Showing papers on "Magnetic core published in 1997"

Submerged reciprocating electric generator

Abstract: A submerged reciprocating electric generator is placed below the ocean surface and creates electric power from the surface ocean swells. The generator coil reciprocates linearly in response to an external force acting on a float by passing ocean swells. A cable connects the float on the ocean surface with the reciprocating coil of the submerged generator. A magnetic field is focussed through the coil as it reciprocates, creating an electromotive force in the coil. The magnetic field is created in such a manner as to provide uniform field of a single magnetic orientation throughout the entire length of motion of the reciprocating coil. The generator includes a base formed on the ocean floor supporting magnetic core having a generator coil movably mounted therein and connected to a float with a cable passing through cable alignment bearings. Electromagnetic windings are mounted at the closed end of the generator magnetic flux core.

Performance of a high-Tc superconducting fault current limiter-design of a 6.6 kV magnetic shielding type superconducting fault current limiter

Abstract: Superconducting fault current limiters for electric power systems have been researched. A magnetic shielding type superconducting fault current limiter is developed in the authors' research on superconducting fault current limiters. This limiter consists of a copper primary winding, a superconducting cylinder, an iron core and a control coil. The superconducting cylinder has a Bi2212 thick film on a MgO substrate. The control coil consists of some metallic rings, and the fault level can be adjusted by changing the number of the rings. To design a prototype limiter, the AC magnetic shielding and loss characteristics of small models were measured. The prototype limiter is 6600 V in rated voltage and 400 A in rated current. The superconducting cylinder is 0.45 m in diameter and about 1 m in height. Only the superconducting cylinder was designed to be cooled by liquid nitrogen. The experimentally manufactured limiter is about 1.3 m in width, about 0.6 m in depth and about 2 m in height.

Magnetic film inductors for radio frequency applications

Abstract: Responding to the increasing demand for miniaturization and circuit integration of rf inductors we analyze various aspects of designing planar inductive circuits based on magnetic films as well as demonstrate substantially enhanced inductance characteristics for some prototype structures.

Iron loss analysis of Mn-Zn ferrite cores

Abstract: Iron loss measurements of Mn-Zn ferrite cores up to the megahertz range are reported. Taking the dc magnetic hysteresis, the eddy, and displacement currents into account, magnetic and electric field distributions in the cores are computed with the cylindrical coordinates and Bessel functions. The computed iron loss due to the magnetic and electric fields is compared with the experimental value at different exciting frequencies. It is noted that the computed iron loss becomes considerably smaller than the experimental at high frequencies. In order to explain the difference between the computed and experimental iron losses, a new magnetic field component yielding a dynamic magnetic loss is assumed and added to the magnetic field intensity of the dc magnetic hysteresis. This assumption is verified by evaluating the iron losses in different size cores composed of the same ferrite material. Displacement current distribution in a ferrite core depends on the cross-sectional area of the magnetic flux path, which brings about the dependence of the frequency characteristics of the iron loss upon core size.

Electrical application of high T/sub c/ superconducting saturable magnetic core fault current limiter

Abstract: A saturable magnetic core electrical fault current limiter (FCT) designed with a high T/sub c/ superconducting (HTS) DC bias winding is described. The HTS winding is prepared by using a Ag-clad (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub O10+x/ HTS wire. The limiting behaviour of this FCL is investigated, and its electrical application is considered in an electrical power transmission system. The results show that this FCL limits fault currents effectively and is a possible solution for reducing power system fault currents.

Thin-film magnetic head having a portion of the upper magnetic core coplanar with a portion of the lower magnetic core

Abstract: A thin-film magnetic head comprising a lower magnetic core formed on a substrate, an upper magnetic core formed on the lower magnetic core with a magnetic gap therebetween, and a coil interposed between the lower magnetic core and the upper magnetic core as insulated from the lower magnetic core and the upper magnetic core, characterized in that at least either of the lower magnetic core and the upper magnetic core comprises a front body of a magnetic pole facing a magnetic recording medium and a rear body of a magnetic pole having part thereof superposed on the front body of the magnetic pole, the rear body of the magnetic pole is disposed as recessed from the head surface facing the medium and held in contact with the front body of the magnetic pole in a plane, the plane is terminated at a rear of the end of the front body of the magnetic pole, and the rear body of the magnetic pole has a shape curved or bent in the direction opposite to the magnetic gap, and further the front body of the magnetic pole is composed of a magnetic member embedded in a trench formed in advance in an insulating layer.

