Showing papers on "Electromagnetic coil published in 1994"

High frequency volume coils for clinical NMR imaging and spectroscopy.

Abstract: A tuned transmission line resonator has been developed in theory and in practical design for the clinical NMR volume coil application at 4.1 tesla. The distributed circuit transmission line resonator was designed for high frequency, large conductive volume applications where conventional lumped element coil designs perform less efficiently. The resonator design has made use of a resonant coaxial cavity, which could be variably tuned to the Larmor frequency of interest by tunable transmission line elements. Large head- and body-sized volumes, high efficiencies, and broad tuning ranges have been shown to be characteristic of the transmission line resonator to frequencies of 500 MHz. The B1 homogeneity of the resonator has been demonstrated to be a function of the electromagnetic properties of the load itself. By numerically solving Maxwell's equations for the fully time-dependent B1 field, coil homogeneity was predicted with finite-element models of anatomic structure, and inhomogeneities corrected for. A how-to exposition of coil design and construction has been included. Simple methods of quadrature driving and double tuning the transmission line resonator have also been presented. Human head images obtained with a tuned transmission line resonator at 175 MHz have clearly demonstrated uncompromised high field advantages of signal-to-noise and spatial resolution.

Detection and location of interturn short circuits in the stator windings of operating motors

Abstract: One major cause of motor failures is breakdown of the turn insulation leading to puncture of the groundwall. Early detection of interturn shorts during motor operation would eliminate consequential damage to adjacent coils and the stator core reducing repair costs and motor outage time. In addition to the benefits gained from early detection of turn insulation breakdown, significant advantages would accrue by locating the faulted coil within the stator winding. Fault location would not only increase the speed of the repair, but would also permit more optimal scheduling of the repair outage. This work was successful in practically implementing a theory to predict changes in the axial leakage flux resulting from stator winding interturn shorts and in developing an algorithm to locate the position of the faulted coil. An experimental setup consisting of a 200 hp motor loaded by a generator was used to validate this theory. Suitable transducers were developed and installed on this motor. Measurement using this experimental configuration clearly validated the theoretical model. On the basis of this experimental work an instrument to continuously monitor for shorted turns is under development. >

Induction charging apparatus

Abstract: The induction charging apparatus has a power source unit and a device unit which can be detachably coupled to the power source unit. The power source unit has a first casing having one end opened, a primary coil provided in the first casing, an oscillator for supplying an alternating current to the primary coil to generate magnetic fluxes, and a depressible member movably provided and closing the open end of the first casing. The depressible member is movable between a lift position at which the magnetic fluxes are substantially located under the depressible member, and a depressed position at which portions of the magnetic fluxes are substantially located over the depressible member. The device unit has a second casing having one end detachable to the open end of the first casing, a secondary coil provided in the second casing and adjacent to the one end, and rechargeable battery provided in said second casing for receiving power from the secondary coil. When the second casing is attached to the first casing, the depressible member is moved to the depressed position to electromagnetically couple the primary and secondary coils.

10 kHz inductively coupled power transfer-concept and control

Abstract: Electric vehicles are used throughout the materials handling industry because they are low cost, reliable, inoffensive, and simple to control compared to alternative forms of motive power. But conventional methods of power transfer to the vehicle such as electrified tracks and batteries have remained less than ideal; that is until the recent development of a novel inductively coupled power transmission (IPT) system that is clean and spark-free, is robust to dust and water, and has very low maintenance. Load power in an IPT system is sourced at 10 kHz from tuned pick-up coils mounted adjacent to, but not touching, a sealed track conductor driven by a resonant power electronic converter. Power transfer of several kilowatts is possible from a single pick-up coil, and multiple pick-ups can be powered from the same track. The paper describes the IPT concept and presents practical control solutions to some important problems.

Complete transformer model for electromagnetic transients

Abstract: A complete, three phase transformer model for the calculation of electromagnetic transients is presented. The model consists of a set of state equations solved with the trapezoidal rule of integration in order to obtain an equivalent Norton circuit at the transformer terminals. Thus the transformer model can be easily interfaced with an electromagnetic transients program. Its main features are: (a) the basic elements for the winding model are the turns; (b) the complete model includes the losses due to eddy currents in the windings and in the iron core; and (c) the solution of the state equations is obtained in decoupled iterations. For validation, the frequency response of the model is compared with tests on several transformers. Applications to the calculation of transients are given for illustration. >

Inductively coupled RF tracking system for use in invasive imaging of a living body

