Showing papers on "Electromagnetic coil published in 1980"

Implant telemetry system

Abstract: An externally generated myriametric frequency magnetic carrier signal is resonantly reflected by a tuned coil in an implant. The lagging phase angle of the reflected signal is modulated at very low power by varying the impedance across the tuned coil in accordance with a data input signal. An external phase shift demodulator recovers the transmitted data. To assure adequate coupling between the external unit and the implant, the output level of an external phase comparator must exceed a given threshold to signify "acquisition" before data is transmitted from the implant. In a preferred embodiment, a shunt circuit across the tuned coil is opened and closed in accordance with a digital input signal generated by the implant. The external telemetry unit preferably includes a coaxially spaced triple coil assembly. The middle coil transmits the carrier. The outer pickup coils are balanced to minimize carrier reception. For two-way communication an IR transmitter is added to the coil assembly. During acquisition, the output of the tuned coil is used to turn on a dormant IR receiver in the implant. Light emitting diodes are preferably mounted in an array on the face of the coil assembly surrounded by an optional reed switch coil for multimode telemetry in the programmer.

Device applicable to direction finding for measuring the relative orientation of two bodies

Abstract: A magnetic coupling device in which two assemblies of three coils are attached respectively to two mechanically independent bodies and form a radiator assembly and a sensor assembly. Each assembly defines a cartesian coordinate frame and is associated with a switching circuit controlled so that the radiator coils are excited successively and separately by the same alternating-current wave and so that the sensor coils are connected separately and successively to processing circuits during each excitation stage of a radiator coil. The processing circuits comprise a synchronous demodulator, a coherent integrator and a control loop for reducing the induced signal received to zero and measuring the corresponding field component. This measurement is performed by an ancillary computer which determines the Euler angles.

Feedback control type shock absorbing suspension system

Abstract: A feedback control type shock absorbing suspension system is inserted between a body including a vibration source and a foundation for suspension of the body. The absorbing system includes a suspending spring mechanism. A sensor mechanism detects velocity of relative movement between the body and the foundation. A cylinder-piston mechanism includes a cylinder connected to one of the body and the foundation and a piston connected to the other of the body and the foundation. Magnetic fluid or powder is held between the inner wall of the cylinder and the outer wall of the piston. An exciting coil generates magnetic flux for magnetizing the magnetic fluid or powder. An electric circuit applies to the exciting coil a control voltage which corresponds to the detected value of the sensor mechanism. The vibration-damping force between the cylinder and the piston is controlled by magnetizing the magnetic fluid or powder.

The development and applications of a wide band electromagnetic sounding system using a pseudo-noise source

Abstract: A very wide band (0.03 Hz to 15 kHz) electromagnetic (EM) system has been developed. It was used over the band 1 Hz to 10 kHz to determine the electrical structure of the earth’s crust from depths of a few meters to over 40 km. A direct current of from 1 to 5 A was reversed through a long wire bipole transmitter in a pseudo‐random binary sequence (PRBS). Depending upon the frequencies selected, a sensitive one‐component flux gate magnetometer or an air‐core coil was used to monitor temporal changes in the vertical component of the magnetic field at a recording site. The measured signal was crosscorrelated digitally in real time with an exact copy of the transmitted waveform in order to obtain a good signal‐to‐noise ratio at distances up to 5 times the length of the bipole. The output crosscorrelogram was deconvolved from the system input, the autocorrelogram of the transmitted waveform, using a Wiener least‐squares filter to give the impulse response of the earth. This was then transformed into frequency ...

Miniature motor coil

Abstract: Spiral type first and second coils of the same shape and size are arranged opposite one another on both surfaces of an insulating sheet, the insulating sheet is made by piling and bonding two insulating films to each other using a bonding agent, the inner ends of the first and second coils which are opposite to each other are connected to each other via the insulating sheet, the outer ends are so connected that all coils are connected in series, and terminals are provided on both ends of the series connection.

