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Showing papers on "Electromagnetic coil published in 1989"


Patent
Kozo Satoh1
29 Aug 1989
TL;DR: In this article, a magnetic resonance imaging system includes a magnetic field applying section for applying a static field, gradient field pulses and an RF field to an object to be examined, a signal detecting section, including a homogeneous coil and a plurality of surface coils arranged to surround a desired region of the object, for detecting magnetic resonance signals from the object through the homogeneous coils and the surface coils, and an image data processing section for obtaining an image of the desired region by synthesizing image data based on the magnetic resonance signal respectively detected by the surface coil upon weighting/adding processing
Abstract: A magnetic resonance imaging system includes a magnetic field applying section for applying a static field, gradient field pulses, and an RF field to an object to be examined, a signal detecting section, including a homogeneous coil and a plurality of surface coils arranged to surround a desired region of the object, for detecting magnetic resonance signals from the object through the homogeneous coil and the surface coils, and an image data processing section for obtaining an image of the desired region by synthesizing image data based on the magnetic resonance signals respectively detected by the surface coils upon weighting/adding processing. The system uses differential surface coils as the surface coils. A magnetic resonance signal is detected through the homogeneous coil within the same time interval in which magnetic resonance signals are detected through the surface coils. Weighting functions for weighting/adding processing of image data are determined on the basis of these magnetic resonance signals.

305 citations


Patent
13 Sep 1989
TL;DR: In this article, a method and apparatus for determining accurately the location of the tip of a catheter inside biological tissue is disclosed including a locator (34) having a coil (38) wound axially on a core (36) and a detector (12) in the form of a coil(28) wound on the core (24) removably positionable within catheter (16) adjacent the tip.
Abstract: A method and apparatus (10) for determining accurately the location of the tip (14) of a catheter (16) inside biological tissue is disclosed including a locator (34) having a coil (38) wound axially on a core (36) and a detector (12) in the form of a coil (28) wound on a core (24) removably positionable within catheter (16) adjacent the tip (14). A controller (20) generates AC current to coil (38) to produce an electromagnetic field and compares it with the output voltage developed in coil (28) when the locator (34) comes within close physical proximity to detector (12). Locator (34) includes an amber LED indicator (42) which is energized when the locator (34) is behind the detector (12) and the monitored output voltage is in phase with the generated alternating current and includes a red LED indicator (44) which is energized when the locator (34) is beyond the detector (12) and the monitored output voltage is 180° out of phase with the generated alternating current. The controller (20) includes a beeper (48) which provides an audible indicator when energization changes between the indicators (42, 44).

249 citations


Patent
19 May 1989
TL;DR: In this paper, an elastic memory was used to expand the coil stent into contact with the inner walls of the vessel and to the diameter substantially greater than the predetermined diameter, allowing the stent to return to the given diameter after any distortion.
Abstract: A method for preventing arterial restenosis after angioplasty and including the steps of providing from a plastic material filament a base coil of a substantially uniform given diameter, inducing in the base coil an elastic memory that provides an inherent tendency thereof to return to the given diameter after any distortion, forming from the base coil a coil stent with a substantially uniform predetermined diameter substantially less than the given diameter, releasably coupling the coil stent to an elongated delivery device adapted to pass through a blood carrying vessel, inserting the coil stent and delivery device into a vessel, and manipulating the delivery device within the vessel so as to position the coil stent at a desired location therein. After placement, the coil stent is decoupled from the delivery device which is removed from the vessel, and the elastic memory is allowed to expand the coil stent into contact with the inner walls of the vessel and to the diameter substantially greater than the predetermined diameter. The use of an inherently expandable plastic coil stent permits the effective prevention of restenosis in small arteries typically found in the area of the heart.

233 citations


Journal ArticleDOI
TL;DR: An endorectal surface coil has been developed to obtain high-resolution magnetic resonance images of the prostate that better demonstrate prostatic anatomy and pathologic conditions.
Abstract: An endorectal surface coil has been developed to obtain high-resolution magnetic resonance images of the prostate. The probe consists of a surface coil mounted on the inner surface of a balloon. The balloon is concave to ensure tight seating against the prostate. The coil has been used in 15 patients with biopsy-proved prostatic carcinoma and in two healthy volunteers. The axial images were obtained with a 12-16-cm field of view and a 3-mm section thickness. Compared with images obtained with a body coil, the surface coil images better demonstrate prostatic anatomy and pathologic conditions.

