Showing papers on "Magnetic circuit published in 1983"

Combined position sensor and magnetic motor or bearing

Abstract: A combined magnetic sensor and actuator device for applying a magnetic force to a magnetizable body and for sensing the distance between the device and the magnetizable body. The device includes a magnetizable pole piece separated from the magnetizable body by gaps. The pole piece, gaps, and magnetizable body form a magnetic circuit with the gaps preferably being the major reluctance of the circuit. Separate means are provided for generating a relatively large time-varying magnetic actuating flux in the magnetic circuit and for generating a relatively small time-varying magnetic sensing flux in the magnetic circuit. Each magnetic flux follows a flux path, such that the two flux paths have at least a portion in common. Detection means measure the relatively small magnetic flux in the magnetic circuit, and thereby measure the distance between the device and the magnetizable body.

A new zero-ripple switching DC-to-DC converter and integrated magnetics

Abstract: A new switching dc-to-dc converter is synthesized which consist of the least number of storage elements (inductive and capacitive) and switches, and yet truly emulates the ideally desired dc-to-dc transformer having both input and output currents as pure dc quantities with no ripple. This result was facilitated by implementation of a new concept termed integrated magnetics, which leads in some special switching structures to the integration of otherwise independent and separate magnetic components (inductors and transformers) into a single magnetic circuit.

Moat-guarded Josephson SQUIDs

Abstract: We report experimental investigations of a simple structure, called a moat, which significantly reduces the probability of flux-trapping in Josephson SQUIDs. Proper operation of Josephson logic and memory circuits requires that the SQUIDs be free of stray magnetic flux that may become trapped in the superconducting groundplane upon cooling through the critical temperature. The problem is particularly severe for so-called holey SQUIDs which rely on holes in the groundplane to obtain suitably large device inductances. Moats are rectangular channels in the groundplane surrounding the SQUID's which provide preferred sites for trapping flux, thus preventing such flux from coupling to the SQUID. We have measured the effectiveness of moats by monitoring the flux trapped in the moats and comparing it to the flux trapped in the associated SQUID as a function of applied field. The number of flux quanta in the moat is determined by measuring the shift of the threshold curve of a two-junction SQUID coupled to the moat. The data indicates that at fields on the order of a mG, moats reduce the sensitivity of holey SQUIDs to trapped flux by at least several orders of magnitude. As the chips are cooled through T c , transient magnetic fields are produced in the metallic sample holder parts surrounding the chip by thermal-gradient-induced EMF's. The effects of such magnetic fields on the flux trapping behaviour of the SQUIDs are also reported.

Electro-magnetic alignment assemblies

Abstract: This invention is directed to electromagnetic alignment apparatus, which is particularly adapted, among other possible uses, for use in aligning the wafers in a microlithography system, said apparatus comprising in combination a first magnetic circuit having a plurality of elements including a first magnet; a second magnetic circuit having a plurality of elements including a second magnet; the second magnetic circuit being disposed in spaced relationship with respect to the first magnetic circuit; a movable structural component adapted for mounting an object thereon; one element of each magnetic circuit being fixedly attached to the movable structural component; first and second current carrying coil assemblies mounted in the first magnetic circuit; the second coil assembly being disposed at an angle with respect to the first coil assembly; third and fourth current carrying coil assemblies mounted in the second magnetic circuit; the fourth coil assembly being disposed at an angle with respect to the third coil assembly; and control apparatus for controlling the flow and direction of the current through the coil assemblies, respectively.

Permanent magnet rotor with saturable flux bridges

Abstract: A rotor structure for a permanent magnet generator, or PMG, includes a plurality of spaced apart magnets and magnetic circuit elements in series with the magnets on the rotor to act as flux limitation means to thereby limit the output voltage of the permanent magnet generator at low current levels.