Plural sensor magnetometer arrangement for extended lateral range electrical conductivity logging

Abstract: A method of well logging in petroleum exploration and apparatus for use in the method is described An improved magnetometer is disposed in a well bore to provide indications of the distribution, filimentation, and distortion of a controlled current flow within adjoining strata of interest The current flow is excited by a distant alternating source located at the surface or at other boreholes, and perturbations in the current flow and accompanying magnetic field caused by the electrical characteristics of the adjoining strata are registered by the magnetometer The magnetometer comprises two pairs of elongated U-shaped cores of laminated, high-permeability metal, adjacent portions of each pair being surrounded by a sensing coil The coil outputs are fed to surface equipment for detection and analysis

Electric propulsion and braking system for automotive vehicles

Abstract: An electric propulsion and braking system which includes a plurality of high-speed, dc commutatorless motors each coupled to a wheel of an automotive vehicle through an associated fixed-ratio mechanical transmission. Each motor includes a field winding, an armature winding, and a commutation circuit for the armature winding. During propulsion, each commutation circuit is enabled and, during braking, each commutation circuit is disabled. Control of the amount of propulsion and braking is afforded by varying the dc source voltage across each commutation circuit and by varying the field current in each field winding. The dc source voltage across each commutation circuit is varied by connecting the commutation circuits and a plurality of main electrical energy sources in selected series, series/parallel, and parallel combinations. The field current in each field winding is varied by connecting the field windings with an auxiliary electrical energy source in selected series, series/parallel and parallel combinations, and by duty-cycling the selected combination. The various series, series/parallel and parallel combinations are selected by, and the duty-cycling of the selected field winding combination is controlled by, a microprocessor receiving signals representing the magnitude of electrical energy transfer between the main electrical energy sources and the motors, the position of an acceleration pedal, the position of a brake pedal, the velocity of the vehicle, the dc source voltage across each commutation circuit, and the armature voltage across each armature winding.

Electro-acoustic planar transducer

Abstract: An electro-acoustic transducer using thin, lightweight, planar diaphragms driven by strategically located, coil-driven, high-energy, permanent magnets. A framework maintains the diaphragms in substantially co-planar relationship a predetermined distance from and parallel to a rear support wall. The diaphragms include at least one hinged woofer diaphragm and a foam-supported tweeter diaphragm. The small, high energy movable permanent magnets are attached to the rear surface of each movable diaphragm. Cooperating with each movable magnet is a respective, stationary electromagnetic coil with a crossover network directing the incoming signal to the appropriate coils, thereby placing the magnets and attached diaphragms into cooperating fore and aft motion. The frontal acoustical waves produced by each woofer constructively interfere to augment low frequency response. The tweeter construction provides wide frontal dispersion of high frequency acoustical waves. Woofer backwaves are attenuated before emerging along the rear support wall and the tweeter backwave is vented into a rear isolative chamber.

Estimation of transformer winding temperatures and coolant flows using a general network method

Abstract: The windings of large modern transformers are generally cooled by pumping oil through a network of ducts in the winding. The resulting value of the hottest conductor temperature and the position it occurs in the winding are important parameters in the design and operation of a transformer. There is a standard method for estimating the value of this hot spot but there is very little information on the position at which it occurs. Also, devices have been developed which when inserted in a winding will measure the local temperature. These instruments could be used to measure the hot-spot temperature of a winding in a transformer on load. However, it would obviously be advantageous if the position of the hot spot could be estimated so that the device could be installed in the optimum position. The work reported here attempts two things: first, to improve on the standard method for estimating the winding temperature distribution and hot-spot temperature and secondly to estimate the position of the hot spot. The computer program developed to do this can be used to estimate the flows, fluid temperatures and boundary temperatures for any network of flow paths. However, only its application to a transformer is considered here. The method used to obtain the required predictions is described, and estimates are presented of the winding temperature distribution for a particular design of transformer operating with a steady load.

Magnetic field concentration means and method for an implanted device

Abstract: A magnetic field concentration means and method for use in conjunction with an implanted device responsive to an externally generated magnetic field More specifically, a magnetic field concentrator is disclosed which includes a metallic slug located between a magnetic field generator and a magnetic pick-up coil contained in the implanted device The metallic slug concentrates magnetic lines of flux at the pick-up coil In a specific embodiment, the implanted device is an intracranial pressure monitoring device (ICPM) which is located within an orifice formed in a recipient's skull The magnetic field concentrator is positioned within the orifice and directly above the ICPM, thereby concentrating magnetic flux lines at the ICPM Two configurations of the slug are disclosed, one being in the form of a cylinder and the other being in the form of a truncated cone In another application of the concentrator, a bandage or other suitable holding means positions the slug externally to the implanted device, thereby again concentrating magnetic lines of flux at the implanted device

Alternator for wind generator

Abstract: An alternator for wind generator use employing a pair of stators having a rotor mounted therebetween in planar coaxial relationship. The stators have radially slotted coil forms integral therewith in which coils are wound in a serpentine fashion. The rotor is provided with an aluminum rim slotted in a radial manner inwardly of its periphery to hold permanent magnets, which magnets through the aid of the rim concentrate eddy currents in the coils in an improved manner.

