Showing papers on "Magnetic circuit published in 1984"

Two-Dimensional Field Analysis of Cylindrical Machines with Permanent Magnet Excitation

Abstract: The design of the magnetic circuit of permanent magnet machines differs from that of conventional wound field machines mainly due to the low magnetic permeability of the magnets. A two-dimensional field analysis is presented which takes the magnet leakage, the distribution of magnet MMF along its height, and the changing magnet width into consideration. The fundamental component of flux calculated by the model is compared with results obtained by finite element analysis for different magnet configurations covering a practical range of magnet dimensions. A comparison of machine performance predicted using this method with test results is also given.

Planar Circuit Analysis of Microstrip Radial Stub

Abstract: Microstrip radial line stubs are analyzed using a planar circuit technique and characterized for design purposes. Experiments performed on various structures are in excellent agreement with the theory.

Magnetic recording medium

Abstract: PURPOSE:To improve the efficiency of vertical magnetic recording, by connecting a vertical anisotropic thin-film track for recording and a high-magnetic- permeability magnetic thin-film track for reflux connected to the bottom part of the vertical anisotropic magnetic thin-film track to a track on a magnetic disk surface CONSTITUTION:The main magnetic pole 6-1 of a magnetic head 6 corresponds to a track of a vertical anisotropic magnetic thin film 1-4-1 for recording and its subordinate magnetic pole 6-2 corresponds to a track of a high-magnetic-permeability thin film 1-4-2 for reflux of a magnetic recording medium 1; they are slid by the magnetic head simultaneously Therefore, when the exciting coil 7 of the magnetic head 6 is excited, magnetic flux passes through a magnetic head yoke and the main magnetic pole 6-1 to excite the track of the vertical anisotropic magnetic thin film 1-4-1 for recording and then passes through the high-magnetic-permeability thin film 1-2, high-magnetic-permeability magnetic thin film 1-4-2, subordinate magnetic pole 6-2 of the magnetic head, and magnetic yoke to constitute a closed magnetic circuit directly, so recording and reproduction with remarkably high efficiency are performed

Variable reluctance actuator having position sensing and control

Abstract: A controlled force variable reluctance actuator. A variable reluctance actuator having a moving element operated by a solenoid is provided in which the current in the solenoid is controlled by a signal representative of the flux density in the magnetic circuit of the actuator. The signal is produced by a Hall effect device placed in the magnetic circuit. Preferably, the Hall effect device controls the current in the solenoid by controlling its duty cycle; however, continuous control of the current may also be employed. Alternative embodiments are provided for a constant force actuator, an actuator whose force-displacement characteristic is altered, and an actuator in which the force may be selectively controlled. An embodiment is also provided for selectively controlling the position of the moving element based upon measured electric and magnetic parameters of the actuator.

Nonlinear complex finite elements analysis of electromagnetic field in steady-state AC devices

Abstract: A nonlinear analysis of electromagnetic devices supplied by a sinusoidal alternating current or voltage source is presented. In numerous apparatus like motors, generators, traveling field induction furnaces, etc., the saturation effect must be taken into account for the design but does not affect widely the waveform of the current which may be assumed sinusoidal. We shall present here a complex analysis based on the assumption of sinusoidal fields on two-dimensional geometries in Cartesian or axisymmetric coordinates.

Determination of AC magnetic power loss of electrical steel sheet: Present status and trends

Abstract: A brief survey of the status of work in the higher induction and frequency ranges is given and recent papers on the measurement of rotational losses are reviewed. The determination of the magnetic losses in alternating fields is considered, in partucular regarding the performance of those magnetic circuits most widely used in loss measurements. New and revised data contribute to the elucidation of the systematic errors of the Epstein square. The Epstein samples and plate samples, both of various materials, were used for measurements with single sheet testers, whereby the field strength was determined both from the magnetizing current by means of a precision resistor and direct, using field sensing coils. From these results conclusions for the appropriate value of the effective magnetic path length can be drawn. The electric power measurement particularly as regards digital procedures, calibration and uncertainties is briefly discussed.

