Showing papers on "Electromagnetic coil published in 1978"

Variable stiffness guide wire

Abstract: A guide wire capable of being adjusted to provide variable stiffness for catheterizing arterial branches comprises an elongated helical wire coil with a plurality of core wires contained within and joined to the outer wire coil at their distal ends; at their proximal ends there is a handle having two elements which are movable relative to each other connected respectively to the inner core wires and to the wire coil to vary the extent to which the coil may be flexed, by tensioning the core wires and limiting the longitudinal expansion of the coil.

A Hot-Wire Liquid Water Device Having Fully Calculable Response Characteristics

Abstract: A liquid water sensor consisting of a thin copper wire wound on a hollow 1.5 mm diameter cylinder is described. Slave coils on either side of the master sensing coil reduce axial heat losses to an acceptable level, and allow for a simple relationship between power supplied to the wire and liquid water content. Wet wind-tunnel tests show that the system response to liquid water is easily calculable from a knowledge of the geometrical dimensions of the cylinder and the operating temperature of the hot wire. When operated at 100°C, the device has a sensitivity of 0.02 g m−3, a response time of better than 0.05 s and an accuracy of 5% at 1 g m−3.

The Accurate Computation of Self and Mutual Inductances of Circular Coils

Abstract: A new simple algorithm is presented for the calculation of the self and mutual inductance of coaxial circular coils, based on Bartky's transformation. The algorithm is applicable over the entire range of coil sizes, shapes and degrees of coupling. It is extremely efficient and produces results to a specified and arbitrary accuracy. The method may be extended to calculate the inductance of coils of finite thickness using two-dimensional quadrature formulae.

Linear synchronous motors

Abstract: PURPOSE:To obtain an excellent damping characteristic using a simple structure by setting up a damping means consisting of external impedance in which resistors and capacitors are arranged in series or in parallel between the input terminals of an armature coil.

Multiple frequency digital eddy current inspection system

Abstract: An apparatus for inspecting for cracks under installed fasteners and the like using a multiple frequency digital eddy current system. A computer with a plurality of digital arrays generate drive signals which are converted to analog and applied to the test coil, a second set of digital arrays generate balance signals, are adjusted in amplitude and phase and drive signals so that the output of the test coil is zero in a test specimen, output signals from a work piece are processed in the computer giving phase-sensitive crack detection.

Radio‐frequency plugging of a high density plasma

Abstract: Mirror end loss can be suppressed by applying an rf field at the mirror throat through low impedance coils. This method is verified to be effective for a high density plasma up to 1014 cm−3. Experimental results show that the rf field strength required for the plugging is dependent on the plasma density. The dependence differs according to the geometry of the coil. The mechanism of giving the density dependence is theoretically clarified for each coil. Particularly, it is shown that the electric field induced in the direction of the static magnetic field is intrinsic for the result of type‐III coil where its efficiency for rf plugging is insensitive to the plasma density.

Fast response electronic thermometer probe

Abstract: A probe having a temperature sensor mounted in its tip for measuring the temperature of a body into which the probe is inserted, has a heating coil positioned on the shank of the probe near the tip, and a second temperature sensor in the tip area positioned generally between the coil and the first sensor. A control circuit is operative to energize the heater coil in response to differences in the temperature sensed by the two sensors, so that the shank of the probe is heated to track the temperature rise of the tip of the probe upon insertion into a body whose temperature is to be measured. This heat servo thermally isolates the tip from the remainder of the probe, and eliminates long thermal time constants which would otherwise be associated with the flow of heat from the tip area down the probe shank. The time response of the system is then limited only by the tip area of the probe, which is made of high heat conductivity materials and is in intimate thermal contact with the body whose temperature is to be measured. Read-out of the sensed temperature is accomplished by circuitry connected to the tip sensor.

Radio-frequency plugging of a high density plasma

Abstract: Mirror end loss can be suppressed by applying an RF field at the mirror throat through low impedance coils. This method is verified to be effective for a high density plasma up to 10 to the 14th power/cu cm. Experimental results show that the RF field strength required for the plugging is differently dependent on the plasma density according to the type of coil. The mechanism of giving the density dependence is theoretically clarified for each coil. The electric field induced in the direction of the static magnetic field is shown to be intrinsic for the density independent result of type 3 coil.

