Showing papers on "Magnetic circuit published in 1978"

Analysis of the efficiency and inductance of multiturn thin film magnetic recording head

Abstract: Expressions for the flux in a multiturn thin film head are derived and used to obtain equations for the efficiency and inductance as a function of film structure and permeabilities.

Magnetic viscous damper

Abstract: Disclosed herein is a rotary viscous damper using a magnetic fluid as the damping medium. The damper comprises a permanent magnet rotor enclosed in a magnetically permeable housing. The magnetic fluid fills the space between the rotor and the housing and is held in place using magnetic forces generated by the magnet rotor. The torque of damper may be varied by changing the viscosity of the magnetic fluid or the level of the magnetic flux in the magnetic circuit.

Electromagnetic power generator

Abstract: An electromagnetic power generator for installation in the interior of a vehicular tire, working on the principle of deriving energy from the fact that a portion of the tire becomes flattened once every revolution, causing a change in the length of the corresponding chord. A small closed magnetic circuit is alternately opened and closed by this movement, by means of a flexible strap coupled between the tire interior and the magnetic circuit. The circuit is reclosed by magnetic attraction.

Hall effect ignition system housing

Abstract: A housing contains a circuit board having a Hall effect sensor attached thereupon and a magnetic circuit positioned to provide magnetic flux through the Hall effect sensor. The magnetic flux through the Hall effect sensor is interruptable by a high permeability vane moving through an air gap in the magnetic circuit, activating the Hall effect sensor to provide timing signals for an automotive ignition distributor system. The base of the housing has locating bosses for positioning the housing on a swing arm of the ignition distributor which is pivotable about the axis of the distributor shaft. Mutually perpendicular surfaces contained within the housing provide reference locations for positioning the circuit board with respect to the housing. The housing has respective portions for containing a flux concentrator and a magnetic and pole piece assembly on opposite sides of the circuit board. Adhesive means fix the magnetic circuit elements and the circuit board in position so as to provide an air gap between the circuit board and the magnet and pole piece assembly for passage of the moving vane, which interrupts the magnetic flux passing through the air gap and through the Hall effect sensor.

Method of making an inductive circuit incorporated in a planar circuit support member

Abstract: A planar support member for an electric circuit, eg a printed circuit board, wherein at least a region of the support member includes magnetic material through at least a part of its thickness A magnetic circuit is made in this material by forming at least one opening through it The support member is then coated with insulative material and conductor paths are made on both faces of the support member by conventional techniques for such members These paths include a winding disposed around a core part of the magnetic circuit with alternate half turns being formed on opposite faces and interconnected by through plating The inductive circuit thus formed may constitute an inductor, a transformer or a relay

Transformer with parallel magnetic circuits of unequal mean lengths and loss characteristics

Abstract: An electrical transformer having an electrical winding and a magnetic core having two parallel magnetic circuits having unequal mean lengths. The shorter of the parallel magnetic circuits is constructed of a magnetic material which exhibits a lower loss characteristic than the magnetic material used in the longer of the parallel magnetic circuits, at like levels of induction.

Contribution to the study of leakage fields at the ends of rotating electrical machines

Abstract: A method is described for calculating the axial leakage field of the end regions of rotating electrical machines. The method subdivides the problem into the component fields of the magnetic sources that contribute to the axial field. The total field is then found by superposing these component fields. The method is compared with the traditional approach of analysing the magnetic field of electrical machines in terms of magnetic circuits. Measurements are presented of the field in air outside the laminated core of a slotless, cylindrical model. These measurements are in good agreement with the predictions of the method. The method is then used to consider qualitatively the behaviour of the field inside a laminated core. Conclusions are also drawn about the way in which the leakage field will alter with changes in the dimensions and operating conditions of the core.