Winding method for an electrical generator and generator manufactured by the method

Abstract: A three-phase stator winding of an alternator is divided into six partial windings. Each partial winding, regardless of electrical phase, is wound starting at the slot immediately adjacent to the slot wherein the last previously wound winding was started and in the same winding direction. The first partial windings for the subsequent phases are also inserted in the slots in the same direction as the first partial winding for the first phase, so that connecting arcs are formed on the same side of the stator as was the case for the first phase. The second partial windings for each phase are placed so that the connecting arcs form on the side of the stator opposite to that on which the first connecting arcs were formed. The winding starts and winding ends of each of the partial windings associated with a given phase are connected so that the partial windings are connected either in series or in parallel. The so-formed series or parallel circuits are then connected to form either a Y or a Δ configuration.

Motor with a disk rotor

Abstract: Slow-running brushless d.c. motors with a disk rotor, a flat air gap and an iron-free stator winding made up of a number of coils are particularly suitable for direct drive of sound recording and reproducing equipment at a highly steady and controlled speed. The iron-free coils are arranged in a one-layer winding arrangement connected to form a plurality of phase windings, each comprising a pair of magnetically oppositely poled coils and rotor position sensing means, such as a Hall generator, are provided for controlling the currents in the phase winding so as to obtain four-current pulses per rotor rotation angle of 360 electrical degrees and to set up a rotary magnetic field driving the permanent magnet rotor. Two sets of coils are shown in the stator winding, each set comprising at least one pair electrically connected with each other and oppositely poled and spaced from each other by (2n+1)·180 electrical degrees, where n is a low positive integer. Double wound coils are shown with the two wires of the coils of a set being wound bifilarly and connected to form two-phase windings per set, with the width of the individual coils substantially greater than 180 electrical degrees. Embodiments illustrated show the disposition of coils and sensors for various cases in which the rotor has from three to seven pairs of poles.

Finite element formulation and analysis of three dimensional magnetic field problems

Abstract: A three dimensional finite element formulation and algorithm for the solution of 3-d magnetic fields was developed. The method is presented here with applications to determination of local flux densities in a 3-d field pattern, as well as global energy calculations of an air cored coil. The results compare well with closed form solution results. Experimental test data of the coil inductance is in agreement with finite element results. The development represents a new technique which is a potentially very powerful tool in many practical applications.

High frequency electrosurgical instrument for an endoscope

Abstract: A high frequency electrosurgical instrument for an endoscope comprises a flexible tube which has at a distal end portion a pair of wire guiding holes spaced from each other in the axial direction of the tube. In the distal end portion of the tube a flexible coil is inserted, which extends at least between the wire guiding holes. An electrode wire extends in the tube from a distal end of the flexible coil, comes out of the tube through the wire guiding hole located adjacent to the distal end of the tube, reenters the tube through the wire guiding hole located adjacent to the proximal end of the tube and through a pair of turns of the coil which are located near the latter wire guiding hole, extends through the tube to the proximal end of the tube, and is connected to a high frequency power source. The electrode wire is reciprocable within the tube, except for its distal end portion. The flexible coil prevents said electrode wire from cutting the tube to form a slit extending from either wire guiding hole and prevents said tube from collapsing.

Self-sustaining solenoid

Abstract: A self-sustaining solenoid which is adapted so that when applying an operating current to a coil, a moving iron core disposed in the coil is attracted into contact with a fixed receiver. A magnetic yoke is provided to extend between the fixed receiver and the end portion of the moving iron core projecting out of the coil, and a permanent magnet is disposed on the magnetic yoke at least at one end in the direction of movement of the moving iron core. When the moving iron core is held in contact with the fixed receiver, magnetic fluxes emanating from the permanent magnet mostly pass through the moving iron core, the fixed receiver and the magnetic yoke, and even if the operating current is cut off, the moving iron core is retained in contact with the fixed receiver. A magnetic gap is provided through which the magnetic fluxes of the permanent magnet mostly pass when the moving iron core is out of contact with the fixed receiver, and magnetic flux resulting from the application of the operating current pass through the magnetic gap.