Auditory prosthesis equipment

Abstract: An equipment is described using n electrode sets implanted in the cochlea at n different locations for allowing the brain to identify n different frequencies. A receiver implant is coupled to the electrode sets through a selector and an external emitter is coupled to a single receiver coil of the implant by means of a single emitter coil. In the emitter the sound information signal is processed for forming n analysis signals of which the frequencies correspond to said n different frequencies and raster signals which are transmitted by modulating a high frequency a.c. signal. Each raster signal comprises at least n pulses of which the durations correspond to the energies to be transmitted to the n electrodes.

Press fit electrical connection apparatus

Abstract: A pacemaker bipolar lead assembly, for being electrically connected to a pulse generator to transmit electrical pulses into a heart, that includes a pair of wire conductor spring coils electrically connected to conductor pins, the first coil being electrically connected to a tip electrode and the second coil being electrically connected to a ring electrode. An internal ring having an outwardly facing groove is press fitted within the ring electrode with the second coil extending through the groove to retain the second coil in electrical conducting relationship with the ring electrode. Electrical insulation is provided on the coils and the conductor pins except for one end portions of the pins, the part of the second coil that is in electrical contact with the ring electrode and the juncture of the first coil with the tip electrode. An insulated portion of the first coil extends through the internal ring.

Compensated pulsed alternator

Abstract: This invention relates to an electromechanical energy converter with inertial energy storage. The device, a single phase, two or multi-pole alternator with stationary field coils, and a rotating armature is provided. The rotor itself may be of laminated steel for slower pulses or for faster pulses should be nonmagnetic and electrically nonconductive in order to allow rapid penetration of the field as the armature coil rotates. The armature coil comprises a plurality of power generating conductors mounted on the rotor. The alternator may also include a stationary or counterrotating compensating coil to increase the output voltage thereof and to reduce the internal impedance of the alternator at the moment of peak outout. As the machine voltage rises sinusoidally, an external trigger switch is adapted to be closed at the appropriate time to create the desired output current from said alternator to an external load circuit, and as the output current passes through zero a self-commutating effect is provided to allow the switch to disconnect the generator from the external circuit.

Motorless magnetically coupled stirrer

Abstract: A plurality of magnetic field generating, electrical coils are preferably arranged in a circle, in one embodiment. Digitally controlled, recurring switching pulses are generated for sequentially defining a plurality of discrete time periods. During each of these time periods, a separate magnetic field is generated responsive to each switching pulse. The pulses are applied to the coil, in turn, for sequentially stepping a magnetic field in a rotary motion about the circle of coils. In other embodiments, the pole pieces may be arranged in another geometry. For example, they could be linearly positioned to slide a stirrer or to lift a stirrer member up a test tube. A substance which is to be stirred is placed in a non-magnetic container positioned within the stepping magnetic field. A stir rod of magnetic material is placed in the container and within the stepping magnetic field, so that the stir rod couples into and rotates or otherwise moves with the rotary magnetic field. The invention is particularly artractive when used with electronic controllers, such as counters, sequences, sensors, electronic controllers, or the like, since it is much easier for such a electronic devices to control digital pulses than to control analog currents.

Variable leakage transformer

Abstract: A variable leakage transformer or a variable voltage transformer comprising a magnetic core with a main-magnetic path and a sub-magnetic path, the main magnetic path having at least a common magnetic path with the submagnetic path, a primary winding wound on said common magnetic path of the core, a secondary winding wound on said main magnetic path of the core, means for controlling the magnetic flux in said sub-magnetic path, and said main-magnetic path having a thin air gap. By controlling the magnetic flux in the sub-magnetic path, the leakage of the flux induced by the primary winding from the main-magnetic path to the sub-magnetic path can be controlled. Thus the coupling between the primary and secondary windings, and conduction period in each cycle of the AC output voltage are controlled. The control of the conduction period in each cycle provides the control of the power transmitted from the primary winding to the secondary winding. Because of the presence of the air gap provided in the main-magnetic path, excellent control of the output voltage is obtained even when a load is small.

Coil less magnetic pickup for stringed instrument

Abstract: A magnetic pickup for an electronic amplification system of a stringed musical instrument wherein the variable electrical signal produced in response to the string traversing the lines of flux from a permanent magnet is generated by a Hall effect sensor, thereby eliminating the usual inductively coupled coil(s). The invention is disclosed in embodiments employing bar and horseshoe magnets with the sensor positioned on the opposite or on the same side of the magnet as the string. The sensor is an essentially planar device which may be positioned in a plane substantially normal to the lines of flux in contact with or spaced a predetermined distance from the associated magnet or positioned in a plane non-perpendicular to the lines of flux, or adjustably positioned with respect to the direction of flux lines to achieve the desired degree of sensitivity.