218 citations


Patent
02 Jun 1989
TL;DR: In this article, a rectilinear motion proportional solenoid assembly includes a cylindrical housing containing an electromagnetic coil having a longitudinal coaxial bore, which contains maagnetic material for providing a flux path for the magnetic field produced by the coil.
Abstract: A rectilinear motion proportional solenoid assembly includes a cylindrical housing containing an electromagnetic coil having a longitudinal coaxial bore. The housing contains maagnetic material for providing a flux path for the magnetic field produced by the coil. A generally cylindrical magnetic pole piece element is inserted into the bore and a movable armature assembly of magnetic material is supported within the bore for movement along the longitudinal axis of the coil by a pair of thin, flexible suspension springs. One of the springs is located within the bore adjacent to one end of the magnetic pole piece whereat an axial gap between the pole piece and the armature is formed. A second spring is located within the housing within the vicinity of a radial air gap between the armature and the housing. The pole piece contains an auxiliary region adjacent to the axial air gap for shunting a portion of the axially directed magnetic flux, for effectively causing the force imparted to the movable armature by the application of a current to the electromagnetic coil to be substantially constant irrespective of the magnitude of the axial gap for a variation in the axial gap over a prescribed range.

186 citations


Journal ArticleDOI
M. Morishita1, T. Azukizawa1, S. Kanda, N. Tamura, T. Yokoyama 
TL;DR: In this article, a power-saving electromagnetic suspension system was developed in which electromagnets with permanent magnets were used to suspend the vehicle and the electromagnetic coil current required to keep a vehicle levitating was extremely small, ideally zero.
Abstract: A power-saving electromagnetic suspension system has been developed in which electromagnets with permanent magnets are used to suspend the vehicle. The electromagnets are controlled to maintain air gap length so that the attractive force by the permanent magnet always balances the total weight of the vehicle and its loads, based on modern control theory. This technology realizes a significantly power-saving system in which the electromagnetic coil current required to keep a vehicle levitating was extremely small, ideally zero. The 8-kg weight test vehicle with 4-kg load could be levitated continuously over 8 h, without recharging the on-board 1300-mAh batteries. This technology realized a completely contact-free material transportation system when combined with a contact-free driving system using linear motors. The attractive force characteristics of a permanent magnet with control electromagnets and the newly developed electromagnet control system that can eliminate power collecting devices from the electromagnetic suspension system are described. >

158 citations


Patent
18 May 1989
TL;DR: In this paper, a guiding member for vascular catheters, particularly dilatation catheter for angioplasty procedures having a deflectable tip, is described, where the core wire is secured to the coil at a location distally of the expanded section but proximally to the distal tip of the coil.
Abstract: The invention is directed to a guiding member for vascular catheters, particularly dilatation catheters for angioplasty procedures having a deflectable tip. The guiding member generally includes an elongated core wire (11) having a tapered distal portion (14), a coil (13) encasing at least part of the tapered distal portion of a core wire. The coil has an expanded section (16), and a reference member (18) disposed therein which is secured to the coil proximally and distally of the expanded coil section. The core wire is secured to the coil at a location distally of the expanded section but proximally to the distal tip of the coil. Relative axial movement between the core wire and the coil causes expansion or contraction of the expanded coil section which results in tip deflection.

153 citations


Patent
30 Aug 1989
TL;DR: In this paper, a transponder is configured to self resonate at the operating frequency of the identification circuit when brought within range of an interrogator's magnetic field, thereby creating a voltage across the primary coil having a high source impedance.
Abstract: A coil assembly for use in an inductively powered transponder including a primary coil and a secondary coil wrapped around the same coil forming ferrite rod. The primary coil's leads are left floating while the secondary coil's leads are connected to the integrated identification circuit of the transponder. There are approximately three times as many turns to the primary coil as there are turns to the secondary coil. The primary coil is configured to self resonate at the operating frequency of the identification circuit when brought within range of an interrogator's magnetic field, thereby creating a voltage across the primary coil having a high source impedance. The secondary coil is configured to resonate at the same operating frequency, but to convert the high source impedance level of the primary coil to a low source impedance level, which is more suitable for powering the identification circuit and which substantially matches the impedance level of the secondary coil to the impedance level of the interrogator field, thereby maximizing the quantity of energy which can be transferred between the interrogator and the transponder.