Multi frequency eddy current test apparatus with intermediate frequency processing

Abstract: An eddy current test apparatus and method in which multiple sequential test frequencies are employed. The voltage induced in a sensing coil at said test frequencies are multiplexed and frequency translated to provide a single frequency for processing. The apparatus employs a single channel to process the induced voltages.

Use of motor winding as integrator to generate sawtooth for switch mode current regulator

Abstract: A stepper motor for use in peripheral devices such as electronic printing terminals has its coils selected for activation by selection circuitry, with its power provided by a switch mode current regulator. The switch mode regulator utilizes the selected motor winding as the storage element of the regulator and the voltage ramp derived from the current flow through the motor coil itself for comparison with a reference voltage. The output of the comparator circuit controls the state of a latch which has a fixed frequency clock input. The frequency of the latch output is fixed, but the on time and off time of the latch varies in accordance with the output of the comparator. A comparator and latch circuit therefore form a pulse width modulator which then regulates the on and off time of the switching regulator power transistor.

Induction disk motor with metal tape components

Abstract: An induction motor of the squirrel cage type is disclosed. The stator body and rotor body of the motor are each disclosed as being made of a coil of concentric layers of a thin metal tape which is slotted to receive the rotor and stator windings. The motor is similar to a conventional disk type motor except that the secondary, instead of being a solid copper or aluminum disk, is a coil of concentric turns of notched metal tape which improves the efficiency by reducing the effective air gap. A method of manufacture of the coil of tape is disclosed wherein identical notches are formed in the tape with a progressively increasing spacing between the notches which permits the notches to come into radial register with one another to form a slot in the end of the stator or rotor body.

Induction heating coil

Abstract: An improved flat induction heating coil for a cooking apparatus of the type in which an electrically conductive cooking utensil is heated according to the principle of electromagnetic induction. To provide a substantially uniform magnetic flux density distribution in the induction coil constituting a part of the cooking apparatus and, hence, a uniform temperature distribution across the bottom of the cooking utensil, a refractory insulating material is wound adjacent inner turns of the coil to provide a comparatively larger winding pitch for said inner turns than for outer turns. This arrangement makes for a flattened temperature profile and eliminates an uneven cooking of food.

Flat electric coil

Abstract: A miniaturized electric coil having a low self-capacitance comprises a bottom conductor pattern provided on a substrate, an insulating intermediate layer and a top conductor pattern which is connected to the bottom conductor pattern via windows in the intermediate layer. The bottom and top conductor layers each comprise n single spiral-like paths. The inner end of the first spiral of the bottom conductor layer contacts the outer end of the first spiral of the top conductor layer, while the inner end of the first spiral of the top conductor layer in its turn contacts the outer end of the second spiral of the bottom conductor layer, and so on.

Multistage electromagnetic accelerator

Abstract: A multistage electromagnetic accelerator in which energy is serially induced in stages of parallel rail having serially segmented segments or stages utilizing a high DC current source, circuit breakers, and induction coils with both primary and secondary windings to produce ultra high exit velocity in an armature and projectile which are slidably disposed between the parallel rails

Brushless DC motor

Abstract: A brushless DC motor having a rotor magnet magnetized to provide a sinusoidal magnetic field and two-phase stator windings at positions which differ from each other by an electrical angle which is an odd multiple of 90° is provided with a drive circuit comprising a signal generator with an output having a frequency determined by the rotational speed of the rotor, and a memory having stored therein digital information data converted from sampled values of a sinusoidal signal free of distortion The digital information data stored in the memory is read out therefrom by the output of the signal generator in synchronism with the magnetic field from the rotor magnet, and such read-out information data is employed to determine currents flowing through the stator windings so that torque ripple is substantially eliminated