Magnetic deflectors and charged-particle-beam lithography systems incorporating same

Abstract: Magnetic deflectors for charged particle beams are provided. The magnetic deflectors comprise at least one pair of coils to provide high deflection sensitivity over large regions of uniform deflection without increasing the size of the magnetic core used by the deflectors. Charged-particle-beam lithography systems using such deflectors are also disclosed.

Thin film heads having solenoid coils

Abstract: A low-noise toroidal thin film head ("TFH") device has low coil resistance and inductance, especially suitable for very high magnetic recording areal densities and channel frequencies. The length of a toroidal coil turn is only about 20-30% that of the length of an average turn in the conventional planar spiral coil design. This allows either reduction of the device thermal noise (by about 6 dB) and/or increase of the device operational frequency bandwidth (by a factor of 3-5). The toroidal coil coupling efficiency between each turn and the magnetic core is practically 100%, thereby improving the write and read-back efficiencies. In one embodiment a non-via large back-closure contact area is provided between the bottom and top magnetic poles along their entire back-side width, and all other open branches and loose ends in the magnetic circuit are eliminated. The magnetic core has a gradual, smooth toroidal (or a horse-shoe) shape with no loose ends, nooks, crevices, or sharp corners. The larger back-closure contact area decreases the magnetic core reluctance and improves the device efficiency. Utilization of a soft non-magnetic seed-layer, such as gold, eliminates interference noise due to the conventional magnetic (NiFe) seed-layer. Slight mechanical texturing (scratching) of the seed-layer along the intended easy axis helps to define and induce strong magnetic uniaxial anisotropy in the plated magnetic poles. All these features facilitate significant reduction of Barkhausen and other sources of device noise. Embodiments include conventional TFH's, Planar TFH's, Pinched-Gap TFH's, and various versions of Magnetoresistive (MR) TFH's.

Process for producing microcoils and microtransformers

Abstract: A process for producing single-layer or multi-layer microcoils or microcoil arrays that optionally have a magnetic core area to increase the coil inductance and to guide the magnetic flux. In this process, plastic films (e.g., made of polyimide or polyester), are applied using pressure and heat to serve as the insulation layers. This eliminates the need for curing the insulation and expensive leveling operations.

Equivalent circuit of mush wound AC windings for high frequency analysis

Abstract: The paper describes a lumped parameter equivalent circuit for the HF analysis of mush wound coils of AC windings. The equivalent circuit takes account of turn-to-turn and turn-to-iron stray capacitances. Dissipative phenomena due to eddy currents in the coil wires and the laminated iron core are also considered. The parameter identification is based on sinusoidal impedance measurements on a test coil. The model of a multi-coil AC stator winding can be easily derived from the proposed equivalent circuit. This model allows one to predict both common- and differential-mode conducted EMI in switching converters supplying AC motors. The simulation results obtained by PSpice are in good agreement with the experimental data.

Magnetic core-coil assembly for spark ignition systems

Abstract: A magnetic core-coil assembly generates an ignition event in a spark ignition internal combustion system having at least one combustion chamber. The assembly comprises a magnetic core of amorphous metal having a primary coil for low voltage excitation and a secondary coil for a high voltage output to be fed to a spark plug. A high voltage is generated in the secondary coil within a short period of time following excitation thereof. The assembly senses spark ignition conditions in the combustion chamber to control the ignition event. The assembly is constructed from sub-assembly parts that can be manufactured with existing machines at reasonable cost.

Passive fault current limiting device

Abstract: A passive current limiting device and isolator is particularly adapted for use at high power levels for limiting excessive currents in a circuit in a fault condition such as an electrical short. The current limiting device comprises a magnetic core wound with two magnetically opposed, parallel connected coils of copper, a high temperature superconductor or other electrically conducting material, and a fault element connected in series with one of the coils. Under normal operating conditions, the magnetic flux density produced by the two coils cancel each other. Under a fault condition, the fault element is triggered to cause an imbalance in the magnetic flux density between the two coils which results in an increase in the impedance in the coils. While the fault element may be a separate current limiter, switch, fuse, bimetal strip or the like, it preferably is a superconductor current limiter conducting one-half of the current load compared to the same limiter wired to carry the total current of the circuit. The major voltage during a fault condition is in the coils wound on the common core in a preferred embodiment.