Motor using Hall effect elements

Abstract: A motor using Hall effect elements is disclosed, in which a disk-shaped multi-pole magnet which is circumferentially divided into a plurality of magnetic poles each magnetized in an opposite polarity to its adjacent magnetic poles is attached to a rotary shaft and a magnetic circuit is constituted by the multi-pole magnet and a yoke plate disposed to face the multi-pole magnet. A pair of Hall effect elements are disposed within a magnetic field of the multi-pole magnet to detect positions of the respective magnetic poles of the multi-pole magnet. Output voltages from the pair of Hall effect elements are supplied to a pair of drive coils, respectively, to generate driving magnetic fluxes therein. A pair of pole pieces are mounted on the yoke plate to face the pair of Hall effect elements, respectively. The pair of pole pieces are axially movable to allow adjustment of spacings between the respective pole pieces and respective Hall effect elements so that magnetic flux densities supplied to the pair of Hall effect elements can be adjusted.

Speed insensitive wheel detector

Abstract: An apparatus for detecting the presence and/or direction and/or velocity of a moving ferromagnetic element is provided. A sensing coil is placed in coupling relationship with a bi-stable ferromagnetic wire to provide a signal in response to a change in polarity of the core of the bi-stable wire. The core polarity changes in response to element presence as the element constitutes a magnetic shunt causing a change in magnetic flux density and/or direction in the air gap of a magnetic circuit in which the bi-stable wire is situated. The sensor is substantially insensitive to element velocity. Modified structures provide for fail-safe operation.

Performance prediction of a wide-angle limited-motion rotary actuator

Abstract: A doubly excited, doubly salient, concentrated winding type of rotary actuator structure is examined. Neglect of iron-member reluctances predicts a flat torque characteristic over the normal limited range of movement. In practice, a flat characteristic is not achieved. The reason for this is shown, by analysis and measurement, to be due to the significance of the iron reluctances both before and after the onset of magnetic saturation in the iron. A lumped magnetic circuit approach is used in conjunction with the rate-of-change-of-coenergy method to predict the torque characteristic under linear conditions. Beyond saturation, an iterative method is used to find the fluxes and hence the torque characteristic. Correlation between predicted and measured torque/angle curves is reasonably good.

Moving permanent magnet limited motion actuator

Abstract: A limited motion actuator which utilizes a moving permanent magnet as an armature. The drive is provided by the simultaneous repulsion and attraction of the movable permanent magnet within stationary coils. The magnetic circuit is formed to allow one pole of the armature to be simultaneously repelled from the coil of like polarity and attracted to the pole of opposite polarity. The preferred magnetic circuit configuration consists of two poles and a magnetic return path, which forms two additional poles. The movable permanent magnetic armature is always located within the regions of the coil poles thus allowing accurate control of the driving forces in both forward and reverse directions over the complete armature cycle.

Deleterious mechanical vibrations from dynamic loudspeaker offset by additional dynamic device

Abstract: A dynamic loudspeaker comprises first and second device means each having a coil disposed in a magnetic gap formed in a magnetic circuit, a vibratory member driven by a first drive means, and a massive member opposingly disposed to the vibratory member and being driven by a second drive means, whereby reaction force generated by said vibratory member is substantially eliminated by reaction force of said massive member.

Method for forming a magnetic core for a linear compressor

Abstract: A method for forming a magnetic core for the magnetic circuit of a linear-motor compressor suitable for use in a refrigerant system. The compressor includes a conical armature which reciprocates in a complementary air-gap under the influence of an electromagnetic circuit and a pair of linear complementary return springs connected to the armature between the compressor piston and outboard bearing. The electromagnetic circuit includes a pair of abutting convoluted loops of spirally wound magnetic strip material with a conical air-gap fabricated in the area of abutment. The magnetic core is formed by forming a pair of stacks of magnetic strips having diverse lengths, bending each stack to form a generally C-shaped core section having a generally semi-circular air-gap space defined by the ends of the strips, fastening the C-shaped stacks in opposed abutment to form a generally cylindrical air-gap, and then machining the air-gap into the desired conical shape.