On a Magnetic Damper Consisting of a Circular Magnetic Flux and a Conductor of Arbitrary Shape. Part I: Derivation of the Damping Coefficients

Abstract: Theoretical results for finding the damping coefficients of a magnetic damper consisting of a circular magnetic flux and an arbitrarily shaped conductor have been obtained. In the analysis the exact solution in polar coordinates for the governing equation of the electromagnetic fields is utilized. The boundary condition for arbitrarily shaped boundaries of the conductor is satisfied directly by means of the Fourier expansion collocation method. To discuss the accuracy of the present approximate results, the analysis also has been performed on damper consisting of a circular flux and a circular conductor. The comparison between the present results and the exact ones for the typical damper shows very good agreement.

Method for sensing and controlling the position of a variable reluctance actuator

Abstract: A controlled force variable reluctance actuator. A variable reluctance actuator having a moving element operated by a solenoid is provided in which the current in the solenoid is controlled by a signal representative of the flux density in the magnetic circuit of the actuator. The signal is produced by a Hall effect device placed in the magnetic circuit. Preferably, the Hall effect device controls the current in the solenoid by controlling its duty cycle; however, continuous control of the current may also be employed. Alternative embodiments are provided for a constant force actuator, an actuator whose force-displacement characteristic is altered, and an actuator in which the force may be selectively controlled. An embodiment is also provided for selectively controlling the position of the moving element based upon measured electric and magnetic parameters of the actuator.

Solenoid-controlled valve

Abstract: A solenoid-controlled valve of the present invention is provided with a valve housing having first, second and third ports, first and second movable members housed in the valve housing to freely move along its longitudinal axis and is made of magnetic material, and a magnetic circuit for magnetically attracting the first and second movable members independently in order to move them in the direction of the axis. The magnetic circuit includes a solenoid, a magnetic flux by-pass for by passing the second movable member, and a magnetic resistance attached to that portion of the magnetic circuit which is by-passed by the magnetic flux by-pass. The solenoid-controlled valve further has first and second valve members, which are actuated by the movement of the first and second movable members in the direction of the axis to independently open and close the first and second ports.

Magnetic head and method of fabricating same

Abstract: A magnetic head core and a method of fabricating same, wherein a magnetic circuit is constituted by a pair of magnetic films having a V-shaped cross section which face each other at each protrudent section through the gap material. The cross-sectional portion of the V-shaped film is exposed to the surface facing the magnetic recording medium. The protrusions of the magnetic film pair have tip planes parallel to each other and substantially perpendicular to the moving direction of the magnetic recording medium. The tip plane has a width defined by the line of intersection between the plane and the surface facing the magnetic recording medium in correspondence to the recording track width. At least one of the magnetic films has a window for winding an excitation coil. The magnetic film is formed on the non-magnetic protection member having a V-shaped protrusion. The magnetic head has superior recording and reproducing characteristics in a wide frequency band with less rubbing noise, high wear-resistivity and high productivity, and operates without the pseudo gap effect. The magnetic head core is fabricated through the steps of forming a coil winding groove in the gap forming plane of a non-magnetic core block, forming a number of parallel grooves perpendicularly to the winding groove so that a number of V-shaped protrusions are produced, forming a magnetic film on the surface of the protrusions, forming a gap plane after the magnetic film has been coated with non-magnetic material, and splitting the block and then combining the two core blocks to complete a magnetic head core.

Magnetic head comprising a core formed of small and large thin film patterns

Abstract: A thin film magnetic head comprising a magnetic core of accumulation layers forming a magnetic circuit and including at least two layers of magnetic film with a particular magnetic characteristic. The constitution of completely covering a magnetic film with a small pattern by a magnetic film with a large pattern makes the edge part smooth because the end of the underlying magnetic film is covered with the upper magnetic film. This edge-smoothing effect appears most pronounced in a manufacturing method in which electrodeposition is used for the formation of magnetic films. By sequentially forming the magnetic films from that of a smaller pattern towards that of a larger pattern, the film formation proceeds at step parts such as end parts of the underlying magnetic films due to the levelling action which is inherent in the electrodeposition method. Such a film formation realizes extremely smooth shielding and yet the pattern formation can be carried out by a single step of photoresist coating to shorten the production process.