Δ-Connected, two-layer, three-phase winding for an electrical machine

Abstract: A winding for a Δ-connected, two-layer, three phase electrical machine with at least two shunt connected sets of coils per phase wherein the winding is arranged such that two adjacent sets of coils are connected with the coils of one set being cross connected and the other set being uncrossed. The coil end overhangs of the crossed set are longer than the overhangs of the uncrossed set. The voltage difference between adjacent conductor rods of one layer thus amounts, at all phase changes, at most to one winding voltage.

Inductor type synchronous motor driving system for minute control of the position and the rotation angle of the motor

Abstract: A system for driving an inductor type synchronous motor for minute control thereof which includes an inductor type synchronous motor having a circuit for driving m phases of driving windings and first magnetic teeth. A second group of magnetic teeth is provided facing the first group of magnetic teeth. Apparatus is provided for feeding electric current from a DC power source to the driving windings of the respective phases. The driving winding for one phase intersects the flux of a partial set of first magnetic teeth or at least two magnetic teeth to provide a flux-interlink. A group of solid state switches are interposed between the source for producing the electric current and the driving windings of the respective phases. A distribution pattern generator generates patterns in response to a command signal and controls the on-off states of the solid-state switches with the noted patterns to thereby form the electric current into trigonometric-functional-patterns. The minute control characterized with an electrical resolution number R, per electrical angle 2π (2π being one fundamental cycle) of the apparatus for feeding electric current, is equal to or larger than 3m per electrical cycle. The minute control is thereby determined to be stepless.

Thin film magnetic head assembly

Abstract: A thin film magnetic head assembly has a multi-turn electrical conducting coil, which is formed by deposition in an elliptical pattern. By virtue of the elliptical pattern, the coil turn portions between the back gap closure and transducing gap of the thin film head are relatively narrow, whereas the coil turn portions furthest from the transducing gap are widest. Corners and sharp ends are eliminated. Electrical resistance effects are thereby minimized and signal output is enhanced.

Electro mechanical position indicator using relatively moveable coils

Abstract: An electromechanical positioner indicator is provided which comprises first and second relatively movable parts, the first part including two oppositely facing surfaces which are everywhere equidistant and the second part including two surfaces which are everywhere equidistant and which are everywhere equispaced from and lie, closely adjacent to respective ones of the two surfaces of the first part. A first coil, preferably in printed circuit form, is secured to the first part and sensing coils, also preferably in printed circuit form, are secured to each of the two surfaces of the second part. The inductive coupling between the coils is dependent on the relative positions of the parts and thus the output of the sensing coils provides an indication of position. In one embodiment, the surfaces in question are formed by cylinders and in another, the first part is a disc and the main coil comprises an annulus. Particular coil and coil conductor shapes are also disclosed.

Composite type acoustic transducer

Abstract: A composite type acoustic transducer of a flat drive type electrodynamic transducer and a piezoelectric type transducer. A diaphragm has a membrane of any suitable shape made of high molecular piezoelectric material such as polyvinylidene fluoride, an electrode layer applied on one surface of a membrane, and a coil like conductor applied on the other surface of the membrane. A supporting member supports the diaphragm along its edge. A permanent magnet device produces a magentic field extending in parallel to a plane of the diaphragm and perpendicular to the coil like conductor. When an audio signal current passes through the coil like member and an audio signal voltage is applied across the electrode layer and the coil like conductor, the piezoelectric membrane shrinks and stretches, and at the same time a force to drive the membrane in a direction perpendicular to the diaphragm is generated due to an electromagnetic interaction between the current flowing through the coil-like conductor and the magnetic field.

Method of making armature of double insulation construction

Abstract: An armature of double insulation construction for commutator motors of the wound-rotor type and a method of making the armature. An insulator insulating an iron core from a shaft and windings from the iron core also insulates a commutator from the shaft and unites the shaft, iron core and commutator into an integral rigid body. The armature can be fabricated with high precision by a simplified method.