A new bridge-connected magnetic circuit using amorphous magnetic core and its applications

Abstract: This paper is a description of the operating principle and the circuit configuration of a new bridge-connected magnetic circuit proposed by the authors. This magnetic circuit is constructed by a toroidal amorphous magnetic core with high permeability and a usual magnetic core with low permeability and has a number of excellent characteristics in the operation. Using this circuit the authors made various interesting devices used as the instrument and the control.

Magnetic means for determining partial pressure of oxygen particularly in underwater breathing apparatus

Abstract: A paramagnetic oxygen sensor wherein a reference chamber is oscillated into and out of an air gap of a magnetic circuit by means of a piezoelectric bender bar. The oscillating reference periodically displaces the ambient gas under measurement in the air gap and causes a varying flux in the magnetic circuit which is sensed, amplified and provided as an output signal indicative of the partial pressure of oxygen of the gas mixture.

Hook shaped magnetic pole generator

Abstract: PURPOSE: To reduce magnetic flux leaked between magnetic poles with an adhesive containing hard magnetic material filled between the poles and a space formed by the pole and a field coil to fasten thereof. CONSTITUTION: A thermosetting adhesive 15 containing powdered ferrite or the like is filled into a space 13 between hook-shaped magnetic poles 4 forming a main magnetic circuit of leaked magnetic flux and a space 14 formed by the poles and a field coil 5 and olidified by heating. In the hard magnetic material power, magnetism is generated by flowing current through the field coil 5 in the opposite direction of the normal field current. With such an arrangement, the magnetic material is magnetized in the direction as indicated by H1 and H2. This works so as to offset the leaked magnetic fluxes ϕ1 and ϕ2 whereby the leakage thereof can be reduced. COPYRIGHT: (C)1979,JPO&Japio

Cooling and cooling circuits for electric motors

Abstract: Though thermal considerations are one of the major limitations to the output obtainable from electrical machines, the thermal design of machines and their cooling circuits seems seldom to be accorded quite the attention that is normally directed to the electrical and magnetic circuits. There are various ways in which the designer of an electric motor handles the losses occurring in the different parts of the machine: generally, by dissipation from the surface, but also by conduction from areas that are difficult to cool adequately to those where this is easier to achieve, and, where appropriate, by using the thermal capacity of the machine to even out peak or cyclic thermal loads. The superior dissipation obtained by blowing air over a surface rather than relying on natural convection and radiation results in all but the smallest motors relying on some form of forced cooling, in which cooling air is blown over the surfaces to be cooled by shaft-driven fans. Though the cooling-air paths of electric motors are often complicated by the need to cool all the many component parts of the machine in which losses occur and therefore in which heat is generated, nevertheless an application of quite simple considerations of fluid flow yield acceptable methods of estimating the resistance of the air paths. Similarly, the behaviour of the common types of fans used on electrical machines is developed, and, by way of illustration, graphical solutions are indicated for a few typical motor cooling circuits.

Permanent magnet generator

Abstract: A permanent magnet generator is provided which is intended for use in close physical relation to an associated main generator, such as an aircraft generator. To prevent severe modulation of the output voltage of the permanent magnet generator due to stray magnetic fields from the main generator, short-circuited windings are provided encircling the magnetic circuit of the permanent magnet generator in a manner to minimize the effect of such stray magnetic fields.

Safety device for lifting magnets

Abstract: A safety device for lifting magnet has sensor means responsive to flux produced by the device in the magnetic circuit including the body to be lifted, a transducer responsive to the lifting tension produced by the device together with a signal translation circuit effective to compare signals from the sensor and from the transducer and to provide an output indicative of a safety margin between lifting tension and the field available for lifting.