150 citations


Journal ArticleDOI
TL;DR: In this paper, a coreless design appropriate for use with high energy permanent magnets is proposed which would significantly reduce the weight of the units, and the results indicate that for the oscillation freauencies tvoicallv encountered in road vehicle suspensions, electrodynamic variable shock absorbers are feasible.
Abstract: SUMMARY Linear electrodynamic motors consisting of coils of copper wire interacting with magnetic fields produced by permanent magnets can be used to construct mechanical dampers with a damping coefficient which can be rapidly varied by changing the external resistance connected to the coil. Limitations to the use of these variable dampers arise due to the coil's own resistance and mass and the practically achievable magnetic field. A moving coil system is first analyzed and then modifications to the basic results when a moving magnet design is used are given. The results indicate that for the oscillation freauencies tvoicallv encountered in road vehicle suspensions, electrodynamic variable shock absorbers are feasible. A novel coreless design appropriate for use with high energy permanent magnets is proposed which would significantly reduce the weight of the units.

150 citations


Patent
22 Sep 1989
TL;DR: In this article, a guide wire assembly comprising a flexible guide wire having a diameter of 0.018 inches or less and having a connector assembly is described, and the connector assembly includes male and female connectors.
Abstract: A guide wire assembly comprising a flexible guide wire having a diameter of 0.018 inches or less and having a connector assembly. The connector assembly includes male and female connectors. The male connector includes a conductive coil spring and a core wire which extends beyond the conductive coil. The female connector includes a recess for receiving the core wire as well as a conductive element for engaging the coil spring.

122 citations


Patent
22 Nov 1989
TL;DR: An epidural catheter is disclosed having a durable and a flexible segment joined together as mentioned in this paper, which is inserted into a patient with the use of a well-known needle which is removed by passing the needle over the outside of the catheter.
Abstract: An epidural catheter is disclosed having a durable and a flexible segment joined together. The flexible segment is inserted into a patient with the use of a well-known needle which is removed by passing the needle over the outside of the catheter. The flexible segment is atraumatic to the surrounding tissue. The flexible segment includes a plastic tube surrounded by a wire coil for pushing the tube into a passageway of the tissue. The distal end of the plastic tube and wire coil are joined to prevent unwinding of the coil when extracted. The tightly coupled wire coil also permits the flexible portion to be easily inserted into the passageway of the tissue. The durable segment joined to the flexible segment includes a stainless steel tube with a flat wire coil surrounding a length of the tube. The stainless steel tube permits fluid at an elevated pressure to pass through the hollow passageway therein without rupturing. The flat wire coil prevents kinking of the semi-rigid stainless steel tube. When a fluid at an elevated pressure is received, the distal end of the flexible tube is closed to diffuse the fluid passing through the length of the catheter. Slits are provided laterally on the side of the plastic tube for emitting and diffusing the fluid through the wire coil.

Patent
20 Oct 1989
TL;DR: In this paper, a tunable inductor in series with the piezoelectric crystal excitation transducer in the probe which has a flux modulation coil is controlled by the system.
Abstract: The system uses a tunable inductor in series with the piezoelectric crystal excitation transducer in the probe which has a flux modulation coil. The bias current through this flux modulation coil is controlled by the system. It is controlled such that the inductance of the tunable inductor cancels out the capacitive reactance of the load impedance presented by the probe when the probe is being driven by a driving signal which matches the mechanical resonance frequency of the probe. The resulting overall load impedance is substantially purely resistive. The system measures the phase angle and monitors the power level. The system uses this information to adjust the bias current flowing through the flux modulation coil to maintain the substantially purely resistive load impedance for changing power levels. This information is also used to adjust the frequency of the driving signal to track changing mechanical resonance conditions for the probe at different power levels. This method of operation insures substantially maximum power transfer efficiency and substantially linear power control over a range of power dissipation levels. There is also disclosed an analog circuit to measure the phase angle for the load driving signal and to adjust the frequency of the driving signal for best performance. This system includes an integrator to eliminate the effect of offset errors caused by operational amplifiers. There is also disclosed a system to determine the mechanical resonance frequency by sweeping the drive frequency and monitoring the drive current for the frequency at which the drive current is a maximum.