Stator core of motor and its manufacture

Abstract: PROBLEM TO BE SOLVED: To enhance the efficiency by reducing iron loss and copper loss by arranging laminated yokes and laminated teeth, in such a manner that the direction for easy magnetization of a grain oriented flat rolled magnetic steel sheets almost aligns with the direction of a magnetic flux flowing through a laminated iron core during motor operation. SOLUTION: Laminated yokes 110 and laminated teeth 120 are constituted by laminating sheets formed to a circular ring shape from a band-shaped raw material punched such that respective grain oriented flat rolled magnetic steel sheets are punched so as to align the direction L for easy magnetization with the direction of a magnetic pass in the iron core of a stator core 100. The laminated yokes 110 forming the outer core and laminated teeth 120 forming the inner core are jointed and fixed with an opening 113 and a base end portion 121a, thereby forming the stator core 100 of the motor. By doing this, the iron loss can be reduced and the same output can be made possible with a low input, and copper loss can be also decreased, resulting in considerable improvement in the efficiency.

Thermal modeling of pot core magnetic components used in high frequency static converters

Abstract: This paper presents the essential aspects related to the thermal modeling of the magnetic components (power transformers and inductors) used in high frequency static converters. The main difficulties in the modeling of heat transfer mechanisms in such components are discussed and a thermal model for pot core magnetic components, represented by an equivalent circuit, is described.

Quasi-integrated magnetic an avenue for higher power density and efficiency in power converters

Abstract: This paper presents several topologies that lead to a better utilization of a transformer's magnetic core. In these topologies, the main transformer also becomes a magnetic storage element, reducing the size of the output filter. Quasi-integrated magnetics are presented as an intermediate step between conventional and fully-integrated magnetics underlying their advantages and limitations. The authors also present quasi-integrated magnetic topologies with and without secondary winding taps. Two methods of eliminating the secondary winding taps are suggested, one by using a current-doubler and the second by employing two symmetrical transformers. Two 100 W, 5 V, 20 A experimental power converters were built and evaluated, using quasi-integrated magnetics under two different implementations.

Thin film magnetic head, magnetoresistance effect magnetic head and composite magnetic head

Abstract: A thin-film magnetic head, a magnetoresistance effect magnetic head and an MR inductive head are disclosed. The thin-film magnetic head has one of thin-film magnetic cores stacked on a substrate and formed of two magnetic films and a non-magnetic film held between them, with a current flowing through the thin-film magnetic core in the direction of hard axis thereof. The magnetoresistance effect magnetic head has one of a pair of shield cores having a magnetoresistive element between them formed of two magnetic films and a non-magnetic film held between them, the magnetoresistive element being electrically connected to the shield core, with a sense current flowing through the shield core. The current flowing through the one shield core via the magnetoresistive element is preferably an AC of decrement amplitude for demagnetizing the shield core along with a DC sense current. Also, this current preferably flows in the direction of hard axis of the shield core so that magnetic properties of the shield core are stabilized or demagnetized by the magnetic field generated in the direction of easy axis. The MR inductive head has a second thin-film magnetic core as a common magnetic body of an MR head and an inductive head on one substrate, formed of two magnetic films and a non-magnetic film held between them, with a current flowing through the second thin-film magnetic core in the direction of hard axis thereof.

Low-noise toroidal thin film head with solenoidal coil

Abstract: The invention relates to a low-noise toroidal TFH device including a solenoidal or helical coil with low coil resistance and inductance, especially suitable for very high magnetic recording areal densities and channel frequencies. The length of a solenoidal coil turn is only about 20-30% that of an average turn in the conventional planar spiral coil design. This allows either reduction of the device thermal noise (by about 6 dB) and/or increase of the device operational frequency bandwidth (by a factor of 3-5). Also, the solenoidal coil coupling efficiency between each turn and the magnetic core is practically 100%, thereby improving the write and read-back efficiencies. Other features of the invention include a non-via large back-closure contact area between the bottom and top magnetic poles along their entire back-side width, and elimination of all other open branches and loose ends in the magnetic circuit. The magnetic core has a gradual, smooth toroidal (or a horse-shoe) shape with no loose ends, nooks, crevices, or sharp corners. The larger back-closure contact area decreases the magnetic core reluctance and improves the device efficiency. Utilization of a soft non-magnetic seed-layer, such as gold, eliminates interference noise due to the conventional magnetic (NiFe) seed-layer. Slight mechanical texturing (scratching) of the seed-layer along the intended easy axis helps to define and induce strong magnetic uniaxial anisotropy in the plated magnetic poles. All these features facilitate significant reduction of Barkhausen and other sources of device noise.

