Showing papers on "Electromagnetic coil published in 1970"

Torque limiting device

Abstract: 1,217,159 Positive clutches; controlling clutches COVENTRY GAUGE & TOOL CO Ltd 3 March, 1969 [5 Dec, 1967], No 55279/67 Headings F2C and F2L An overload release clutch comprises driving and driven rings 1 and 2 carrying dog teeth 21, 22 and drawn into engagement by a magnet or electromagnet 3 against a spring 6, the sides of the dog teeth being inclined so that when the transmitted torque exceeds a predetermined value the teeth cam over each other to move the members 1 and 2 axially apart until the air-gap 14 is too large for the magnet of electromagnet 3, and spring 6 disengages the clutch As shown, the ring 1 is fast with a rotating electromagnet 3, and ring 2 is fast with armature 4 Again, the ring 1 may be bearing mounted on a stationary magnet or coil To ring the predetermined overload torque, the coil 11 is in series with an adjustable resistance (12), Fig 3 (not shown) which may be set to determine the coil current and hence engaging force of the electromagnet A switch (10) is mounted parallel to the resistance to enable initial engagement of the clutch Closure of the switch by-passes the resistance and allows maximum current to flow in the coil to engage the clutch With the switch open, even when the resistance is at its minimum setting, the current is not large enough to engage the clutch across the air-gap 14

Optimum Geometry of Saddle Shaped Coils for Generating a Uniform Magnetic Field

Abstract: Saddle shaped coils for generating a field perpendicular to the axis of a cylindrical shell to which the coils are confined can be designed in a compact and easily constructed form. The central magnetic field of such a system and its second derivatives with respect to displacements from the center are given as functions of the coil dimensions, and conditions for minimizing these derivatives are discussed. A coil pair with a length‐to‐diameter ratio of 2 and circular arcs of 120° will have no second order central field derivatives in any direction.

Forces on Moving Magnets due to Eddy Currents

Abstract: A magnet or a current‐carrying coil, moving with constant velocity above a conducting plate, will experience magnetic lift and drag forces from the eddy currents induced in the plate. The lift and drag forces are calculated for various coil geometries on the assumption that the conducting plate is thin. For this model, the lift at high speeds approaches the force between the coil and its ``image'' located directly below it, and the drag force falls off as (velocity)−1. The ratio of lift to drag is found to be independent of coil geometry, but the velocity dependence of the lift is greatly affected by the geometry. The ratio of lift to coil weight can be as high as 2000 for a superconducting coil moving at 300 mph at 0.1 m above a conducting plate. The relevance of the calculation to magnetically supported high‐speed vehicles is discussed.

A molded coil

Abstract: A mold transformer consisting of a blank coil impregnated with an electrical insulating resin composition of epoxy resin or the like, said blank coil having as an insulator a highly impregnable non-woven polyester fabric or non-woven glass fabric interposed between a high-voltage winding and a low-voltage winding, between the high voltage winding and a magnetic core and between the lowvoltage winding and the magnetic core respectively, and a nonwoven polyester fabric between adjacent winding layers of each of the high-voltage and low-voltage windings; and a method of producing said mold transformer.

Alternating Current Distribution Between Planar Conductors

Abstract: The general theory for the vector potential produced by a sinusoidal current of finite cross section has been developed in a preceding paper.1 In the present work, this theory is applied to a coil between a number of plates of finite electrical conductivities and permeabilities. Linear, isotropic, and homogeneous media are assumed throughout. The Green's function solution is first obtained, and the principle of superposition is then used to effect the desired result. A number of physically observable phenomena, such as the impedance, the power loss due to the presence of the conductors, and the time‐averaged electromagnetic force on the conductors are subsequently calculated from the vector potential. The treatment is sufficiently general to allow the solution of a number of difficult electromagnetic induction problems, while each of the expressions obtained for the physically observable phenomena is in terms of an infinite integral that may readily be evaluated on a computer. In all cases for which exper...