Journal ArticleDOI
01 Sep 1989
TL;DR: In this paper, a frequency-dependent impedance formula, derived on the assumption of a solid homogeneous core, may be adapted to permit calculation of the self and mutual impedances of coil sections on a practical transformer core.
Abstract: The paper shows how a new frequency-dependent impedance formula, derived on the assumption of a solid homogeneous core, may be adapted to permit calculation of the self and mutual impedances of coil sections on a practical transformer core. Experimental measurements, in comparison with calculated values, show that the effects of the laminations can be accurately simulated by using two distinct resistivities in different parts of the basic formula. A method is given for determining these quantities experimentally. Application of the resulting formula in transient analysis automatically accounts for the effects of transient flux penetration into the transformer core, including the effects of frequency-dependent inductances and transient eddy currents in the core laminations.

Patent
01 Sep 1989
TL;DR: A magnetic resonance (MR) imaging system includes a magnet for producing a magnetic field to which a patient is subjected, a radio frequency (RF) transmitter coupled to a body coil within the magnet and placed as close as possible to tissue being analyzed by the MR imaging system, and a computer controlled system for generating RF signals from the transmitter and detected by the receiver for use in producing nuclear excitation and corresponding detected induced currents in the surface coil sent to an analog-to-digital converter and then to the computer for processing into an image display of the tissue under analysis.
Abstract: A magnetic resonance (MR) imaging system includes a magnet for producing a magnetic field to which a patient is subjected, a radio frequency (RF) transmitter coupled to a body coil within the magnet, an RF receiver coupled to a surface coil within the magnet and placed as close as possible to tissue being analyzed by the MR imaging system, and a computer controlled system for generating RF signals sent from the transmitter and detected by the receiver for use in producing nuclear excitation and corresponding detected induced currents in the surface coil sent to an analog-to-digital converter and then to the computer for processing into an image display of the tissue under analysis. A preferred embodiment of the invention comprises surface coil apparatus for use in analyzing tissue within a body cavity of the patient, and a preferred system for use in analyzing the tissue of the prostate gland includes an elongated hollow tube for transrectal insertion, and expandable balloon sealed to the exterior of the tube, and a loop antenna surface coil wire secured to the exterior wall of the balloon. Fluid pressure applied to the inside of the tube and then to the interior of the balloon expands the balloon and thereby expands opposite sides of the surface coil wire and holds the surface coil antenna in a spaced apart expanded position useful in serving as a means for obtaining high resolution imaging of prostatic tissue.

Patent
04 Feb 1989
TL;DR: In this article, a device for the transmission and evaluation of measurement signals for the tire pressure of tubless tires mounted rims in single and twin wheels of motor vehicles is presented, which comprises a pressure sensor (6) arranged in the rim wall, which pressure sensor is electrically connected with a signal transmitter coil (8) arranged at the rim (3), as well as a signal pick-up coil (20) of a highfrequency resonant circuit signal evaluating arrangement connected with the motor vehicle in the area of the axle so as to be stationary.
Abstract: In a device for the transmission and evaluation of measurement signals for the tire pressure of tubless tires mounted rims in single and twin wheels of motor vehicles which comprises a pressure sensor (6) arranged in the rim wall, which pressure sensor (6) is electrically connected with a signal transmitter coil (8) arranged at the rim (3), as well as a signal pick-up coil (20) of a high-frequency resonant circuit signal evaluating arrangement connected with the motor vehicle in the area of the axle so as to be stationary, it is provided for the purpose of enabling signal detection also when stationary and for problem-free application to twin tires, that a first repeater coil (15), which is electrically connected with a second repeater coil (17), is arranged in the area of the signal transmitter coil (8) at the hub (12) carrying the rim (3), which hub (12) is connected with the latter so as to be fixed with respect to rotation relative to it, wherein the second repeater coil (17) is constructed as a toroidal coil whose coil axis (18) coincides with the hub axis (11), wherein the stationary signal pick-up coil (20) is arranged in the magnetic field area of the second repeater coil (17).