Arcing and Interruption Phenomena in AC Vacuum Switchgear and in DC Switches Subjected to Magnetic Fields

Abstract: Vacuum interrupters are extensively used in contactors, motor starters, tap-changers, distribution apparatus, and metalclad switchgear. The present paper reviews this growing technology with descriptions of the internal components of a vacuum interrupter, a brief history of the development steps, and a discussion of the range of application of these devices. The basic physical properties of cathode and anode spots are described, together with a discussion of the arcing and interruption phenomena which occur in vacuum interrupters during an ac wave. This includes a description of arc initiation, the high current arc mode, current zero phenomena, and dielectric recovery plus voltage withstand. The influence of electrode material and electrode configuration is included. The paper concludes with a brief description of dc applications for vacuum interrupters, where axial magnetic fields have been used in conjunction with current counterpulse in tokamak circuits, and transverse magnetic fields have been used to commutate current from vacuum arcs to parallel circuits. The extensive references have been selected to give the reader a broader overview of vacuum switching technology.

Resiliently suspended stator for a dynamo-electrical synchronous machine

Abstract: The magnetic circuit (6) of the stator is suspended from resilient suspension bars (26) which are welded both to floating stiffening rings (30) that are firmly mounted on the magnetic circuit, and to some of the stiffening rings (20) of the outer sheath (18). Other casing stiffening rings (22) have openings to allow the suspension bars to pass freely therethrough, and are equipped with stops to limit rotation of the stator in the event of an electrical fault. There are thus two paths for transmitting force between the magnetic circuit and its surrounding sheath, one of which can be optimized for damping the vibrations of normal use, while the other can be optimized for avoiding damage under fault conditions.

Coupled Inductor and Integrated Magnetics Techniques in Power Electronics

Abstract: Energy storage and power processing with magnetic devices is more efficient if the separate inductors and transformers are integrated into a single magnetic structure. The origins and main results of the coupled-inductor and integrated magnetics concepts are reviewed.

Thin-film magnetic writing head with anti-saturation back-gap layer

Abstract: Apparatus for producing a magnetic image in a magnetic image storage medium. The apparatus includes a thin-film magnetic web (12) with a pole-defining face and a second thin-film blanket (24) magnetically spaced from the first magnetic web and having a second surface defining a second pole face. Spaced from the pole faces is a diamagnetic spacer (16) which forms a special back gap in the magnetic circuit. An electrical coil (20b) sandwiched between the two magnetic materials induces flux in them. The spacer (16) may extend normal to the flux path beyond the effective flux paths otherwise existing in the web and blanket.

Magnetic field simulation from a voltage source

Abstract: A finite-element program has been developed to digitally simulate the dynamic response of solenoids to a specified voltage trace. The evolution of the magnetic field is modeled complete with eddy currents and saturation effects. The motion of the solenoid's plunger in response to mechanical and magnetic forces is incorporated into the solution for the magnetic field. Moreover, these effects are coupled with the electrical driving circuit whose inductance is unknown (and varying).

Current balancing for battery strings

Abstract: A battery plant is described which features magnetic circuit means for balancing the electrical current flow through a pluraliircuitbattery strings which are connected electrically in parallel. The magnetic circuit means is associated with the battery strings such that the conductors carrying the electrical current flow through each of the battery strings pass through the magnetic circuit means in directions which cause the electromagnetic fields of at least one predetermined pair of the conductors to oppose each other. In an alternative embodiment, a low voltage converter is associated with each of the battery strings for balancing the electrical current flow through the battery strings.

A numerical method for calculation of electromagnetic circuits using the tableau approach

Abstract: This paper presents a new method for solving the transient response problems of electric and magnetic circuits coupled with each other. Using the nodal analysis method the electromagnetic circuits are represented in a tableau form, T.X = b, and are calculated to obtain the geometrical distribution and the time dependence of circuit variables. The tableau form is a matrix equation, and the equation consists of two parts. The one is an equation of electric circuits related with external and eddy currents, and the other is an equation of magnetic circuits given by the geometrical discretization of machines. Taking the hysteresis and the eddy-current effects into account, the transient response of an iron cored reactor is calculated numerically to demonstrate this method. Numerical and experimental results are compared and satisfactory agreement is found.