Eddy current system for testing tubes for defects,eccentricity,and wall thickness

Abstract: Electrically conductive nonferromagnetic or electrically conductive ferromagnetic tubes are tested for wall thickness, eccentricity or defects by the eddy current test method using the transmission coefficient A coil system comprising an a-c excited primary coil means and an associated secondary (pickup) coil means is coupled sequentially to sections of the tube wall in such a manner that the tube wall section under test is disposed between the primary and the secondary coil means In one embodiment the primary coil produces a magnetic field whose lines of force are perpendicular to the tube axis, in another embodiment the primary flux is directed axially to the tube The flux transmitted through the tube wall is modified by the eddy current generated in the tube wall and the secondary coil means is inductively coupled to the flux emerging from the tube wall Responsive to relative motion between the tube and coil systems an electrical signal appears at the secondary coil means which is evaluated by electrical circuit means for the physical characteristics of the tube Various coil arrangements are disclosed to derive the stated parameters

Gearless drive method and means

Abstract: A synchronous motor has a circular rotating pair of cylindrical pole pieces of claw tooth form connected with propulsion means such as a propeller, and is driven by interaction of magnetic fields produced by segmented modular stator and field windings peripherally situated at spaced locations about the pole pieces energized by polyphase alternating current at a frequency determined by the speed of rotation of the pole pieces relative to the stationary stator and field coils. An additional DC signal is applied to the field windings. For higher power requirements, the number of segmented stator and field coil units can be increased.

Deformable pick up coil and cooperating magnet for measuring physical quantities, with means for rendering coil output independent of orientation

Abstract: A device is disclosed for the measurement of cross-sectional area, volume, and related quantities, as well as physical quantities which can be transformed into area, volume, and the like, and mathematical functions of such quantities. It comprises a deformable pick-up conductor disposed in a magnetic field, which field may be produced externally, or by passing current through the pick-up conductor itself. A voltage is induced in the pick-up which is a function of its configuration, and of changes in this. Means are disclosed for rendering the output of the device independent of the orientation of the pick-up, comprising variously the use of at least one auxiliary coil, linked to the pick-up, for producing a reference signal, the use of magnetic fields which are capable of change in orientation and may scan or track with the pick-up, and the use of a plurality of magnetic fields.

Compatible permanent magnet or reluctance brushless motors and controlled switch circuits

Abstract: Brushless motors have physical and electrical characteristics to be compatible with energization by the simple square or stepped wave voltages easily produced with inverter type motor control circuits having a small number of controlled switches responsive to a rotor position sensor. These motors employ a few pairs of opposing non-distributed stator windings arranged overlapping or non-overlapping with a predetermined winding pitch, and a constant gap magnetically polarized or non-polarized rotor with pole faces having related angular dimensions, to thereby produce rectilinear back emf voltages with approximately the same wave shape as the energizing voltages. The circuits can control the applied voltage to adjust motor speed.

Eddy-Current Losses in Rectifier Transformers

Abstract: Two methods are developed for evaluating the eddy- current losses occurring in a rectifier transformer during operation, i.e., when carrying pulsating currents. The first is based on the analysis of the whole waveshape; the second starts from the harmonic composition of current curves. Each system is useful from a different point of view, and both achieve the same results. Experimental measurements confirm the theoretical assumption, i.e., that eddy-current losses with pulsating currents can be some multiples higher than those evaluated by the tests prescribed by standards. Eddy-current loss evaluation is made for two-, six-, and twelve-pulse systems.

Metallic intrusion detector system

Abstract: A metal detection system comprising an electro-magnetic transmitter with a single transmitting coil and a receiver with a single receiving coil. The receiving coil is coupled to the radiated electromagnetic energy and the receiver generates a signal that may be used to indicate the intrusion into the electromagnetic field of a metallic object, to indicate whether such object is ferrous or non-ferrous, and to indicate the relative size of the metallic object.

Regulating power transformer with magnetic shunt

Abstract: A regulating power transformer consisting of a primary winding and a secondary winding positioned coaxial on the center leg of an E-type stack of magnetic lamination pack which is separated by a layer of I-type laminations having two coils wound thereon, the latter fitting into the windows of the E-type lamination. The Itype laminations provide the function of the magnetic shunt for the flux generated by the primary coil and serve as the magnetic coupling between the E-type laminations on the primary side of the transformer and identical E-type laminations on the secondary side of the transformer. Saturation of the shunt path to various degrees through control of the excitation of the coils mounted on the I-type laminations varies the amount of bypassed or shunted magnetic flux making it available at the secondary coil in a substantially linear proportion to the DC excitation. The transformer uses less iron, is faster in response than conventional regulating transformers and has an improved output wave form.

Wideband balanced current probe

Abstract: A wideband balanced current probe utilized for the detection and accurate measurement of very small currents flowing in a wire disposed in an environment involving extremely high electric and magnetic fields. My probe principally comprises a toroidal core having an electrically symmetrical bifilar wound coil disposed thereon and being protected from the high energy environment by a conductive, nonmagnetic shield. This probe provides a pair of symmetrical output signals which may be trimmed to provide even more precise electrical symmetry. The pair of symmetrical output signals is summed in phase and conveyed without contamination from the high energy field through properly balanced and shielded conductors to a relatively remote data recording unit.

