Coil Gap Research Articles

心臓ペースメーカー用経皮的電力伝送コイルの設計に関する考察

Ordinarily whenever the battery is drained, the entire implanted device using the battery is changed. It is possible to extend the life of an implanted device by using a primary battery plus a secondary rechargeable battery. For example, a rechargeable cardiac pacemaker is covered with a titanium case. The secondary rechargeable battery is charged from the outside of the body. The titanium case, however, has a negative effect on transmission efficiency. In this study, we designed transmission coils considering circuit parameters and coil shapes. The proposed secondary coil is located within the inner wall of the titanium case. The primary coil has a spiral shape, with a constant outside diameter of 80 mm. We compared transmission efficiency for various inside diameters. The experiment results, we show that when the secondary coil is covered with a titanium case, the best inside diameter for the primary coil is 28 mm. If the coil gap is 20 mm, the transmission efficiency is 22%.

海中におけるＣＬＰＳ給電に関する基礎的検討

A contactless power station (CLPS) with cone-type coils is proposed for use in the sea. The cone-type coils are used in order to keep the efficiency high by means of dislocation. It was confirmed that the power transmission characteristics in the sea agreed well with those in the air. The mutual inductance and self-inductance were calculated by using Neumann’s formula, which involves by the diameters of the coils, the number of turns and the coil gap. It was confirmed that the calculated values agreed well with the experimental values. The relation between the coupling factor and the ratio of the coil diameter and the coil gap was discovered, and the coil was designed for the optimum load.

Contactless heating of moving wires

A novel method is described for uniform radio frequency (RF) heating of static or moving wires at atmospheric pressure, over long lengths, without the use of contacts or brushes. Conventional induction heating of wires is not possible because of the large annular coil gap and the RF skin effect if the wire diameter is comparable to the skin thickness. The method described involves placing a rod, of length equal to the heated zone required, parallel to the wire to be heated and about 2 cm from it, which allows the wire to be enclosed in a glass tube containing a protective atmosphere if required. The rod is connected to a 13.56 MHz RF power source. Heated wire lengths tested ranged from 1 mm to 70 cm, and no indication was found of an upper limit of heated length. No special tuned length of wire is required and there is no upper limit to the temperature obtainable. The temperature along the wire can be either uniform or a temperature gradient can be set up by bending the RF rod closer to or further from the wire in a local region. A simple RF safety screen of 2 cm wire mesh size was found to prevent RF emission to the operator and environment. The method is of interest in wire processing and in chemical vapour deposition of coatings on wires, including insulating coatings, etc. The alternative method of resistive heating with physical contacts may cause surface damage and sparking and does not allow optional controlled temperature gradients along the wire, nor heating at all if there is an insulating coating.

Development of a 7 tesla superconducting wiggler

A 7 T three poles superconducting wiggler has been constructed to be used as a light source in AURORA-2D, a 700 MeV compact SR ring. The wiggler is cooled by compact Gifford-McMahon cryocoolers without liquid helium. The main components of the wiggler are three pairs of racetrack superconducting coils in an iron yoke, bismuth based oxide superconducting current lead unit and Gifford-McMahon cryocoolers. The coils generate a magnetic field of 7 T in a 40 mm coil gap within 360 seconds. The magnetic field period along the electron beam of the SR ring is 342 mm. The magnetic field integral is less than 4/spl times/10/sup -4/ Tm. The coils and the yoke are cooled by a Gifford-McMahon cryocooler with Joule-Thomson valve. The current lead unit and the thermal shield plate are cooled by separate Gifford-McMahon cryocoolers without Joule-Thomson valves. The current lead unit is designed to be easily removed for maintenance. The performance test in AURORA-2D was successfully completed. The maximum beam current was 19 mA at 700 MeV.

Flow-through air-cooled loudspeaker system

The loudspeaker and enclosure are provided with aerodynamically-shaped passages providing low-pressure regions for inducing flows of air into and about the driver motor of the loudspeaker in response to vibratory movement of the speaker cone. An aerodynamically-shaped body is disposed within the pole piece to define a venturi passage for exchange of air between an interior chamber defined by a coil former and the back of the speaker. Aerodynamically-shaped openings are provided through the pole piece for inducing flow of air about the voice coil in the voice coil gap between the pole piece and permanent magnet. The speaker frame support is provided with aerodynamically-shaped openings to induce air flow into the interior chamber. In this manner, low-pressure regions established by the aerodynamic shapes induce flow of cooling air about the voice coil and pole piece in response to vibratory movement of the cone. Aerodynamic shapes are disposed in the intake and exhaust vents of the speaker enclosure to exchange air between the enclosure and atmosphere in response to vibratory movement of the speaker.

Damping effects of magnetic fluids of various saturation magnetization (abstract)

Magnetic fluids have been widely accepted for use in loudspeaker voice coil gaps as viscous dampers and liquid coolants. When applied properly to a voice coil in manufacturing of the loudspeaker, dramatic improvement in frequency response and power handling is observed. Over the past decade, a great deal of study has been given to the effects of damping as a function of fluid viscosity. It is known that the apparent viscosity of a magnetic fluid increases as a function of applied magnetic field, and that the viscosity versus field relationship approximate that of the magnetization versus applied field. At applied magnetic field strength sufficient to cause magnetic saturation of the fluid, no further increase in viscosity with increased magnetic field is observed. In order to provide a better understanding of the second order magnetoviscous damping effects in magnetic fluids used in voice coils and to provide a better loudspeaker design criterion using magnetic fluids, we have studied the effect on damping of several magnetic fluids of the same O field viscosity and of varying saturation magnetization. Magnetic fluids with saturation magnetization ranging from 50 to 450 G and 100 cps viscosity at O applied field were injected into the voice coil gap of a standard midrange loudspeaker. The frequency response over the entire dynamic range of the speaker was measured. The changes in frequency response versus fluid magnetization are reported.

Horn speaker and method for producing low-distortion sound

An acoustical horn speaker for producing low distortion sound comprised of a casing assembly having a voice coil gap and a magnetic source and return circuit for providing a constant magnetic field across the gap, a current-carrying voice coil disposed in said gap, and a voice diaphragm in rigid attachment with the voice coil, said voice diaphragm being suspended from the casing assembly by a relatively flexible, high compliance suspension member. An acoustical horn having a throat resistance sufficiently high to substantially dominate the radiation resistance of the diaphragm is air coupled at its throat end to the voice diaphragm suspended from said casing, while the compliance of the voice diaphragm suspension is relatively high such that in the presence of the dominating throat resistance of the horn the diaphragm vibratory movement is characterized by substantially force determinative excursions as opposed to substantially linear constant displacement excursions. A method of producing low distortion sound in a horn type speaker comprising the step of driving the speaker's diaphragm in a vibratory movement characterized by substantially force determinative excursions as opposed to substantially linear constant displacement excursions.

The effects of high voltage tesla coil and spark gap discharges on the track registration properties of some plastic track detectors

Abstract Experiments have been carried out to study the role of radiations produced in the discharge of (a) Tesla Coil, and (b) Spark Gap, in the enhancement of the latent damage existing in the plastic track detectors. It has been found that the revelation of the damage trails is affected by the high voltage sparks. Plasma generated ultra-violet rays, electrons and ozone might be responsible for the sensitization.