Application of magnetic wedges to large motors

Abstract: Although high output power density can be achieved in electrical machines by increasing airgap flux density, this also increases tooth ripple flux density with a subsequent increase in pole surface loss. This loss, however, can be reduced with magnetic wedges. This paper describes the calculation of pole surface losses and ripple flux density, and the effect of magnetic wedges on the characteristics of practical motors is shown experimentally.

Printing head for dot printer

Abstract: PURPOSE:To attain to enhance the efficiency of a magnetic circuit and to increase the speed of a printing head by reducing leak magnetic flux without damaging the effect of a core-type magnetic circuit, by providing a magnetic leak part for leaking magnetic flux flowing to an armature and a yoke to the circumferential direction of a core with respect to the inner peripheral surface thereof. CONSTITUTION:A magnetic leak part 12a for reducing a demagnetizing current is provided to the inner peripheral surface of a core 12 constituting a magnetic circuit in opposed relation to a yoke 11 and an armature 3 so as to generate magnetic leak (a) to the circumferential direction of the core. By this constitution, the generated magnetic leak (a) is originally different from leak magnetic flux and this leak magnetic flux is suppressed as low as possible and, in its turn, the enhancement of suction force is achieved. Because the magnetic leak (a) opens a driving leaf spring 5, a current is made to flow to a demagnetizing coil 8 and an open current necessary for negating the energy possessed by a permanent magnet 10 is reduced. If the quantity of the magnetic leak (a) becomes too large, the suction force characteristic of the magnetic circuit is lowered and, therefore, otpimum magnetic leak quantity is set by adjusting the distance (l) between the leak part 12a and the yoke 11/armature 13 and the opposed area (s) of the leak part 12a.

Design of polyphase motors with PM excitation

Abstract: Design guidelines are presented for synchronous motors with permanent magnet (PM) excitation. A general model is established and the dependence of the electric and magnetic loadings on the angle between the armature and field excitations is put in evidence. For this angle there exists an optimal value which yields maximum torque for maximum allowable flux density in the teeth. Another value yields the minimum volume for the permanent magnets. These values guide the selection of the operating point of the motor and its preliminary design. It is found that, when the pole pitch exceeds a certain value, the magnet requires more space than a current carrying winding.

Heating cooking appliance having weight detecting function

Abstract: A heating cooking appliance in which a Roberval mechanism, which produces a change in the vibration frequency in accordance with the weight of the food to be heated, is incorporated in a turntable, and the vibration of the turntable is transmitted to the outside of the heating chamber through a magnetic coupling using a magnet to detect a magnetic signal outside the heating chamber. In order to positively pick up the magnetic signal, a yoke is employed in the magnetic circuit and a detecting coil is arranged near the magnet by raising the heating chamber bottom plate, thereby tightening the magnetic coupling. Further, in order to eliminate electromagnetic wave noise, etc., a filter circuit is provided to ensure exact picking-up of the vibration signal. In order to avoid an influence on the magnetic signal of other magnetic field producing devices, the measurement is made either while such devices are not in operation or by using an added magnetic shielding means. Then, the weight of the food is calculated in accordance with the detected vibration frequency and the heating time, heating output and heating pattern are controlled in accordance with the calculated weight of the food. This cooking appliance is featured particularly in enhancing convenience of using the appliance and in realizing finely adjustable cooking.

Device for measuring direct currents

Abstract: 1. Device for measuring direct currents comprising a measuring coil (1), which carries the direct current to be measured, a magnetic circuit (2) with an isthmus (3), a compensation coil (4), which carries the current reflecting the current to be measured, an indicator coil (5), which leads to an amplifier (6, 22) driving the current in the compensation coil (4), and a magnetisation coil (7), which is supplied with an alternating current, characterised in that the magnetic circuit (2) is composed of a parallel circuit of magnetic conductors in the region of the isthmus (3), wherein one of those (8) carries the magnetisation coil (7) as well as the indicator coil (5).