Rotating electrical machine with means for preventing discharge from coil ends

Abstract: In order to prevent glow discharge from coil ends of a rotating electrical machine to adjacent grounded machine parts, the coil end is provided on the outside of its insulation with a conducting layer which is connected to ground by a voltage dependent impedance, such as a resistance, whose impedance decreases as the voltage increases.

Relay contact protecting circuits

Abstract: A contact protecting circuit for a relay having its operating coil energized from a DC supply and its contact controlling an AC load circuit. A triac connected in parallel with the contact conducts before the contact closes and after the contact opens to protect the contact from electrical arcing. In a first version, the triac is controlled by a secondary winding magnetically coupled to the relay coil. In a second version, the triac is controlled by a transformer connected in parallel with the relay coil. In this manner, the triac is gated only for a short time interval when triac conduction is needed and the triac will not continue to conduct in the event the relay contact fails to close.

Ion Cyclotron Wave Generation in the Model C Stellarator

Abstract: To permit quantitative comparisons between experiment and theory, ion cyclotron wave generation by the Stix coil system of the Model C stellarator is analyzed using a coil‐plasma model which closely approximates the physical system: filamentary currents at the coil loop positions induce plasma waves which propagate along the “cold” plasma column which is coaxial with a cylindrical waveguide. Most important in the analysis is the inclusion of finite electron inertia effects which cause the natural modes of the system to be characterized by two radial wavenumbers in place of one and which can seriously modify the properties of the ion cyclotron waves. Coil loading predictions are in good absolute agreement with experimental observations for wide ranges of plasma density and magnetic field, thus demonstrating the relevance of the cold theory to the laboratory plasma. However, magnetic field predictions are larger than the fields measured far from the Stix coil, suggesting wave attenuation by processes not contained in the theory.

Ground fault sensing circuit

Abstract: There is disclosed a ground fault sensing circuit usable with either AC or DC circuits. It includes a closed loop magnetic core having a gap. Two windings are disposed on the core in series, respectively, with the different conductors supplying the load. The windings are arranged in such a manner that, when the currents in the conductors are equal, there is no magnetic flux produced in the core and gap. Positioned in the gap is a solid state magnetic field sensitive element such as a Hall effect device or magnetic transistor. Underground fault conditions, a magnetic field appears across the gap and an output signal is generated by the solid state device. This signal is amplified and trips a circuit breaker in series with the load.

Multi-armature motors

Abstract: A direct current motor having at least two armatures arranged in parallel between parallel magnetic circuits established through the armatures independently exciting the armatures. In one embodiment a pair of iron core coils, positioned on respective opposing sides of a pair of armatures, provides the magnetic circuit. In another embodiment an iron core coil, interposed between two or more parallel armatures, forms the magnetic circuit. This common source of magnetic excitation forms parallel magnetic circuits wherein the motor has a dual operating characteristic in that the speed of one armature varies inversely with the speed of the other armature and vice versa until the higher speed armature reaches its critical rpm permitting the load to be increased without further change in the speed of either armature.

Automatic toner concentrate detector and control device

Abstract: Apparatus for monitoring and controlling the ratio of toner to carrier particles of a dry developer mix includes an inductive sensing coil positioned in contact with the developer mix. The voltage output of circuitry connected electrically to the sensing coil changes in response to a change in the inductive reactance of the sensing device due to changes in the ratio of toner to iron particles in the mix. A toner dispenser replenishes toner material to the mix in response to a predetermined change in the voltage output of the circuitry.

Natural performance extended range pick-up device

Abstract: A pick-up device for electrical guitars and like instruments includes pick-up coil formed by first and second windings wound in parallel on the same coil bobbin one on top of the other. The impedance of first, inner winding is less than that of the second winding, a turns ratio of one to four being typical, and the resultant output characteristic of the composite coil provides high quality reproduction of both treble and bass.

Two-piece winding bobbin for watt-hour meter potential coil

Abstract: A winding bobbin for a watt-hour potential coil is formed of two flanged spools that are fitted together to make a unitary bobbin assembly. The two-piece bobbin arrangement is characterized by incorporating an insulated chamber between the adjacent spools when they are in their assembled position, thereby to afford an insulated passageway for connecting the respective electromagnetic coils wound on the two spools in a manner such that the voltage gradient between successive end turns of wire on each coil is reduced to approximately 50 percent of the end-turn gradient that would exist on a single-coil bobbin having an equal number of turns on its supported coil.