Patent
Dirk J. Boomgaard1
16 Feb 1989
TL;DR: In this article, the authors proposed a directional common mode trap located between the point where the communication signals are applied to the power line and the source of the electrical noise, which requires only a capacitor for each electrical phase and a 1:1 transformer having a magnetic core and single turn straight through windings.
Abstract: A power line communication system which includes an electrical power line having one or more loads which feed objectionable electrical noise back into the power line. The electrical noise is attenuated across a broad frequency range to enable effective communication over the power line by a directional common mode trap located between the point where the communication signals are applied to the power line and the source of the electrical noise. The trap requires only a capacitor for each electrical phase and a 1:1 transformer having a magnetic core and single turn, straight through windings. The trap is connected to provide a low impedance path to ground for the electrical noise, while providing a high impedance to ground for the communication signals.

Patent
29 Sep 1989
TL;DR: In this paper, a universal phase-controlled reversible power converter with one transformer with multiple windings is presented. But the power converter is not a pure sinusoid, it is a picture-of-the-line input-voltage generator.
Abstract: A universal phase-controlled reversible power converter having one transformer with multiple windings (i) couples a fixed d.c. voltage to an associated transformer winding through a fixed port having switches controlled for switching by fixed-phase signals, and (ii) couples any number of voltages having any waveform(s) whatsoever each to an associated transformer winding each through an associated variable port that has a filter with an inductor and controllable switches. Variable-phase switching control signals control the variable ports to produce any desired three-state demodulated waveform. A three-state demodulated waveform is filtered to present (i) a corresponding counter emf of any desired waveform to an input source or power, or (ii) any desired output waveform to a sink of power. Controllably producing the counter emf as a picture-of-the-line-input-voltage makes the load factor of the power converter, and all its loads, unity. Controllably producing the counter emf to either lead or lag an input power waveform gives the power converter a correspondingly controllable power factor, and permits it to serve as a power factor corrector. Controllably producing the counter emf as a pure sinusoid causes the power converter to reduce distortion on an a.c. power grid to which it is connected.

Patent
19 Apr 1989
TL;DR: In this article, a piezoresistive transducer bridge is supplied by a constant current source in one embodiment, and by a voltage of constant amplitude in another embodiment, where voltage to the bridge is reversed on a periodic basis.
Abstract: A reliable indication of temperature-compensated pressure is provided from each of the wheels of a vehicle to an operator within the vehicle. A piezoresistive transducer bridge is supplied by a constant current source in one embodiment, and by a voltage of constant amplitude in another embodiment. Voltage to the bridge is reversed on a periodic basis. The use of constant current enables compensation for temperature-induced drift in transducer bridge output. The use of constant voltage enables compensation for ambient temperature, and provides an absolute, rather than a relative indication of pressure or "flatness" within the tire. Voltage polarity reversal permits compensation of amplifier offset voltage. Energy is transmitted to an from the wheel by means of a tuned circuit which is excited by a primary coil when the vehicle's engine is running. The secondary coil mounted on the wheel may be either short-circuited or selectively opened and closed to alter the operation of the primary coil, thus providing an indication of tire pressure, that indication being detected and processed by suitable microcomputer circuitry which may exist on board the vehicle. Most of the active circuit elements of the invention may be implemented in a single monolithic integrated circuit, which can be attached to a tire valve.

Journal ArticleDOI
TL;DR: In this paper, the authors considered the design of capacitively driven, multisection, electromagnetic coil launchers, or coil guns, taking their transient behavior into account, and developed a lumped-parameter computer simulation to predict the performance of the launcher system.
Abstract: The authors consider the design of capacitively driven, multisection, electromagnetic coil launchers, or coil guns, taking their transient behavior into account. A lumped-parameter computer simulation is developed to predict the performance of the launcher system. It is shown that a traveling electromagnetic wave can be generated on the barrel by the resonance of drive coils and their capacitors. More than half of the energy initially stored in the capacitor bank can be converted into kinetic energy of the projectile in one shot, and an additional quarter can be utilized in subsequent shots, if the launcher dimensions, resonant frequency, and firing sequence are properly selected. The projectile starts smoothly from zero initial velocity and with zero initial sleeve current. Section-to-section transitions which have significant effects on the launcher performance are also discussed. Experimental results were obtained with a small model and are in good agreement with theoretical predictions. >

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the voltage induced in a pick-up coil wound around a cylindrical bulk sample of YBa 2 Cu 3 O 7−δ when driven by a weak low frequency AC magnetic field, superimposed on a weak DC magnetic field.
Abstract: We have spectrum analysed the voltage induced in a pick-up coil wound around a cylindrical bulk sample of YBa 2 Cu 3 O 7−δ when driven by a weak low frequency AC magnetic field, superimposed on a weak DC magnetic field, at 77 K. The harmonics generated by the highly nonlinear response are explained quantitatively in great detail by employing a critical state model with a field independent pinning force density, where intergranular vortices sweep in and out of the Josephson weak link regions during each AC cycle. The symmetry relation for the local flux density, which relates the first and second half of an AC cycle, is broken in the presence of a DC magnetic field, causing even harmonics to appear. This suggests high-sensitivity applications in magnetometry.

