Showing papers on "Inductor published in 1972"

Current-Source Converter for AC Motor Drives

Abstract: The employment of current-source concepts in thyristor converters to obtain adjustable frequency and adjustable current waveforms is presented. The use of a dc filter choke and a current feedback loop to produce a regenerative current source is explained. The simplified inverter commutation circuit made possible by the current-source technique is also discussed. Finally, a brief review of the inherently rugged current-source converter's ability to provide wide range control of an ac induction motor is given.

Principles of electronic instrumentation

Abstract: Direct Current Circuits. Capacitors and Inductors. Alternating Current Circuits I. Alternating Current Circuits II. Diodes and Some Applications. Test Equipment and Measurement. Transducers. Transistors. Operational Amplifiers. Waveform Generators. Digital Basics. Digital Circuitry. Microprocessor Basics. Digital and Analog I/O. Noise.

Indicating and automatically resettable system for detection of fault current flow in a conductor

Abstract: Fault current flow in a conductor above a predetermined value generates a magnetic field in one direction between the poles of a magnetic core while current flow below this value generates a magnetic field in the opposite direction. A permanent magnetic indicator is movable in response to these magnetic fields and remains in a corresponding position until acted on by the next change in direction of the magnetic field. The magnetic core has one or more pairs of poles and the permanent magnet indicator has a corresponding polar arrangement. The magnetic core has sufficient retentivity to maintain the permanent magnet indicator in the position to which it was last operated when current flow in the conductor is interrupted.

Combustion engine driven generator including spring structure for oscillating the inductor at the mechanical resonant frequency between power strokes

Abstract: A generator in which the inductor is operatively connected to spring structure to be periodically oscillated relative to an induced current coil, at frequencies of mechanical resonance and responsive to irregular power strokes of an engine piston.

Metal base cookware induction heating apparatus having improved control circuit using infra-red temperature sensor

Abstract: A metal based cookware induction heating apparatus having an improved power supply and control circuit comprised of a chopper inverter including a gate controlled power thyristor coupled to and supplying an induction heating coil with periodic energization currents The gating circuit controlling operation of the chopper inverter is controlled by a temperature sensing arrangement that includes an infra-red heat sensor device arranged to view the metal-based cookware or other object whose temperature is to be controlled A constant current amplifier is connected in series circuit relationship with the infra-red heat sensor device across a source of low voltage direct current excitation potential and means are provided for periodically interrupting the view of the infra-red heat sensor device to produce an output alternating current signal component whose amplitude is indicative of the temperature of the metal-based cookware or other object being heated An alternating current amplifier including an adjustable temperature set resistor is coupled to the output from the infrared heat sensor device with the setting of the adjustable temperature set resistor serving to control the gain and establish the temperature level at which the output from the alternating current amplifier attains an operative level of magnitude An output on-off control amplifier either in the form of a Schmitt trigger type of circuit or reed relay is coupled to and controlled by the output from the alternating current amplifier for producing an amplified output on-off control signal representative of the temperature of the metal-based cookware or other object whose temperture is being controlled in accordance with the temperature setting of the adjustable temperature set resistor The on-off output from the temperature sensing arrangement control an inhibit circuit connected to and controlling a zero point sensing and control circuit that in turn controls the operation of a soft starting zero point switching device connected intermediate the rectified ac supply terminals and the thyristor switching device employed in the chopper inverter whereby both radio frequency interference effects and audible noise production by the inductive heating coil during energization periods from the chopper inverter is substantially reduced due to the fact that energization of the coil under the control of the temperature sensing arrangement is inhibited until only the beginning or near the beginning of each half cycle of the rectified full wave potential appearing at the output from the high voltage rectifier To further reduce RFI effects, a smoothing inductor having an inductance L3 and a smoothing capacitor having a capacitance C3 is connected in series circuit relationship across at least one of the commutating components of the chopper inverter power supply circuit The combined impedance of the commutating capacitor, the smoothing inductor L3 and the smoOthing capacitor C3 is capactive in nature and is series resonant with the communtating inductor L1 to establish the commutating period t1 The smoothing inductor and the capacitor serve to shape the output current flowing through the smoothing inductor which is used as the inductive heating coil to substantially a sinusoidal waveshape having little or no radio frequency interference emission effects Additionally, a capacitor switching arrangement is provided for the commutating capacitor C1 which is formed from a plurality of parallel connected capacitors and power rate controlling switching means for switching selected ones of the parallel connected capacitors into effective circuit relationship in the chopper inverter circuit in accordance with a desired rate of power production Where the improved induction heating apparatus is employed in connection with metal-based cookware, the inductive heating coil preferably is in the form of a helically-shaped planar inductive heating coil and is disposed under a heat transparent member such as an infra red transmissive pyroceramic that can form a smooth continuous tabletop over the induction heating unit and itself does not become heated except by conduction and convection from the metal-based cookware The inductive heating coil excites and heats the metal-based cookware directly so that all heat is generated only by the metal-based cookware and no excess waste heat is produced in the manner of known resistance heating units Since the temperature sensing units directly views the bottom of the metal-based cookware through the heat transparent member and controls the application of power to the induction heating coil, temperature control is directly related to the actual temperature of the pan or other object being heated by the induction heating apparatus As a consequence, a considerable improvement in efficiency and reduction of waste heat results Temperature control is accurate, rapid in response and there is no overshout in temperature such as is characteristic of temperature control systems which control the temperature of a heat source which is external to the object being heated Improved arrangements for the heat transparent member, infra-red heat detector, chopper device, and cooling fan together with preferred designs for the inductive heating coil with ferrite core of without to maximize coupling to the metal-base cookware or other object being heated, are described whereby further improvements in efficiency of operation, economy of components and minimum size are achieved