Electromagnetic actuator comprising at least two distinct magnetic circuits

Abstract: An electromagnetic actuator comprises two armatures which are relatively movable to define a stroke and which form a main magnetic circuit the reluctance of which is variable between the ends of the stroke. A secondary magnetic circuit is formed between the armatures and its reluctance is also variable between the ends of the stroke, the variation being different to that of the first circuit to allow the relationship between the force of the actuator and the stroke position to be trailored to suit different requirements.

Lightweight cladding for magnetic circuits

Abstract: A magnetic cladding device having a constant exterior magnetic potential al to a magnetic potential at a point between either end of an active magnet for enhancing the active magnet's field and reducing magnetic field leakage comprising a magnetic cladding circumscribing an active magnet and having a magnetic axis transverse to that of the active magnet.

Magnetic head for perpendicular magnetization

Abstract: MAGNETIC HEADS FOR MAGNETIC 10 PERPENDICULAR INVENTION INCLUDES FIRST AND SECOND PAIR OF BLOCKS 10A, 10B MADE EACH BODY NON-MAGNETIC 11, 11 AND ONE HEAD Ferromagnetic 12, 12 ASSEMBLY EACH OTHER THIN Ferromagnetic 13 FILM MAKING SANDWICH BETWEEN FIRST AND SECOND BLOCK, COIL 17 ROLLED AROUND THE THIN FILM AND CYLINDER BLOCK FIRST AND THIRD BLOCK Ferromagnetic 14 FIXED IN THE FIRST BLOCK TO OPPOSE THE THIN FILM AND SECOND BLOCK. PLAY MODE, MAGNETIC CIRCUIT IS CLOSED SHAPE THROUGH THE MIDDLE OF MAGNETIC RECORDING THE THIN FILM, THE HEAD OF THE FIRST BLOCK AND THIRD BLOCK.

Electromagnetic Coupling From Power Lines and Magnetic Field Safety Analysis

Abstract: The first objective of this paper is to describe the relationship between electric and magnetic field coupling to metallic circuits. Conditions for which one or the other dominates are outlined. Following this, a discussion of why the longitudinal electric field (LEF) can be used to calculate magnetic coupling is given. The second objective of this paper is to summarize the differences between electric and magnetic coupling safety analyses. Specifically, the reasons why magnetic coupling effects are inherently more difficult to predict are discussed. Finally, the questions are outlined which must be answered so that safety assessment can be reconciled with the small number of complaints attributed to magnetic field coupling.

Photo-magnetic recorder

Abstract: PURPOSE:To obtain a compact and light-weight optical head and at the same time to improve the generating efficiency of magnetic field by providing a magnetic circuit for application of vertical magnetic field of a recording medium having the length covering the scan region of the optical head at a position opposite to the optical head and holding the recording medium. CONSTITUTION:A magnetic flux phi flows to a magnetic path consisting of a magnetic pole 5 and a yoke 7 when an exciting coil 6 is conducted electricity. This flux phi cuts a recording medium 1. When the distance S is reduced satisfactorily between the pole 5 and the medium 1, it is possible to impress a magnetic field having the direction vertical to the medium 1 which is opposite to the tip of the pole 5. In this case, the intensity of the magnetic field can be increased by the tip part 5a of the pole 5 into a wedge form. In addition, the excited current quantity is also reduced by providing a yoke 7. At the same time, the magnetic fields having approximately equal intensity can be obtained if an optical head 2 has an access to any position since the pole 5 has such length that can cover the access range of the head 2.