Abstract: RF tracking system employs a RF invasive device coupled to surgical tracking equipment for tracking the invasive device. An inductive coupling permits the device to be quickly coupled to, and decoupled from, the equipment. The coupling comprises an inducting coil which transmits a signal from the surgical tracking equipment to a communicating coil in the invasive device. The signal received by the communicating coil passes along leads to a tracked coil in a distal end of the invasive device. The tracked coil transmits the signal as RF energy which is received by the surgical tracking equipment which superimposes the position of the distal end of the invasive device on an X-ray image and displays it on a monitor A sterile shield is employed as a sterile barrier between the inducting coil and the equipment end of the invasive device to prevent contamination of the invasive device by the inducting coil. The cross-section of the invasive device at its equipment end can be made identical to the rest of the invasive device to permit other invasive devices to pass completely over the invasive device.

Inductive power pick-up coils

Abstract: A loosely coupled inductive power transfer system suitable for transferring power to a mobile conveyer platform or a vehicle has pick-up coils wound on flux concentrator(s). One or more large flat horizontal ferrite cores (607, 608) are used to concentrate the horizontal component of magnetic flux from an extended volume into one or more secondary or pick-up coils (613). Each shock-resistant core comprises an array of many individual strips of ferrite held in close contact. One, more usually two, or perhaps more resonant pick-up windings are wound about each core and each winding has a shorting switch (within 602, 603, ...) placed across it. A controller (601) connects a controlled output voltage on to an output bus (605, 606) from the best-placed pick-up winding on any one core at any moment, while holding the others in a shorted hence inactive state.

Steerable open-lumen catheter

Abstract: A steerable catheter (10) comprises an elongated catheter body (12), a tip portion (14), first and second lumens (18, 20), a tightly wound coil (48), a puller wire (36), and a control handle.

Coil polymer composite

Abstract: A coil polymer composite tubular body is disclosed, such as for use in medical applications. The body comprises a spring coil having at least one central lumen extending axially therethrough, for receiving medical implements, fiber optics, suction or transmission of fluids such as for irrigation or drug delivery. An elastomeric layer on the spring coil provides a substantially water impermeable seal. In one particular embodiment, the composite tubular body is provided with a laterally deflectable distal tip.

Steerable flexible microsurgical instrument with rotatable clevis

Abstract: A steerable flexible microsurgical instrument is provided with a rotatable clevis. The instrument includes a flexible coil, a flexible pull wire extending through the coil, a clevis which is rotatably coupled to the distal end of the coil, a handle coupled to the proximal end of the coil, and end effectors coupled to the clevis and the pull wire. The clevis is coupled to the distal end of the flexible coil by a bushing which allows axial rotation of the clevis relative to the coil. The pull wire is formed from torsionally obdurate material and is coupled at its distal end to the end effector and at its proximal end to a movable part of the handle. The handle is provided with mechanism for rotating the pull wire relative to the coil and a mechanism for translating the pull wire relative to the coil. Translation of the pull wire relative to the coil moves the end effector relative to the clevis and rotation of the pull wire relative to the coil rotates the clevis and end effector relative to the coil.

Self testing circuit breaker ground fault and sputtering arc trip unit

Abstract: Ground fault trip units for circuit breakers are tested by a passive test circuit which includes a test conductor passing through the current transformer sensing coil(s), and a test switch which selectively connects the test conductor in a loop which simulates a neutral-to-ground fault. In a dormant oscillator ground fault test circuit, the test conductor loop passes through both sensing coils. When the neutral-to-ground detector is combined with a sputtering arc fault detector sharing a common sensing coil, testing of all the components is accomplished by adding an additional test circuit which injects pulses derived from the line conductor into the sensing coil secondary, or which alternatively, connects a capacitor charged from a DC supply across the sensing coil secondary. Either of these alternative test circuits generates the successive events needed to produce a sputtering arc trip.

Bending actuator having a coil sheath with a fixed distal end and a free proximal end

Abstract: A bending drive member to bend a bending member is arranged to extend in the direction of length of an elongate tube having flexibility, and attached to near the distal end of the tube with the distal end of the bending drive member being restricted in its position. The bending member drive member comprises a shape memory member formed by bundling together a plurality of wire-like shape memory materials each having a length, that spans from the position of one end to the other end, reversibly changed upon heating/cooling. The length of the shape memory member is changed dependent on a drive signal from a unit with a capability of heating. A non-compressive coil sheath through which the bending drive member extends is fixed at a distal end thereof to the elongate tube while the proximal end of the coil sheath is a free end with respect to the elongate tube.