New design method of permanent magnets by using the finite element method

Abstract: A new method for determining the shapes and sizes of magnets which produce the prescribed flux densities by using the finite element method has been developed. In this paper, the new technique is explained briefly, and then the finite element formulation for non-linear analysis is derived. Finally, the usefulness of the technique is shown by applying this method to the design of magnetic circuits.

Design Considerations in Multi-Output DC-DC Converter with Magnetic Amplifiers

Abstract: Multiple output dc-dc converters, that take advantage of cross-regulation, are useful power supplies for electronic equipment which require several regulated voltages with good isolation. However, since regulation errors are contained in the cross-regulated outputs, they should be stabilized to obtain a precisely regulated output. Magnetic amplifiers are suitable for this purpose, but no quantitative design method has yet been fully established. This paper proposes utilization of magnetic amplifiers to compensate for cross-regulation errors in the multi-output dc-dc converter, and describes SR optimum design conditions presenting a suitable cross-sectional area and number of turns for the SR. Further, it is also clarified that SR core can be reduced in size by utilizing an amorphous core and increasing the operating frequency.

Computer Models of Hysteresis in Mechanical and Magnetic Components

Abstract: There is a strong analogy between mechanical structural elements and magnetic circuit components which can be extended to include hysteretic energy losses associated with yielding in mechanical systems and saturation in magnetic components. Procedures for developing finite state models of hysteretic components are presented using a small number of basic elements. Using bond graph techniques, it is shown that, when dual structural models are used, elements may be assembled in arbitrary numbers to achieve any desired accuracy without problems of derivative causality. The reason for the dual structure can be seen from physical reasoning. The shape of the hysteresis curve for magnetic materials generally requires more elements for a given degree of approximation than the shape of the typical mechanical hysteresis curve.

Electromagnetic contractor with flux sensor

Abstract: A flux sensing device, preferably a Hall effect sensor (58) is mounted in an air gap (56) in the magnetic circuit of an electromagnetic contactor. The sensor provides an output signal indicative of the magnitude of flux in the magnetic circuit. The output signal can be used to regulate the electrical excitation of the coil (10) of the contactor. In one form a linear signal from the sensor (58) is amplified by a linear amplifier and controls a current source feeding the coil. In another form the sensor (58) is a digital flux sensor which switches between first and second states with changes in the sensed flux, and the excitation coil current from the current source (60) is switched in response to the digital state.

Variable flux permanent magnets electromagnetic machine

Abstract: The rotor or stator of an electro-magnetic machine, such as an electric motor, having permanent magnets is provided with auxiliary permanent magnets which are relatively positionable to provide an external magnetic flux path during normal operation of the machine and an internal magnetic flux path to enable the rotor to be readily separated from the stator for the purpose of maintenance or repair work. The invention also contemplates, for example, fine speed calibration, through variation of the intensity of a magnetic field during running of electro-magnetic machines such as DC motors.

Effects of magnetic characteristics of materials on the iron loss in the three phase transformer core

Abstract: The finite element method has been applied to clarify the relation between magnetic characteristics of the electrical steel and power transformer iron losses. Three material constants which represent the magnetic characteristics are used for this study. The computed results have contributed to understanding of factors which increase the transformer iron losses.

Experimental Verification Of Three-Dimensional Analysis Of Leakage Magnetic Fields In Large Power Transformers

Abstract: In a previous paper by the first author, a three-dimensional analysis for the calculation of the leakage magnetic field in power transformers was presented. The experimental verification of this analysis is the subject of this paper. Extensive comparisons between calculated and measured values of flux densities in the winding of an experimental three-phase shell form transformer are presented. The results as well as the agreements and deviations obtained are discussed in light of the ultimate objective of accurate determination of various transformer performance parameters. The close agreements obtained verify the accuracy of the method of calculation as well as the validity of the experimental and measuring techniques. The results also demonstrate that accurate determination of losses, circulating currents, short circuit forces, impedance, shielding requirements and other performance parameters is possible only through three-dimensional calculations of the leakage magnetic field in the transformer.