A Method to Measure Magnetic Fields Accurately Using Ampere's Law

Abstract: A proposed method to measure magnetic fields is described, and a simple demonstration of the new method has been performed. A derivation of the equation used to calculate the field is presented, and some ofits implications are discussed. The objective of further experiments is to apply the technique to the measurement of the gyromagnetic ratio of the proton (?p) to an accuracy near 1 part in 108, using a precision solenoid whose departures from ideal are small.

Robust polyphase transformer

Abstract: A polyphase sector type transformer includes one magnetic core ring per phase, each of which has two rectilinear sides which are adjacent to each other. Each rectilinear side of one magnetic core ring is disposed contiguously with one of the rectilinear sides of an adjacent core ring whereby each magnetic core ring occupies a sector of the magnetic circuit of the transformer. Each pair of contiguous rectilinear sides is threaded through a coil of the transformer said coils comprising a high tension winding of trapezoidal cross-section and a low tension winding of rectangular cross-section. Each magnetic core ring is symmetrical about the plane of symmetry of the two coils which it threads; comprises an assembly of two generally arcuate parts arranged to facilitate threading of the coils on the rectilinear sides before the said core parts are joined by adhesive, the parts being separated along a plane perpendicular to the said plane of symmetry by sawing and; is made of a binder-impregnated, laminar stack of magnetic sheets of at least two different widths such that two contiguous rectilinear sides of two adjacent cores threading a single coil combine to give a magnetic circuit within the coil having a right cross-section which includes steps at the changes from one thickness of sheet to another and thereby forms a closer approximation to an ellipse than would a rectangular made from magnetic sheets all of the same width.

Differential transformer pick=up for straight or angular movements - has HF supplied primary winding and secondary winding supplying signal voltage

Abstract: One of the windings consists of two coils connected in opposition. A moving magnetic shunt (5) is connected to the moving member whose movement is to be recorded or captured. A magnetic circuit is closed in such a way that the field generated by the primary winding (2) flows through the secondary winding (3, 4) completely. The magnetic circuit is rectangular and the two coils of the twin-coil winding are positioned on two opposing arms of the circuit. The second winding is, in this case, on one of the other two arms of the circuit, parallel to which moves the shunt.

Magnetic-technical system with a magnetic circuit comprising at least two magnets

Abstract: Magnetic-technical systems useful in magnetic separators for separating magnetic materials from liquid or dry materials containing magnetic particles. The magnetic technical systems are characterized by possessing one magnetic circuit comprising at least two magnets and at least one operating air gap, and being further characterized by the fact that the circuit containing the magnets is closed and that within said circuit there is an operating gap in relation to two mild iron or steel parts which in each case are arranged between two interconnected homopolar magnets.

Self travelling type record player

Abstract: PURPOSE: To apply servo to the motor and control the speed with high performance by providing the travelling member with the magnetic flux detecting means such as magnet and coil and the signal obtained by disposing a plurality of slits radially on the magnetic plate. CONSTITUTION: While the car body 2 travels on the record disc 1 and gradually moves inward, the magnetic flux of the magnet 8 reaches the mgnetic disc 27 through the record disc 1. The magnet 8 passes the respective slits 29 of the disc 27 and the upper portion between the respective slits alternatingly, so that the magnetic resistance in the magnetic circuit changes alternatively. Accordingly, there is obtained a signal having frequency proportional to the speed of the car body 2 from the coil 24. This signal is added to the speed control circuit of the motor and the speed of the motor 4 is controlled. Therefore, the reproducing needle 26 constantly traces the speed of the car body 2 at a predetermined angular speed. The speed of the car body is controlled. COPYRIGHT: (C)1980,JPO&Japio

Pulsed excitation alternator

Abstract: Alternator having a pulsed excitation. Means are provided to supply short current pulses into the pick-up coils at a suitable time so to magnetize the circuit. As a consequence the shape of the magnetic circuit can be simplified and the weight of iron and copper can be reduced.