Control method for magnetic stereotaxis system

Abstract: A control method permits the operation of multiple superconducting magnetic coils so as to move a magnetic object to precisely specified locations within the body under command of a physician-operator observing the motion with live fluoroscopic imaging fused with more detailed preoperative imaging of some other kind A computer contains the preoperative images and the fluoroscopic images, as well as the means to effect changes in the coil currents so as to accomplish the desired magnetic object motion and positioning The control method operates the coils in pairs on opposite sides of the body in a manner to minimize the necessary current changes, thus avoiding the quenching of the superconducting coils Combinations of these pairs can execute motion of the magnetic object in any direction in an impulsive manner and with high precision The method should function well and provide advantages with coils which are not superconducting as well The method overcomes the redundance present in the limited constraints given by a simple movement vector by the physician-operator

Shorted magnetoresistive head leads for electrical overstress and electrostatic discharge protection during manufacture of a magnetic storage system

Abstract: The magnetoresistive (MR) sensor in a magnetic read/write transducer is protected against the effects of electrical overstress and electrostatic discharge during the manufacture and assembly of a magnetic storage system. The conductive leads of a magnetoresistive (MR) sensor element are shorted together to provide a low resistance, conductive path bypassing the MR element and minimizing electrical current through the MR sensing element during discharge of static electrical charge. The MR sensor lead terminal pads provided on the transducer/slider surface are shorted together by soldering. The other transducer elements such as the MR magnetic shields, the inductive coil and the inductive magnetic yoke structure can also be shorted to the MR sensor leads by soldering together the lead terminal pads at the slider surface. Alternatively, a twisted conductor pair may be used to short the MR terminals together. Remotely located protective devices, such as reversed diode pairs, can also be connected across the MR sensor element utilizing the twisted pair. The short is removed prior to placing the MR head into operation in the magnetic storage system.

Implantable electromagnetic hearing transducer

Abstract: An electromagnetic transducer for improving hearing in a hearing impaired person comprises a magnet assembly and a coil secured inside a housing which is fixed to an ossicle of a middle ear. The coil is more rigidly secured to the housing than the magnet. The magnet assembly and coil are configured such that conducting alternating electrical current through the coil creates magnetic field thereby causing the magnet assembly and coil to vibrate relative to one another. Because the coil is more rigidly secured to the housing than the magnet assembly, the vibrations of the coil cause the housing to vibrate. The vibrations are conducted to the oval window of the ear via the ossicles. In alternate embodiments, the transducer is secured to ossicular prostheses that are secured within the middle ear.

Apparatus and method for use in medical imaging

Abstract: An apparatus and method for use in medical imaging simulate within an imaging coil normal movements of body parts such as joints, and improve imaging of soft tissue and bony parts as compared to a static system in which images are taken of a joint in only one position. A joint or body parts is moved into various positions in multiple planes within its range of motion while a series of images are taken of the joint in the different positions. The images are collated into a cine format to effectively show the joint in motion. A surface or volume coil may be coupled for movement with the joint or body part and maintained in the proper spatial relationship with the primary coil's electromagnetic field. The systems may be provided as mechanisms usable with existing imaging tables to reduce cost, or may be built into a new imaging table. It is possible to use a larger primary coil, allowing increased range of movement. Traction may be applied to a joint being imaged, in order to load the joint.

Silicon micromachined two-dimensional galvano optical scanner

Abstract: A new two-dimensional galvano optical scanner realized by silicon micromachining is proposed. To realize two-dimensional operation a silicon micromachined gimbal structure was introduced. It is possible to sense rotational angle using electromagnetic coupling between driving coil and fixed detecting coil. >

Implantable magnetic hearing aid transducer

Abstract: A magnetic transducer (100) for improving hearing in a hearing impaired person comprises a magnet assembly (12) and a coil (14) secured inside a housing (10) which is fixed to an ossicle of a middle ear (JJ). The coil (14) is more rigidly secured to the housing (10) than the magnet (12). The magnet assembly (12) and coil (14) are configured such that conducting alternating electrical current through the coil (14) causes magnetic fields of the coil (14) and magnet assembly (12) to cause the magnet assembly (12) and coil (14) to vibrate relative to one another. Because the coil (14) is more rigidly secured to the housing (10) than the magnet assembly (12), the vibrations of the coil (14) cause the housing (10) to vibrate. The vibrations are conducted to the oval window of the ear via the ossicles. In alternate embodiments, the transducer (100) is secured to ossicular prostheses that are secured within the middle ear (JJ).