Earth fault circuit breaker responding also to direct fault currents

Abstract: of EP00164581. Fault current safety switch for disconnecting users even in the case of direct current fault currents, which operates with a tripping device, a switch lock and a summation current transformer (1) which comprises a first secondary winding (3) connected to an oscillator (9) and comprises a second secondary winding (4) connected to an excitation winding of a magnetic tripping device, characterised in - that the magnetic tripping device (10) has two excitation windings (16, 17), a first (16) and a second (17), on arms of its yoke (12), - that the first excitation winding (16) is connected to the oscillator (9), the second excitation winding (17) being connected to the second secondary winding (4), and - that the two excitation windings (16, 17) are tuned to one another in such manner that on operation of the oscillator (9), the magnetic fluxes produced by said excitation windings in the magnetic circuit of the magnetic tripping device (10) in the fault current free state, are unidirectional and opposite in relation to one another.

Variable reactance inductor with adjustable ranges

Abstract: A discharge lamp ballast for stabilizing wattage input into a discharge lamp at different levels in two or more ranges comprises a magnetic core forming a closed magnetic circuit. A main winding on the core may be used alone or with an extended winding switched in series, and be connected in series with the lamp across an alternating current source in a lamp operating circuit. A control winding on the core has a triac connected across it to vary the current and thereby the wattage supplied to the lamp in the operating circuit. A pair of gapped shunts, one located between the control winding and the extended winding, and the other between the extended winding and the main winding, assure a proportionally greater control effect on the series reactance in the lamp operating circuit when the extended winding is switched in than when it is not.

Dual-path electromagnetic actuator for a high performance magnetic disk drive

Abstract: The design and analysis of a dual path electromagnetic actuator for a high performance magnetic disk drive is presented. Experimental results for E-shape actuators with a single or dual path magnetic field are also presented. In comparison with the conventional single path actuator, this new design has distinct advantages such as (1) elimination of the solenoid effect resulting in equal force constants in the push and pull directions, (2) evenly distributed flux lines with better orientation, (3) reduction in flux leakage so that the actuator can be placed in closer proximity to the disk.

Magnetic differential position sensor

Abstract: To determine the relative position of two objects, for example pistons (16, 22) respectively responsive to the deflection of a brake pedal (10) and actual braking pressure of a wheel of a wheel brake (18) in an automotive power assisted braking system, a core having salient poles, such as an H or E core, has windings wound on the core, coupled to sensing circuits which determine the inductance of the winding, upon placement of short-circuit rings, or coupling magnets on, or adjacent to the core to affect the magnetic circuit, and hence the inductance of the winding. The inductance of the winding can be sensed by connecting the core in an oscillatory circuit (FIG. 3B), applying alternating current thereto, respectively inversely phased (FIG. 4B) and determining phasing of output, or connecting the coils in a multivibrator circuit (FIG. 4C), the output, upon balance of the magnetic circuits, being a pulse train of unity duty cycle upon balance; or connecting the coils to a supply voltage such that the magnetic circuit in a center leg of the salient poles will be in opposition, and sensing the flux in the center leg by an additional sensing coil (FIGS. 5A, 6), which flux will be exactly balanced if the magnetic circuits of the respective salient poles are balanced due to uniform position, or uniform change of position, of the respective magnetic elements, such as magnets or short-circuit rings.

Horn speaker with reduced magnetic flux leakage

Abstract: By adding a secondary magnetic piece with a partially open magnetic circuit to the front surface of a yoke connected to a primary magnetic piece, the magnetic flux leakage from the main magnetic piece is reduced on one hand and the magnetic flux extending across a magnetic gap is intensified through formation of a favorable magnetic field. This horn speaker is particularly useful in a ship where a horn speaker as an alarm is often required to be placed near magnetically sensitive equipment such as a compass.

Electric stepping motor.