The geometry of regulating transformers

Abstract: Ferroresonant, ballast, and current-limiting transformers are similar in geometxy. Optimization of weight, losses, or cost can result in different choices for the shape (core or shell) and proportions of the lamination. In the ferroresonant transformer, the problem of saturation losses, noise and stray flux can be alleviated by altering the geometry to produce a magnetic circuit with nonuniform flux density.

Electromagnetic device of the flat package type

Abstract: A miniaturized electromagnetic device is disclosed, which is applicable to an electromagnetic relay of the flat package type. The electromagnetic device comprises a magnetic core having the configuration of the capital letter H, a coil wound round the magnetic core, and a pair of magnetic members for alternatingly forming two closed magnetic circuits in cooperation with said magnetic core, said magnetic members being formed in one-piece with the aid of connecting members of non-magnetic material, one of said magnetic members including a permanent magnet, and each tip of said magnetic member confronting the corresponding tip of said magnetic core and the clearance therebetween being changeable by the magnetic force generated therebetween as said coil is energized.

Eddy current losses in solid iron pieces under three-dimensional magnetic field

Abstract: This paper deals with a method to compute eddy losses in the massive magnetic pieces of electrical machines when the magnetic field near the material surface has three components. The flux outside the massive pieces is computed assuming that there are no eddy currents. This is normally satisfactory because the very weak coupling between magnetic and non-magnetic areas. Time dependence is neglected and only peak values are considered. Inside the material, the eddy currents concentrate the flux in a very thin skin depth. The local losses depend on that flux or the associated magnetic field. They are analytically calculated assuming a one-directional geometry. Time dependence, which may be sinusoidal or not, and the iron saturation is now considered. The internal flux path is determined, taking into account the iron piece shape, by solving a two-dimensional quasi-Poissonian equation. Computed and experimental figures of magnetic field and losses are compared at the same locations in a 20 MVA transformer.

Magnetic circuit for magnetic bubble

Abstract: PURPOSE:To obtain a uniform magnetic field distribution in the space enclosed by the inner wall of the circular core and the shielder, by winding the wire to the circular core and then conducting the current of 90 deg. different phase to the coil to generate the rotary driving magnetic field. CONSTITUTION:Shield substance 5 composed of the conductor materials such as copper, aluminum and the like is provided as if it included circular core 3 and coil 4. With conduction of the AC current to coil 4, the magnetic field produces the overcurrent to substance 5. This overcurrent flows so as to produce the magnetic field identical to that produced with the infinite value of the core height in the space enclosed by the core inner wall and the shield case. Thus, a uniform magnetic field can be obtained at any area within the space. At the same time, coil 41 and 42 are wound so that their magnetic fields may be orthogonal to each other, that is, coil 41 and 42 are mede to be proportional to 1costheta1 and 1sintheta1 respectively.

Driving device for electronic time piece

Abstract: PURPOSE: To reduce battery capacity by controlling the energy of permanent magnet by the switching of magnetic circuit and by utilizing the energy of rotor driving by constituting the driving device with rotor, stator, permanent magnet, and magnetic resistance switching element. CONSTITUTION: When the rotor 6 is at rest, no input voltage is applied to the magnetic switching elements 4a to 4d consisting of magnets wound with coil and loop form of magnetic fluxes 9a, 9c, 8a, and 8b generate in the permanent magnet 7 and the rotor 6. And, when the rotor is drived, current flows in the coils 4a and 4d and thereby magnetic fluxes generate in the states 10a and 10b, the stator 5 is magnetized to the polarity, as shown in Fig., and the rotor 6 is turned through 180° by a repulsion between the rotor 6 and the N-pole. Then, by the one second later driving of the rotor 6, the magnetic switching elements 4c and 4b are saturated with magnetism, the N and S poles of the stator 2 generate on the opposite side, and the rotor 6 is drived. Thus, the magnetic energy of the permanent magnet 7 can be utilized as energy for rotor driving by being controlled by the switching of magnetic circuit. COPYRIGHT: (C)1979,JPO&Japio