Electrical characteristics and electron heating mechanism of an inductively coupled argon discharge

Abstract: The external electrical characteristics of inductively coupled argon RF discharges at 13.56 MHz have been measured over a wide range of power at gas pressures ranging from 3 mTorr to 3 Torr. External parameters, such as coil voltage, current and phase shift, were measured. From these measurements the equivalent discharge resistance and reactance, the power transfer efficiency and the coupling coefficient between the primary coil and the plasma were determined as a function of discharge power and gas pressure. The efficient RF power transfer and the large value of the effective electron collision frequency found here at low gas pressure suggest some collisionless electron heating mechanisms. This mechanism is identified as non-local electron heating in the inhomogeneous RF field due to spatial dispersion of the plasma conductivity.

Investigation of electron source and ion flux uniformity in high plasma density inductively coupled etching tools using two‐dimensional modeling

Abstract: Inductively coupled plasma (ICP) sources are being developed as reactors for high plasma density (1011–1012 cm−3), low‐pressure (<10–20 mTorr) etching of semiconductors and metals for microelectronics fabrication. Transformer coupled plasmas (TCPs) are one variant of ICP etching tools which use a flat spiral coil having a rectangular cross section powered at radio frequencies (rf) to produce a dense plasma in a cylindrical plasma chamber. Capacitive rf biasing of the substrate may also be used to independently control ion energies incident on the wafer. The uniformity of generating the plasma and the uniformity of the flux of reactants to the substrate are functions of the geometry and placement of the coil; and of the materials used in the construction of the chamber. In this article, we use results from a two‐dimensional model to investigate design issues in TCPs for etching. We parametrize the number of turns and locations of the coil; and material properties of the reactor. We find that at low pressure, designs which produce ionization predominantly at larger radii near the edge of the wafer produce more uniform ion fluxes to the substrate. This results from a ‘‘converging’’ ion flux which compensates for losses to lateral surfaces. Careful attention must be paid to metal structures in the vicinity of the coils which restrict the azimuthal electrical field. This situation results in reduced power deposition at large radii, which can be compensated by over sizing the coil or by using auxiliary solenoidal coils. The plasma and neutral transport, dominated by diffusion, treats the advective flow from the gas inlets and pump port as local sources and sinks which are rapidly volume averaged.

Fibered vasooclusion coils

Abstract: This invention is a vasoocclusive device. It is placed in the vasculature of an animal to form thrombus in a selected site such as an aneurysm or AVM. The device uses a central coil having thrombogenic fibers placed on the coil in a specified fashion. The coil will pass through the lumen of a vascular catheter and form a convolution when ejected from the catheter's distal end. The fibers are attached to the coil and cooperate with the coil so that upon ejection from the catheter, the convoluted coil forms a shape in which the central region contains the majority of these fibers.

A magnetic thin film inductor and its application to a MHz switching dc-dc converter

Abstract: The authors propose a novel structured magnetic thin film inductor using rotation magnetization only. The thin film inductor has a sandwich structure, which consists of a double-rectangular spiral coil between top and bottom CoZrNb amorphous thin films. The sputtered CoZrNb amorphous magnetic thin films have uniaxial magnetic anisotropy induced by direct current field annealing. The easy magnetization axis is directed to the main axis of the rectangular spiral coil. Hence, only the rotation magnetization process dominates in this device. The typical specifications are as follows; 3.5/spl times/5.5 mm in size, inductance of 1 /spl mu/H constant up to 10 MHz, and a quality factor of 10 at 10 MHz. A MHz switching chopper dc-dc converter has been developed by using this thin film inductor, bare-chip semiconductor devices (a power MOSFET and a Schottky barrier diode), and a multilayer ceramic capacitor. This converter with a 0.1 cc volume has an output power over 1 W at 5 MHz switching, and the power density exceeds 10 W/cc (160 W/in/sup 3/). >

Identification system antenna with impedance transformer

Abstract: The present invention discloses an electromagnetic device which includes a magnetic flux producing apparatus for producing a magnetic flux path loop. The magnetic flux producing apparatus preferably comprises a magnetic core 20 surrounded by electrical windings 22. A strip of electrically conductive material 24 is disposed such that it passes through the magnetic flux path loop and overlies the windings 22. The strip 24 has a width which is substantially greater than its thickness. The device may further include an antenna 16 which is electrically coupled to the strip 24.