Journal ArticleDOI
TL;DR: It is shown how to create homogeneous fields at two frequencies, using an unequal distribution of capacitance and the root-mean-square deviation of field magnitude around a circle is proposed as a measure of field inhomogeneity.
Abstract: The type of radio-frequency (RF) coil known as a high-pass birdcage consists of a set of N wires arranged axially on the surface of a cylinder and connected by capacitors at each end. Such coils are widely used for NMR imaging because of the high degree of field homogeneity they provide. It is shown how to create homogeneous fields at two frequencies, using an unequal distribution of capacitance. A theoretical analysis which uses the discrete Fourier transform of the currents with respect to the angular positions of the N wires is presented. A perturbation theory analysis indicates a small sacrifice in homogeneity. The root-mean-square deviation of field magnitude around a circle is proposed as a measure of field inhomogeneity. For the case of double resonance at proton and fluorine frequencies, the loss of homogeneity is at worst 1% and is small compared to the natural inhomogeneity for an N=8 wire coil for radii up to one half the coil radius. The presence of a conducting shield degrades the homogeneity. The theoretical ideas were confirmed in a computer simulation of one particular coil design. A working coil was constructed and images obtained of proton and fluorine phantoms. >

Journal ArticleDOI
TL;DR: Results demonstrate that one‐dimensional techniques are adequate for transmural detection of metabolites provided signal origin is restricted to a column perpendicular to the left ventricle wall, and a new method of spatial localization is introduced.
Abstract: Adiabatic pulses have been employed in spectroscopic imaging and relaxation rate measurements at 4.7 T to demonstrate the feasibility of obtaining spectroscopic data from the complete sensitive volume of a surface coil using the surface coil as a transmitter and receiver. With conventional B1 sensitive pulses, spectroscopic localization or imaging techniques, such as chemical-shift imaging, yield resonance intensities that are distorted severely as a function of space, and maximal signal is detected from a small region within the complete sensitive volume of the coil. With adiabatic pulses, however, this problem is eliminated completely. In addition, a new method of spatial localization is introduced. This method, referred to as FLAX-ISIS, is a derivative of longitudinally modulated Fourier series window and ISIS approaches and utilizes adiabatic inversion and excitation pulses. The method allows construction of localized spectra for multiple regions along the surface coil axis by postacquisition data manipulation of a single set of free induction decays. These techniques were applied to the study of the myocardium using an implanted surface coil in an instrumented closed-chest canine model and in an open-chest preparation. The results demonstrate that one-dimensional techniques are adequate for transmural detection of metabolites provided signal origin is restricted to a column perpendicular to the left ventricle wall.

Patent
27 Jan 1989
TL;DR: In this article, a Zener diode is connected between the thyristor gate and the ground so as to set an instantaneous tripping pick-up of the trip device.
Abstract: In a system-powered solid-state trip device, the measurement voltage Vm, representative of the current flowing in the conductor to be protected and applied to the input of an electronic processing unit, can also be applied to the cathode of a thyristor connected in series with the trip coil and receiving on its gate, the tripping orders from the processing unit. A Zener diode is connected between the thyristor gate and the ground so as to set an instantaneous tripping pick-up of the trip device. In this way, a short-circuit in the conductor causes instantaneous tripping of the circuit breaker independently from the value of the supply voltage.