Accelerometer and evaluation circuit

Abstract: The combination of an accelerometer and an evaluation circuit are disclosed for controlling a safety device in an automobile. The accelerometer includes a pair of electromagnetic circuits having a sensor coil and arranged at an angle other than 180° relative to each other. A movable member is positioned within the angle and is deflected upon acceleration, due to inertia, to induce electrical voltages in the coils. The magnitude of the induced voltages are a function of the direction of acceleration. The evaluation circuit includes a directional discriminator connected to the coils to generate a signal to actuate the safety device in response to a voltage with a predetermined polarity occurring in at least one of the sensor coils, when the other voltage is zero or of the same polarity. The angle between the electromagnetic circuits is chosen to generate the first signal only in response to accelerations occurring within a desired directional sector. An acceleration level discriminator and an integrator, for generating signals representative of the speed change of the accelerometer, may also provide control signals.

Ink jet recording head

Abstract: PURPOSE:To provide the subject head wherein one wall surface of a pressure generating chamber is constituted by use of a vibratile magnetic plate, and the magnetic plate is vibrated by utilizing an electromagnetic force thereby to inject ink by a low- voltage driving operation. CONSTITUTION:A vibrating plate 5 made of a magnetic material is bonded to a main body 1, and further a coil core 9 containing therein a driving coil 8 is bonded to a vibrating plate 5. Between the core 9 and the vibrating plate 5, a gap of about 0.001-1mm, for example, is provided. In this state, a voltage is applied to the driving terminals 7a and 7b, and a current is caused to flow through the coil 8. Then, magnetism is generated in the core 9 to suck up vibration in the vibration plate 5 and to reduce the pressure within the pressure chamber 2 thereby to suck up ink by way of a feed path 3. Then, when the drive voltage is removed, magnetism is lost, and the vibrating plate 5 is restored to the original state by its own elasticity, the inner pressure being increased to inject the ink through the nozzle 4.

Method of controlling electromagnetic actuator in a camera, and actuator controllable thereby

Abstract: To control an electromagnetic actuator of the type having an armature movable in a magnetic field and means for urging the armature toward a rest position, a series of electrical pulses are applied to the actuator by a control circuit, the frequency of the pulses being above the cutoff frequency of the actuator, the position of the actuator being controlled by the duty cycle of the pulses. In a preferred embodiment, the actuator controls a shutter/aperture, the aperture size being determined by the duty cycle of the pulses, and the shutter time being controlled by the number of pulses applied to the actuator. An actuator controlled by the control circuit is of the type having a planar coil on an armature, mounted for movement in the plane of the coil in a magnetic field. To reduce friction and simplify construction, the armature is mounted on a flexure spring which urges the armature toward its initial position and also serves as a conductor to provide current to the armature.

Frequency response of interferometric fiber‐optic coil hydrophones

Abstract: The frequency response of optical fiber hydrophones is examined both theoretically and experimentally. Previous models have considered only either static pressures or high‐frequency (axially constrained) perturbations. In the present study, the acoustic sensitivities for fiber coils (5‐cm‐diam, 10‐m total length) are given for the range 100 Hz to 50 kHz. The observed frequency and coil orientation dependence of the pressure sensitivity is explained in terms of an approximate theoretical model. According to this model the acoustic driving force on the coil is the sum of two terms, a surface pressure and a pressure gradient term, of opposite sign. It is assumed that only the lowest‐order radial mode of vibration leads to a net optical phase shift in the coil. The observed peaks in the pressure sensitivity of the coils are found to be in the vicinity of the resonance frequency for the lowest‐orderadial mode.

Peripheral connector ring stator end winding for dynamoelectric machines

Abstract: The polyphase stator winding of a dynamoelectric machine consists of a plurality of coils circumscribed about one another. Each coil has at least one end turn which includes two coil sides and a C-shaped connector ring that joins the coil sides together. The coil sides are straight conductors, or ones that are slightly bent on each end, and are embedded within the stator slots and extend into the end basket region of the machine where they are joined together by the C-shaped connector rings.

Apparatus for maintaining a coiled electric conductor in a drill string

Abstract: Apparatus for downhole storage of an electrical conductor within a drill string in a borehole. The conductor is stored as a coil in a flexible storage means. The apparatus is desirably used to eliminate the short lengths of cable and the associated connectors which are normally added with each new section of drill pipe added to the drill string. Because the device is flexible, it may be used in deviated drilling.