A new toroidal-meander type integrated inductor with a multilevel meander magnetic core

Abstract: A novel toroidal-meander type integrated (TMTI) inductor with a multilevel meander magnetic core has been designed, fabricated, and integrated onto a silicon wafer. In a conventional inductor, conductor wires are wound around magnetic cores. By switching the roles of conductor wire and magnetic core, i.e., by 'wrapping' a magnetic core around a conductor wire, the same effect can be realized in a planar geometry. This geometry has been implemented using multilevel metal interconnection schemes, by interlacing a meander planar conductor with a multilevel meander magnetic core. The total inductor size is 4 mm/spl times/1.0 mm, the coil has 30 turns, and the magnetic material used was electroplated nickel(81%)-iron(19%) Permalloy. An inductance of 30 nH/mm/sup 2/ was achieved at a frequency of 5 MHz. The fabrication sequence of this inductor structure is entirely compatible with post-processing of standard bipolar and CMOS circuitry, as well as the fabrication of multichip module substrates, thus enabling the integration of the inductor structure with control circuitry for applications such as filters, sensors, magnetic microactuators, and low-power voltage converters. >

Trailer alignment device with visual display

Abstract: A visual aid for assisting a driver backing up a towing vehicle to a drawn vehicle. A visual display includes a flat screen upon which are depicted images in the form of silhouettes or like simulations of the respective vehicles. This effect is provided by partially and selectively illuminating the screen. A sensor is placed on at least one of the vehicles for detecting relative alignment therebetween and proximity thereof. The sensor generates a signal which controls the screen. The silhouettes are moved on the screen in proportion to the actual relationship of the two vehicles. In a preferred embodiment, the image of the towing vehicle is stationary, and the image of the drawn vehicle moves responsive to input from the sensor. The sensor may employ an emitting coil and an induction coil, or may be of the reflected energy type, such as radar and infrared radiation. The display control preferably comprises a microprocessor. The visual aid has an on-off switch, a proximity readout, and an alarm annunciating the presence of an object interposed between the tow vehicle and the draft vehicle.

Electric rotating machine

Abstract: The provision of an electric rotating machine which can reduce the mechanical and thermal loads applied thereto. Coil arms and coil trunks are provided in roughly parallel orientation to the end faces of an armature core only through insulating rings and insulating spacers. Metal brush is disposed on coil arms, whereby the overall length of the armature can be remarkably shortened. In addition, a commutator, conventionally necessary, can be eliminated, whereby the length of the production process for the armature can be reduced. Moreover, in an arrangement where projections of the upper coil arm are fit in holes of the insulating spacer, as the displacement of the upper coil arm towards the outer periphery is regulated, the length of the axial protrusions of the upper coil arm from the end face of the armature core can be minimized. In addition, as extension portions and of the coil trunks are strongly pressed against and fixed to the side of armature core by fixing members, the resistance to the centrifugal force can be remarkably improved. Furthermore, as the extension portion of the lower coil arm is fit in a recessed part of the insulating spacer, the displacement of the lower coil arm in the axial direction towards the outer periphery can be prevented. Accordingly, the electric rotating machine according to the present invention can withstand more than two times as high a rotational speed as that of the conventional structure.

Apparatus and method for high speed data communication between an external medical device and an implantable medical device

Abstract: A method of communicating data between an external device and an implantable medical device wherein a first pulse is transmitted as electromagnetic energy from one device to the other, is received and stored as electrostatic energy in the second device and, after a delay period representing data to be communicated, the stored energy is released and transmitted as electromagnetic energy back to the first device. A communications circuit in the implantable device for accomplishing the method includes an antenna coil, a non-linear electronic component in circuit communication with the antenna coil, a storage capacitor in circuit communication with the antenna coil and non-linear electronic component for storing energy received by the antenna coil, and a switch for selectively connecting the charged storage capacitor and the antenna coil to discharge the charge stored in the capacitor into the antenna coil.

Apparatus for dispensing heated fluid materials

Abstract: An electromagnetic dispenser for dispensing viscous heated fluids, such as hot melt adhesives. A fixed pole extends from a fluid chamber. The coil is located about a portion of the fixed pole and spaced from the fluid chamber to isolate the coil from the fluid flow path of the adhesive. The coil is insulated from the heat which is conducted from the adhesive as well as provided with a heat sink for dissipating heat. A plunger is mounted within the fluid chamber for reciprocal movement therein to open and close dispensing orifice in response to the field generated by the coil. When mounted to a service block, the coil assembly may be serviced without disconnecting the dispenser body from the source of heated fluid.

A full procedure to model high frequency transformer windings

Abstract: A full procedure to model high frequency magnetic components has been developed. A finite element analysis (FEA) tool is used to compute the frequency behavior of the windings, taking into account geometry and frequency effects, like skin, proximity, interleaving, gap and end effects. The capacitive effects among the windings of the components are also taken into account. From these data, a model for the windings is developed by means of discrete components and differential equations that present the same frequency behavior as the actual component. Although the model has been developed for behavioral simulators, it can also be used in electrical simulators. >