Abstract: The motor according to the invention comprises a disc-shaped rotor with multipolar permanent magnetization along an annular area and a stator comprising a plurality of magnetic circuits (9, 10,...) arranged so that the magnetic field is comprised within the two cylindrical face portions based on the magnetized annular area and located on either side of the rotor. Means for compensation of the harmonics of the current-free torque and of the current torque are provided, as well as the arrangement of magnetic pick-ups (25, 26). The invention applies to industrial synchronous motor which may operate as stepping motors.

Electric circuit breakers having fast short circuit response

Abstract: A thermal magnetic circuit interrupter with instantaneous short circuit current response utilizes a hook-shaped contact arm pivotally mounted on the operating mechanism at the end of the contact arm most distant from the contact. A saddle-type torsion spring proximate the pivot end of the contact arm provides adequate contact pressure while allowing the contact to immediately respond to magnetic forces generated under short circuit conditions. The immediate separation of the contacts reduces the current let-through the operating mechanisms while the tripping mechanism operates to trip the breaker.

Zero-quantum superconducting magnetic shielding apparatus and method

Abstract: The design of a new superconducting magnetic shield is described, together with a method for achieving a final state in which no magnetic flux quanta are trapped in the shield's central region. The magnetic shield consists basically of a specially designed superconducting cylindrical tube, equipped with electrical and magnetic devices to remove flux quanta trapped during cooldown. An electrical current is applied along the length of the tube to cause mutual annihilation of trapped vortices and antivortices in the tube's central region and thus to remove flux quanta transverse to the cylinder axis. A parallel applied magnetic field then moves an appropriate number of vortices and antivortices from tube-end reservoirs to opposite ends until no longitudinal flux quanta thread the tube. Typical dimensions, various materials requirements, and conditions for successful operation of the magnetic shielding apparatus are discussed.

Assembling and magnetizing method for magnetic circuit

Abstract: PURPOSE:To enable to perform a complete magnetization in a weak magnetic field by a method wherein, in the assembled body of the magnetic circuit formed by providing a permanent magnet having R (at least a kind of rare-earth element containing Y), B and Fe as main ingredients, the permanent magnet is magnetized maintaining the specified range of high temperature. CONSTITUTION:An Fe-B-R permanent magnet consists of main ingredient of R of 8-30atm%, B of 2-28atm% and Fe of 42-90atm%, and its main phase consists of a pressure crystal phase, and Nd and Pr are used as R. A magnetizer has a plurality of magnetic poles whereon an electromagnetic coil 5 is wound around, a magnetic circuit consisting of an Fe-B-R magnet 1, a yoke 2 and a center pole 3 is provided thereon, and a high temperature is maintained in a high-temperature furnace within the temperature range of 50-140 deg.C, and the Fe- B-R magnet 1 is magnetized by applying a current to the magnetizer. As the above is assembled and magnetized in the high temperature atmosphere of 140 deg.C or below, the stabilization of heat ageing and the magnetization can be accomplished in one process.

High speed rotating disc type generator for high magnetic field

Abstract: A high magnetic field generator based on a new idea is described in this paper. The principle of the generator is different from those of previously published or tested. The fundamental principle of generating a high magnetic field is that the magnetic flux induced by an electromagnet with an iron core is concentrated by eddy currents on a rotating conductive disc and is compressed to high magnetic flux density on the hole surrounded with four discs. The energy for concentrating a magnetic flux is fed from the kinetic energy of rotating discs. Therefore, the generator is non-destructive and has only a relatively small electric source. The high magnetic field has a long pulse duration.

Magnetic shield for rotary actuator in a magnetic disc device

Abstract: A rotary actuator for a magnetic disc device for swinging a head arm to position a magnetic head mounted at an end of the head arm to a desired track of a magnetic disc is disclosed. Magnetic shield plates are provided to a magnetic circuit assembly which forms a voice coil motor together with a moving coil mounted at a rear end of a head carriage which supports the head arm in order to prevent leakage magnetic fluxes created in the vicinity of a permanent magnet of the magnetic circuit assembly from reaching the magnetic head.