled columns, all coaxially mounted around the holder. In single-layer coils, typical solvent systems display characteristic hydrodynamic distribution which ensures a stable retention of the stationary phase against heavy sample loading in preparative separations. Direct observation of the hydrodynamic motion in the rotating spiral column revealed vigorous mixing of the two solvent phases throughout the area which promises a high partition efficiency of the present method. Gram-quantity preparative separations were performed in the multilayer coil with two different sets of test samples: Isocratic elution of dinitrophenyl amino acids yielded high partition efficiency of 1600 theoretical plates while the versatility of the method was demonstrated on gradient elution of dipeptides including two pairs of sequential isomers.

Inductance formula for a single-layer circular coil

The analytical formulas for the self-inductance of a cylindrical current sheet (solenoid of any size) and the mutual inductance of two coaxial current loops are presented. A simple iteration method for evaluating the formulas to any desired degree of accuracy is also discussed.

Window Frame or "Superferric" Magnet Design for Low B(&lt;3t) Heavy Ion Storage Ring Study

Double magnets share common laminations without magnetic coupling. Single layer coils of rectangular conductor are dry wound on extruded bore tubes. Magnet construction requires no molding or prestress. Absence of superconducting (SC) magnetization fields in the aperture results in very large dynamic range. The coil is wound continuously across the midplane to give unusually large dynamic aperture. Above ~2.2 T saturation is corrected by simple sextupole windings with no inductive coupling to the dipole. Ultrastable design requires no internal quench protection. A quadrupole pair of novel design gives excellent field quality to B > 2 T without corrections, with no SC magnetization. Experience shows magnets are accurate enough for the assembly to take place at its final location. No training is required. Test procedures (measurements with search coils or with the beam) and cooldown properties are discussed.

Nb&amp;lt;inf&amp;gt;3&amp;lt;/inf&amp;gt;Sn-composite conductors with Aluminum as electrical stabilizer and stainless steel as mechanical reinforcement

Three-component conductors composed of a preheat-treated Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn flat cable, aluminium, and stainless steel were soldered together in a straight alignment and then wound in a single-layer coil with a diameter of 90 mm. The performance of the composite conductor was determined mainly by the position of the steel, because the steel shifts the neutral plane considerably due to its high modulus of elasticity and can generate high compressive forces on the Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn with a consequent reduction of critical current density. The aluminum stabilizer developed its full stabilizing performance only in close contact with the superconductor, because resistive layers between them cause partial resistivity in the superconductor.

Constant tension winding in a single layer rippled solenoids

The forces on a rippled single layer coil are exactly calculated. The ripple shape is changed in a series of iterations to arrive at constant tension zero bending shape. Analytical expressions and numerical methods are included.

On calculating losses in current carrying conductors in an external alternating magnetic field

A common approach in calculating ac resistance is to add together losses due to a magnetically isolated conductor and the losses due to eddy currents induced in the same conductor by an externally excited magnetic field in the absence of primary conductor current. This method is employed in the design of large current carrying devices such as multiphase cables and reactive elements. The present analysis shows that this "superposition" method for calculating ac resistance is an approximation which is valid only under restrictive conditions. This is illustrated by calculating the total joulean losses in a single layer coil in Cartesian coordinates and identifying the contributions due to the primary coil current and eddy currents induced by the external field.

Butterfly-valve inductive orientation detector

Relative changes of inductance ΔL/L of a single layer coil surrounding a thin electrically conducting disk which can rotate about an axis perpendicular to the coil axis are studied experimentally as a means of measuring angular displacements. ΔL/L is found to be a strong function of disk diameter and is weakly dependent on the ratio of disk thickness to electromagnetic skin depth when this ratio is of the order unity. Values of ΔL/L as a function of disk diameter are given for lead, brass and copper. Detection sensitivities using a resonant tank circuit or an astatic transformer are given in terms of ΔL/L and it is shown that sensitivities of the order of 10−3 to 10−4 deg are practical. Application of this system to the Rayleigh disk and cryogenic environments are emphasized and an expression for the magnetic torque due to detection currents is given.

Explosion-magnetic generator with a plasma load

primary winding of the matching transformer. The initial EMG inductance was Lo = 1.9 ~H, the solenoid inductance was L, = 65 ~H, and the weight of the explosive charge was 2.5 kg. The EMG power was identical in all the tests (Wo = 60  5 kJ). The secondary winding of the matching transformer was a 7-turn single-layer coil wound from copper ribbon of 40  1.5 mm section on a dielectric carcass. The coupling coefficient between the solenoid and the EMG was k = 0.9-0.95. The load was connected to the secondary winding by 20 parallel 6-m-long FPK cables. The total inductance of the secondary loop, including the transformer winding L2 = 3.2 ~H, the cable L c = 0.3 ~H, and the load L L = 0.I0.5 ~H, was approximately identical in all the tests and equalled L = L2 + L c + L L = 3.64.0 ~H, and only the active load resistance changed. The discharge was initiated in normal density air by the electrical explosion of a differently sized foil. An erosion type discharge between coaxial electrodes separated by a dielectric was used as EMG load at a 10 -2 mm Hg pressure. The change in load resistance was achieved by varying the geometric dimensions of the foil and the number of discharge gaps. Aluminum foil 0.02 mm thick, of the areas 20  i0; 40  15; 80  15 cm with an initial resistance of 3.0, 4.0, 8.0.10 -3 ~, respectively, was used. The foil was pressed between flat electrodes with reverse leads in the form of a double symmetric frame form a 10-cm-wide copper strip. The loop symmetry achieved in this manner relative to the foil permitted equilibrating the ponderomotive repulsion forces acting on it by oppositely directed currents. The inductance of the frame with the foll was 0.33, 0.33 and 0.49 ~H, respectively, for the above-mentioned foil sizes. The currents and voltages in the EMG power loops and in the load were determined by using Rogovskii belts and ohmic dividers in the tests; the magnetic field intensity in the solenoid was measured by an inductive transducer; the spectral fluxes and the discharge radiation energy in the visible and infrared spectrum ranges were recorded by photodiodes.