Process for preparation of film coils

Abstract: A process for the preparation of film coils is disclosed, which comprises forming a first plane coil layer by arranging a plurality of insulated spiral conductor patterns wound in the same direction adjacent to one another without any gaps, laminating on the first plane coil layer a second plane coil layer formed by arranging a similar plurality of spiral conductor patterns wound in the reverse direction, and connecting the conductor patterns in the first plane coil layer to the conductor patterns in the second plane coil alternately through windows in the insulation separating the plane coil layers to form one coil The flatness of the resulting structure allows plane coil layers to be laminated to form a stack The resulting coils may be employed to produce a multi-track recording head with minimal distance between the heads, transformers, and other inductors, including center-tapped inductors

Inductive device having orthogonal windings

Abstract: An inductive device comprising a magnetic core and windings for producing two or three substantially orthogonal magnetic fields at all points within the core The device may be utilized as an inductor or transformer in a variety of applications

Laminated winding for electric machines

Abstract: A laminated coil which may be used as a winding in electrical machinery is formed by multiple layers of thin electrically conductive material, each having an insulating layer on one side and being shaped in a specialized pattern. The patterns each form a winding and are shaped such that current flow therethrough generates a magnetic pole at only three of four cross-sectional sides. The laminated coil is formed of layers of these patterns arranged to provide a magnetic pole at all four sides.

MHD equilibrium in non-circular tokamaks with field-shaping coil systems

Abstract: This paper concerns the determination of axially-symmetric MHD equilibria with arbitrary cross-section. – A numerical solution to the appropriate 2-D free-boundary elliptic non-linear PDE has been used to relate current profile, coil configuration, and plasma geometry for non-circular tokamaks with external field-shaping coil systems. The bifurcation properties of the solution spaces for such tokamaks have been studied and the parameter regions wherein bifurcation occurs determined. The structural stability of the resulting equilibrium suggests ways of controlling the shape of different plasmas (in particular doublet plasmas) over a wide range of plasma parameters.

Stability of magnetic levitation

Abstract: The levitation forces on metal spheres in magnetic fields of axial symmetry are derived theoretically. Criteria for stability of the center of mass are obtained. It is shown for nonmagnetic samples that the desirable coil configurations are those which provide a constant field gradient along the symmetry axis. The formalism is applied to model coils of axial symmetry as an approximation to real spiral coils. An exact formula is derived for the axial component of the magnetic field on the axis of a spiral coil wound on the surface of a cone, and the transverse fields are evaluated approximately.

DC rotary machine

Abstract: An improvement in DC rotary machine is disclosed. The stationary field yoke of the DC rotary machine has a cylindrical field member and a cylindrical bearing member of a smaller diameter than that of the field member. These members are made of oil-containing sintered alloy as a unitary member. The inner cylindrical surface of the bearing part of the stationary field yoke supports a rotary shaft rotatably therein. A motor coil assembly in a shape of cup is fixedly mounted on the rotary shaft. A generator coil assembly is also formed in a shape of cup which has a central opening in the botton wall of the cup. The diameter of the central opening is approximately equal to the outer diameter of the bearing part of the stationary field yoke. The open end of the cup like generator coil assembly is disposed in opposition to the open end of the cup like motor coil assembly and these two open ends in opposition to each other are jointed together with the interposition of an insulating element therebetween so as to form a rotary coil unit which encloses the field part of the field yoke. A commutator for generator is formed in a shape of cylinder the inner diameter of which is larger than the outer diameter of the bearing member of the field yoke and the commutator is secured to the generator coil assembly keeping a spacing between the commutator and the bearing member.

30-MJ superconducting magnetic energy storage (SMES) unit for stabilizing an electric transmission system

Abstract: Electric power systems that have major loads and generation centers separated by large distances may experience low-frequency power oscillations. This type of oscillation has occurred on the Pacific ac intertie that connects southern California and the Pacific Northwest. A separate, almost parallel, dc-transmission line also connects these areas. The Bonneville Power Administration, which operates this transmission system, has overcome the instability by controlling the power transmitted on the dc-transmission line. A 30-MJ (8.4-kWh) superconducting magnetic energy storage unit with a 10-MW converter could also provide damping for this instability. The conceptual design of the 30-MJ coil and the cryogenic and electrical components of the system are described. The system is to operate at a maximum current of 5 kA and will modulate the ac Intertie at 0.35 Hz. Discharge will be controlled to retain a minimum stored energy of 20 MJ to limit cyclic strains in the coil and ac losses in the conductor. The conductor will be made of multistrand-copper and copper-matrix, multifilament NbTi superconducting wires on a stainless steel mandrel.