Magnetic core assemblies

Abstract: An electromagnetic device comprising a winding arrangement 1, 2,3 and a magnetic core arrangement 7, 8, 9 with a permeability greater than one in which the windings 1, 2, 3 and the magnetic cores 7, 8, 9 are arranged such that the B-field induced in the magnetic cores follows a similar pattern as the H-field generated by current flowing in the windings. The magnetic cores 7, 8, 9 may be formed from magnetically oriented amorphous material formed into insulated wires or cables. The said wires or cables may have a rectangular or circular cross section. The said magnetic wires or cables may be at least partially encapsulated by a material including soft magnetic material. Alternatively the core may be formed of laminated material forming yoke and limb members with soft magnetic powder material being compacted into one or more of the angular regions of the core joints to provide the core with curved contours. The windings may be formed using a cable with conducting means insulated by an extruded plastic layer with inner and outer semiconductive layers separated by an insulating intermediate layer. The semiconductive layers may be arranged to form equipotential surfaces which confine the electric field of the cable.

Inductance and quality-factor evaluation of planar lumped inductors in a multilayer configuration

Abstract: Integral representations for the self and mutual inductance of planar loops on a multilayered structure are derived. The integrals are of the Sommerfeld type and can be easily evaluated under the quasi-static approximation which is validated by the small dimensions relative to a wavelength. Enhancement of loop inductance by inclusion of a magnetic layer is investigated. It is shown that such a layer can increase the inductance by a percentage which has the upper limit of [(/spl mu//sub r/-1)/(/spl mu//sub r/+1)]/spl times/100%, where /spl mu//sub r/ is the relative permeability of the layer. A study is also made on the inductor quality factor (Q) as affected by losses caused by finite electrical conductivity of the magnetic layer and the underlying substrate.

Single coil bistable, bidirectional micromechanical actuator

Abstract: Micromechanical actuators capable of bidirectional and bistable operation can be formed on substrates using lithographic processing techniques. Bistable operation of the microactuator is obtained using a single coil and a magnetic core with a gap. A plunger having two magnetic heads is supported for back and forth linear movement with respect to the gap in the magnetic core, and is spring biased to a neutral position in which the two heads are on each side of the gap in the core. The single electrical coil is coupled to the core and is provided with electrical current to attract one of the heads toward the core by reluctance action to drive the plunger to a limit of travel in one direction. The current is then cut off and the plunger returns by spring action toward the gap, whereafter the current is reapplied to the coil to attract the other head of the plunger by reluctance action to drive the plunger to its other limit of travel. This process can be repeated at a time when switching of the actuator is required.

Encapsulated package for power magnetic devices and method of manufacturing therefor

Abstract: An encapsulated package for a power magnetic device and a method of manufacture therefor. The power magnetic device has a magnetic core subject to magnetostriction when placed under stress. The package includes: (1) compliant material disposed about at least a portion of the magnetic core and (2) an encapsulant substantially surrounding the compliant material and the magnetic core, the compliant material providing a medium for absorbing stress between the encapsulant and the magnetic core, the compliant material reducing the magnetostriction upon the magnetic core caused by the stress from the encapsulant. In one embodiment, the encapsulant includes a vent to an environment surrounding the package. The vent provides pressure relief for the compliant material, allowing the compliant material to substantially eliminate the magnetostrictive effects.

Low-loss magnet core for high frequency claw-pole-type alternator

Abstract: A low-loss magnetic core of the claw-pole type for use in generating electrical power with a high frequency alternator is disclosed. A rotor, driven by a shaft, is made of pairs of individual poles of alternating polarity nested radially around a shaft. The rotor poles overlap each other axially and interleave circumferentially. The rotor poles are excited by a common field coil. The pairs of individual poles are made from laminated electrical steel or magnetic steel, with laminate shapes bent and bundled together to form an open three dimensional shape vaguely similar to one and one quarter turns of a spiral shape. A stator is made of ring bundles of laminated electrical steel or magnetic steel, with internal teeth. Various arrangements of windings on the stator teeth create armature poles for multiple phases of output voltage. The low loss magnetic core allows for efficient operation at high shaft speed and allows for efficient AC excitation of the rotor for special applications.

Micromachined Semi-encapsulated Spiral Inductors For Microelectromechanical Systems (MEMS) Applications

Abstract: Semi-encapsulated spiral inductors for microelectromechanical systems (MEMS) applications have been designed, fabricated, and characterized using micromachining and electroplating techniques. The inductors are fabricated on a Pyrex glass wafer using a simple three mask process and have an area of 4 mm by 4 mm. Devices consist of electroplated copper conductor lines with width 50 /spl mu/m, thickness 25 /spl mu/m, and spacing 30 /spl mu/m; they are semi-encapsulated with an electroplated Ni-Fe (81%/19%) magnetic core. At the low frequency of 10 kHz, the inductance of the devices was measured as 1.5 /spl mu/H, while they exhibited a low resistance of only 3 ohms. Their low resistance and reasonably high inductance makes them ideal in MEMS applications as either sensors or actuators.