The accurate computation of forces between circular coils

A new approach for the computation of the forces between coaxial single-layer coils is introduced. It is based on the direct application of Bartky's transformation to the basic force expression in terms of the axial derivative of the mutual inductance. Differentiation and integeration in the axial direction are done analytically and the transformation is applied successively to reduce the integrand to a form that can be analytically integrated in the angular direction. The iterative process is fast and simple and can yield results to any specified accuracy. The algorithm is applicable over the entire range of coil sizes, shapes and degrees of coupling. It extends an earlier algorithm that has been developed for the computation of inductances. The new algorithm has been checked over the whole range against the numerous results available in the literature. The accuracy of the results is only limited by the word length of the computer used and the loss in significant figures incurred in the computations is usually less than three. In the extreme cases, Grover's tables were found to be correct to one significant figure only.

Uniformity condition for a rectangular field coil with a split winding

A generalized Helmholtz condition for field uniformity is derived from the closed form solution of the magnetic field in a multilayer rectangular coil pair as a function of coil dimensions and pair separation. The relation among the dimensions satisfying this condition is found and plotted in parametric form for single layer coils and for a multilayer coil with a specific winding thickness. For square coils of cross section small compared to their mean radius, the gap separation approaches half the coil radius, analogous to the classical condition for circular coils. Comparison between theoretical and measured values for tolerances within +/-5% of the field at the system center agree within a 6% maximum deviation. For the experimental coil, the area enclosed by the +/-5% contour was 58% of the area of the full coil.

Eine Methode zur Bestimmung des Widerstandswertes aus der Induktivität

A combined Maxwell Series resonance bridge is used to determine the unit of resistance in terms of the unit of inductance. A calculable single-layer coil is used as a standard of inductance. Only one capacitor, which has to be stable but not exactly known, is switched from one bridge arm to the other. The time constants of the resistors as well as the distributed and stray capacities of the coil are measured separately and taken into account when evaluating the bridge equation. Experimental results with frequencies of 225 and 317 Hz show that the error limits of the electrical measurements do not exceed 0.5 ppm.

Automatic methods in radio component manufacture

Part 1 describes a method of controlling a high-speed coil winder by an electronic counter. A specialized machine which winds single-layer coils is described.Part 2. deals with the development of a tool protection device for use with automatically loaded presses. The device detects the piece-part magnetically as it is ejected and so clears the interlocks to allow the press to continue operating.

Determination of Voltage, Current, and Mlagnetic Field Distributions Together with the Self-Capacitance, Inductance and HF Resistance of Single-Layer Coils

A theoretical investigation for quantitative evaluation of voltage, current, and magnetic field distribution along single-layer coils is presented herein. The magnitudes and the number of harmonics present in the distribution are obtained for the first time. From the voltage and current distributions, the self-capacitance and inductance of coils have been obtained. The self-capacitance depends mostly on the length to diameter ratio; it slightly depends on the amount of harmonics as well as the pitch to wire-diameter ratio. The harmonics mainly rely on the number of turns, the operating frequency, the coil diameter, and the length to diameter ratio. From the magnetic field distribution, the HF coil resistance is obtained. Experimental results extracted from previous authors are in good agreement with the theoretical predictions.

The resistance of round-wire single-layer inductance coils

The resistance of round-wire single-layer inductance coils

The resistance of round-wire single-layer inductance coils

Butterworth's two formulae for the resistance of short coils with a finite number of turns and long coils with an infinite number of turns are merged into a single formula valid for coils of any length and having any number of turns. Numerical values of the functions appearing in the formula are given in tables. The formula is shown to give results in reasonable agreement with the experimental figures of Medhurst and Hickman.

High-Impedance Cable

A cable with an impedance of the order of 1000 ohms is described. It resembles the usual flexible concentric cable with a 3/8-inch outside diameter, but its inner conductor is a single-layer coil continuously wound on a flexible core of 0.110-inch diameter. The cable is suitable for video connections from chassis to chassis and to remote indicators.

Electromagnetic Waves in Transformer Coils Treated by Maxwell's Equations

A rigorous solution of Maxwell's equations is derived for waves in a thin single-layer coil, a concentric ground electrode being at a short distance from the coil. Simple transformer coils resemble such an ideal to a considerable degree. Any electromagnetic state of the coil propagates slowly in axial direction with such a velocity that the phase velocity along the helical conductor equals the velocity of light. The surge impedance of the coil is constant for low frequency, but decreases with higher frequency, the boundary wave-length being determined by the insulating distances.

Torque between concentric single-layer coils

Torque between concentric single-layer coils

LXIV.The self-capacitance of single-layer coils

Summary The self-capacitance of a series of air.. dielectric single-layer solenoids of 2, 3, and 4 inches diameter, and of length to diameter ratio extending from 0.25 to 4.1, has been determined from measurements of the natural frequency and by immersion in a liquid of known dielectric constant. It is shown that the self-capacitance is independent of frequency, and that the self-capacitance to radius ratio is independent of the radius for a given coil-shape. The results are compared with existing theories. A study has also been made of the effect of end-connexions, wire diameter, wire covering, and of the presence of a coil former on the effective self-capacitance. Finally, mention is made of a few measurements on 2- and 3-1ayer coils.