Proceedings ArticleDOI
26 Jun 1989
TL;DR: In this paper, the authors derived analytical expressions for the leakage inductance between all pairs of transformer windings, expressions which depend only on the winding geometry and the frequency of excitation.
Abstract: By considering the set of short-circuit tests which can be performed on a multiwinding transformer, analytical expressions are derived for the leakage inductances between all pairs of transformer windings, expressions which depend only on the winding geometry and the frequency of excitation. For each short-circuit test, a simplified field analysis gives the complete solution for the frequency-independent magnetic field intensity between winding layers, and the frequency-dependent distribution of magnetic field intensity within each layer. Then, for any frequency of interest, the magnetic energy stored in each winding layer and interlayer space is calculated, and the results are summed to give the total energy stored in the entire winding space of the transformer. Finally, the leakage inductance between excited and short-circuited windings is derived from the total stored energy. Experimental data are provided that illustrate the accuracy and the limitations of such leakage-inductance calculations as well as the accuracy of AC-winding-resistance calculations carried out using a similar, previously published method. >

Patent
02 Nov 1989
TL;DR: In this paper, a magnetic trip device with two plunger cores cooperating with polar parts of a fixed magnetic circuit excited by a coil is described, where the effects of the plunger core are opposing and by adjusting the inital position of the moving core assembly constituted by these two plume cores, the tripping the threshold can be adjusted with a large amplitude.
Abstract: A magnetic trip device having two plunger cores cooperating respectively with polar parts of a fixed magnetic circuit excited by a coil. The effects of the plunger cores are opposing, and by adjusting the inital position of the moving core assembly constituted by these two plunger cores, the tripping thereshold can be adjusted with a large amplitude.

Journal ArticleDOI
TL;DR: Three different stimulating coil designs were evaluated for magnetic motor cortex stimulation by comparing threshold stimulus intensities at different sites over the scalp for exciting upper and lower limb muscles, and the orientation of the inducing current over the presumed motor area was the most critical stimulation parameter.

Patent
08 May 1989
TL;DR: In this paper, an electromagnetic device including a coil and magnetic conductive member is used to control the orientation of the chassis of a motor vehicle at a preselected orientation in an active suspension system.
Abstract: An assembly (10) for use in an active suspension system for controlling the orientation of the chassis (12) of a motor vehicle at a preselected orientation. The assembly comprises an electromagnetic device including a coil and magnetic conductive member movable with respect to the coil along an axis of relative movement between the chassis and wheel (14). The coil creates a force on the magnetically conductive member in response to a current generated by a signal control as a function of acceleration and deceleration forces applied along the axis and the relative positions of the chassis and wheel along the axis of relative movement different from predetermined neutral relative positions of said chassis and wheel.

Patent
19 Jun 1989
TL;DR: In this paper, an invasive prosthesis device is disclosed which includes an electrical circuit having a cathode and an anode for mounting on opposing sides of body tissue requiring healing, the cathode is connected to a source of power for transmitting electrical stimulating signals to the anode as target.
Abstract: An invasive prosthesis device is disclosed which includes an electrical circuit having a cathode and an anode for mounting on opposing sides of body tissue requiring healing. The cathode is connected to a source of power for transmitting electrical stimulating signals to the anode as target. The invasive device includes a constant current circuit which may include either a battery source of power or a power source iductively coupled to the constant current source circuit. If the power source is inductively coupled to the constant current source a diode rectifier can be coupled between the inductive coil and constant current source for rectifying the induced ac to dc. The prosthesis device includes a porous surface area located to maximize the bonding strength between the device and the body tissue. The cathode is located in the porous area and powered to limit tissue growth to ingrowth substantially within the porous area only. The constant current circuitry including the induction coil and time constant circuit or battery as appropriate are housed within the interior of the prosthesis device together with the leads interconnecting the constant current source to the cathode.

Patent
13 Jul 1989
TL;DR: In this article, the authors present an approach for treating liquid to prevent and/or remove scale deposits, made up of at least one solenoid-type electrical coil (5) for generating a magnetic field for acting on the liquid to be treated and an electrical energizing unit (2) having at least a signal output (3, 4) for connecting the ends of the at least single coil.
Abstract: Apparatus for treating liquid to prevent and/or remove scale deposits, made up of at least one solenoid-type electrical coil (5) for generating a magnetic field for acting on the liquid to be treated and an electrical energizing unit (2) having at least one signal output (3, 4) for connecting the ends of the at least one coil (5). The energizing unit (2) is provided with means for generating an energizing signal to be varied in frequency. The at least one coil (5) can also be sited alongside a pipe (1) instead of around a pipe (1), if necessary together with the energizing unit (2) in one and the same housing. To vary the magnetic field generated as a function of the flow rate of the liquid to be treated, the energizing unit is provided with a control input (6, 7) for connecting a flow rate transducer (8).