Three-dimensional magnetic field analysis of electrodes for VCBs [vacuum circuit breakers]

Abstract: This paper describes the application of three-dimensional magnetic field analysis, including eddy current effects on the axial magnetic field electrodes of vacuum circuit breakers. The accuracy of the analysis is verified with both basic and full models of the electrodes. The analytical results were compared with measured values obtained by a Hall sensor system. The effect of the electrode slit length and the electrical conductivity of the contact on the magnetic flux density and phase difference was analyzed with the full model. The magnetic field in the gap was simulated when the arc ignites between the electrodes. These results demonstrated that the magnetic design of the electrodes can be carried out on an engineering workstation.

Magnetic field properties of Bi-2223/Ag HTS coil at 77 K

Abstract: High T c superconducting (HTS) (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10+ x Ag clad multifilament wire, is used to prepare a HTS coil. Magnetic field behaviour of the HTS coil is studied at 77 K operation. Experiments carried out include magnetic field measurements of the HTS coil, DC magnetic field, AC magnetic field, and critical current ampere-turns when used as a magnetic core bias winding. The magnetic field distribution of the HTS coil is also investigated for use at 77 K with the anisotropic HTS wire. The experimental results and analysis provide basic information for design and operation of a HTS coil made from the present HTS (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10+ x Ag clad wire.

Rotor of motor

Abstract: PROBLEM TO BE SOLVED: To effectively arrange the magnets within a limited space to improve the performance and effectively use reluctance torque, by arranging in almost in parallel a pair of permanent magnets provided opposed with each other between neighboring magnetic poles to keep the predetermined interval with respect to the normal of rotor. SOLUTION: A rotor is composed of a rotor iron core 26 formed by laminating a plurality sheets of rotor steel plate, inserting holes 36 to 39 provided to the rotor iron core 26 along the axial direction of rotating shaft and four sheets of flat type permanent magnets 40 to 47 inserted to the inverting holes 36 to 39. A pair of permanent magnets 40 to 47 provided opposed with each other between neighboring magnetic poles 28, 29 30, 31 are arranged in parallel keeping the predetermined interval with respect to the normal of the rotor. Therefore, magnets can effectively be arranged in the limited space to improve the characteristics and magnetic path of the predetermined interval can be attained to effective use the reluctance torque.

Analysis and design of ferrite cores for eddy-current-killed oscillator inductive proximity sensors

Abstract: Finite element modeling of ferrite cores used in the design of eddy-current-killed oscillator inductive proximity sensors was performed. Based on contemplation of the practical operation of the sensors, ferrite core geometries were compared with a reference core by the eddy-current power loss in a metal target at a fixed distance from the face of each transducer. Several of these cores were experimentally evaluated for sensing distance to verify the results of the simulation. It was observed that, for fixed coil, fixed target distance, and given target, the low-frequency sensing distance of a particular transducer is approximately proportional to the fourth root of eddy-current power loss in the target.

Magnetron sputtering cathode with magnet disposed between two yoke plates

Abstract: A method of coating a substrate by magnetron cathode sputtering includes a sputtering cathode having pole shoes and being arranged in a vacuum chamber. A target and a magnetic field are provided in an area of the surface of the target and the magnetic field is varied stepwise and/or continuously to displace the plasma radially such that the erosion groove is likewise displaced radially. The variable magnetic field is generated by coils between the back surface of the target and a yoke plate while a static magnetic field is gernated by an annularly arranged magnet in the area of the yoke plate and a target space between the target and the substrate is shielded by means of an iron core which also increases the field strength of the variable magnetic field.

High-frequency power transformer model for circuit simulation

Abstract: A model for the circuit simulation of transformers used in high-frequency power processing is proposed. Many important transformer effects are combined in a single formulation. An Atherton-Jiles model with improved minor-loop handling ability is employed to simulate the hysteresis effect in the magnetic core. Eddy currents and skin and proximity effects are simulated by dynamically approximating the field and flux distributions in the entire structure. Leakage fluxes, capacitive couplings and the influence of temperature on electric and magnetic materials are also included. The parameters needed for simulation are magnetic material characteristics, available in data sheets, core geometry and winding geometry. The model was implemented (built) in the source code of SPICE3.