Optical pickup device

Abstract: PURPOSE:To reduce the overall weight and capacity of an optical head and at the same time to eliminate the evil effect of generation of heat, by protruding a ferromagnetic substance extended from a part of a magnetic circuit which drives an objective lens against a recording medium and therefore ensuring the effective use of the leaked magnetic flux of the magnetic circuit to obtain a magnetic field. CONSTITUTION:A projection part 32 of a ferromagnetic substance is fixed at the tip of a yoke 7b of one side and opposite to the recording surface of a recording medium 11. Thus the magnetic flux leaked from a magnetic circuit is led to a place nerar the medium 11 via the part 32 as shown by an arrow 33, and the magnetic field is intensified on the medium 11. Therefore a magnetic field of the direction where the magnetization is easily produced acts on the medium 11 by the leaked magnetic flux of the magnetic circuit applied via the part 32. Thus it is possible to record the information as conventional with irradiation of a light beam. In such a way, a magnetic field is applied to the medium 11 by means of a magnetic flux leaked from a magnetic circuit which drives an objective lens 2. Thus, a magnetism applying device consisting of an electromagnet, a coil, etc. is eliminated. Therefore the overall weight and capacity of an optical head including an optical pickup device can be greatly reduced.

Performance Parameters of Power Transformers Using 3D Magnetic Field Calculations

Abstract: Today's challenges in the design of power transformers necessitate, among other things, very accurate calculation of the performance parameters of the transformer (such as losses, impedance, shielding, s.c. forces, etc.), reduction of load losses, and preventing overheating and local hot spots. Presented in this paper are theoretical and experimental studies conducted to precisely assess the need and projected benefits of these calculations based on the 3D determination of the leakage field of the transformer. Also presented are results of the already achieved objectives in winding loss calculation and magnetic shielding design.

Magnetic ring for free piston rectilinear generators

Abstract: The generator comprises at least one coil surrounded by a magnetic circuit of an inductor for taking-off electrical power. The magnetic circuit forms a variable gap with a reciprocating mobile part moving between two positions. The mobile reciprocating part is made in the form of a magnetic ring made by sheets of ferro-magnetic material having a uniform thickness and width and being radially positioned. The distance between the sheets at the proximity of a residual gap is such that ferro-magnetic material in area of the residual gap represents from 50 to 80% of the sheets in the magnetic circuit of the inductor.

Magnetic‐field analysis of ferrofluidic seals for optimum design

Abstract: Ferrofluidic devices have found applications in laser systems, high‐vacuum equipment, computers, loudspeakers, inertia dampers, and motors. With the technique of magnetic‐fluid sealing, one is called upon to produce custom solutions for complex and diverse seal problems, many of which may be characterized by very hostile environments, wide temperature ranges, and intense radioactive conditions. In designing a magnetic circuit for a magnetic‐liquid seal, a number of factors, such as the size of the available envelope, pressure differential across the seal, chemical compatibility with various environments, and proper selection of permanent and soft magnetic materials need to be considered for achieving the most cost‐effective solution while meeting the entire range of requirements for any specific application. In order to evaluate flux leakage and fringing while accounting for nonlinear characteristics of magnetic materials, it becomes necessary to resort to numerical techniques to determine the effect caus...

Magnetic head having an integrated recording and playback head and an erasure head

Abstract: The present invention relates to a magnetic head, which can form guard bands on a magnetic recording medium and which is especially suitable for magnetic discs, and a fabrication process thereof. The magnetic core of the present invention includes a recording and reproduction head core (31) and an erasure head core (32) which is integrally joined in series to the head core (31) for forming guard bands. Magnetic circuits are constructed of metallic magnetic materials (34), (34'), (35) and (35') formed on non-magnetic members (33) and (33'). As a result, a recording medium having high coercive forces can be recorded while the track width is reduced and the fabrication is facilitated with a high accuracy.

Single-phase step motor

Abstract: A single-phase step motor comprises a stator having a coil and a magnetic circuit composed of a core and a plate having a hole in which is disposed a rotor equipped with a permanent magnet. The plate has a slot in the area of the hole, whose width and the position of the axis line thereof are determined by the magnetic asymmetry of the stator poles, sufficient to produce required driving and positioning torques of the motor.