Failsafe multiple transformer circuit configuration

Abstract: A failsafe multiple transformer circuit configuration, useful in providing power to electrical loads is disclosed. A circuit configuration for applying power to direct current loads includes a plurality of transformer circuits connected in parallel. Each transformer circuit includes a diode bridge rectifier circuit having the input terminals thereof connected across a secondary coil and the output terminals thereof mutually coupled in parallel with the output terminals of all other transformer circuits. Equalizing reactors are connected in series with the secondary coils to compensate for voltage imbalances that may be developed in the respective transformer circuits. A direct current load may be connected across the mutually coupled output terminals of the respective transformer circuits. Alternating current loads are accommodated by a plurality of parallel coupled transformer circuits each including a transformer having a pair of secondary coils. The respective secondary coils are parallel connected in two sets, one set for each half cycle. A diode rectifier is connected in series with each secondary coil and a silicon-controlled rectifier (SCR), associated with each set of secondary coils, is serially connected with an alternating current load. Equalizing reactors are employed in both sets of secondary coil circuits in the same manner as they were employed in the direct current configuration.

Method of making a magnetic transducer

Abstract: A planar magnetic transducer comprising a planar coil means, in the general shape of a spiral, with at least a portion of the coil means being sandwiched between the pole ends of two magnetic circuit plates. The method utilizes printed circuit techniques to batch-fabricate single end bifilar coil transducers which may be miniature in size.

Main field coil for railway traction motor

Abstract: A coil assembly having first and second outer windings and a third inner winding electrically connected in series. The outer windings have approximately one-half the number of turns of the inner winding. The outer windings are identically wound and each has an outwardly extending terminal. By turning one winding over during the assembly process both outwardly extending terminals will protrude from the coil assembly substantially midway between the upper and lower surfaces of the assembly.

Discharge-lamp operating device using thyristor oscillating circuit

Abstract: A discharge-lamp operating device is provided which comprises a power source connected in series with a discharge lamp and arc discharge stabilizing means of the linear inductor type, and a starting device including a capacitor connected in parallel with the discharge lamp and a series circuit including a voltage responsive switching element or a symmetrical switch element such as a bidirectional diode thyristor and a saturable non-linear inductor connected in parallel with the discharge lamp. Each filament of the discharge lamp is preferably interposed between the capacitor and the series circuit for improved preheating of the filaments. In addition, a bias coil which is magnetically coupled with the saturable nonlinear inductor can be connected in series with the capacitor to control oscillating frequency and voltage of the starting device. Further, there can be provided a second bias coil in series with the linear inductor so as to obtain desired effects according to the connections of the first and/or second bias coils which are magnetically coupled with the saturable nonlinear inductor.

Thin film coils and method and apparatus for making the same

Abstract: Thin film inductance coils, separately or in transformer combinations, are made by depositing on a substrate from vapor sources directed through selected apertured masks, superimposed layers of alternate films of electrically conductive metal and electrical insulating material in successive segments of each of a plurality of coil turns.

Polarity control system

Abstract: A system for controlling the transmission of electrical power between a D.C. power source and a load. The system includes a circuit having indicator lamps for visually indicating the polarity of the power source and of the load. Relays are utilized to prevent power transmission when the source and the load are improperly connected to the circuit. The circuit includes normally closed contacts of one relay in series with the coil thereof and a resistor in parallel with the normally closed contacts so that when the coil is energized, the voltage applied to the coil is automatically reduced during operation.

Heat exchange coil and housing therefor

Abstract: A heat exchange coil housing structure providing interchangeable side, top and bottom panels whereby the shifting of panels allows for airflow in a plurality of different directions without repositioning the heat exchange coil.

Breathing activity monitoring and alarm device

Abstract: An activity detecting means for detecting the movement of an animate object which includes a permanent magnet attached to the object. A pickup coil is provided around the area of movement of the object so that movements of the magnet induce a voltage in the coil. The output of the coil is delivered to circuit means which generates pulses when receiving the signal from the coil. An alarm means is operated by the pulses to provide an alarm signal which flashes off and on with each pulse received, but remains on when no pulse is received. Thus, the alarm means indicates the movement of the object by the flashing signal and indicates no movement by a continuous signal.