The theoretical output of a ring core fluxgate sensor

Abstract: This article proves that the output from a ring core sensor is directly proportional to the first time derivative of the product of dynamic permeability and magnetic intensity perturbation within the core caused by an external, uniform magnetic field. (Dynamic permeability is defined to be the slope of the hysteresis loop at a given point in time.) Assuming that ellipsoidal shells can approximate the core, the demagnetization factor can be "estimated" in the first order to be proportional to the first power of the quantity tape thickness (or number of wraps) divided by the core diameter. The constant of proportionality is determined from laboratory data. When an additional scale adjustment is applied to the resulting sensor output formula, the computed output tracks laboratory data for a range of sensor geometries.

Electrical inverter-rectifier circuit and inductor apparatus therefor

Abstract: The disclosed invention converts a square wave alternating voltage of relatively low voltage to a high direct voltage and is used as part of a conventional DC to DC voltage converter such as is found in electronic inverter/rectified regulated voltage power supply systems. An input transformer contains a primary winding and a plurality of separate secondary windings, such as four in one example. Each of the secondary windings is a single layer and all have the same number of turns. The secondary windings are electrically isolated and are wound one atop the other with their positive polarity ends facing the same direction in order to derive concurrently a plurality of equal AC voltages from the transformation of a voltage applied to the primary winding. The output of each of the secondary windings is rectified in a corresponding one of a plurality of rectifiers associated with the secondary windings into a plurality of equal DC voltages. These voltages are then added together in series or ''''summed'''' to provide the desired DC output power. A capacitor network which contains a plurality of capacitors, for example four, corresponding in number to the secondary windings, connected in series and the voltages from a corresponding rectifier is coupled in additive polarity across a corresponding one of the capacitors to provide the voltage ''''summing''''. In an improvement a plurality of inductors are employed with each one of said inductors placed in series with each corresponding ones of the output leads of each rectifier assembly so as to form with the capacitors an L-C circuit and thereby minimize the ripple voltage of the output power to the load. A novel multi-section inductor assembly having minimal distributed capacitance is utilized for said plurality of inductors and comprises a plurality of individual windings, divided into two groups each of which is insulated from one another, is of substantially equal number of turns, is of a single layer, is oriented with the windings in phase and wound upon a common nonsaturating magnetic core or lamination. Other than the first winding in one group and last winding in the second group the negative polarity ends of the winding in one group are connected electrically in common with the positive polarity ends of corresponding windings in the second group of windings.

Magnetic printed circuit

Abstract: A printed magnetic circuit board comprises a thin layer or sheet of magnetically permeable material (such as steel) laminated to an insulating baseboard which, after photo-etching, forms different desired magnetic circuit patterns. At least the exposed surface of the magnetic circuit is electroplated with copper or other material to prevent oxidation and to provide a degree of electrical shielding for the magnetic circuit. An electrical printed circuit is also available on the other side of the baseboard for use in forming electrical circuits cooperating with the magnetic printed circuits on the first side to result in a desired electromagnetic device. Specific printed magnetic circuit patterns are provided for use in a matrix of individually operable reed relays, a multiple pole reed relay, a relay or choke core and a transformer core.

Magnetic circuit for an electro-acoustic converter

Abstract: An improvement in an electro-acoustic converter having a magnetic circuit with an air gap therein, the improvement including an air gap formed of a magnetic material laminated with a conductive layer having a comparatively higher magnetic resistance in the magnetic circuit, thereby increasing a magnetic resistance against a magnetic flux caused by a voice coil and acting the conductive layer as shorting rings to decrease the inductance of the voice coil, and thus eliminating the reproduction distortion caused by the magnetic non-linearity of the magnetic circuit.

Analysis of Bulk Negative Differential Mobility Element in a Circuit Containing Reactive Elements

Abstract: The time and space evolution of the electric field in an inhomogeneous bulk negative differential mobility (NDM) element with a high n0l product, and the response of the surrounding lumped‐element circuit, is theoretically investigated. We consider a circuit in which an NDM element of low‐field resistance R0 and intrinsic capacitance C0 is in parallel with a parasitic capacitor Cp and in series with a load resistor, inductor L, and a battery. Exact numerical and approximate analytic solutions are obtained and discussed in terms of a damping parameter A [=(LC)1/2/R0C, where C=C0+Cp] and the ratio C0/C. Various oscillatory modes can all occur in the same NDM element for appropriate values of the circuit parameters. The dominant mode of circuit‐controlled oscillation in a series L‐parallel C circuit is the quenched multiple‐dipole relaxation mode. LSA relaxation oscillations occur only for a narrow range of circuit parameters and LSA sinusoidal oscillations are excluded because of domain domination, even for...

Basic circuit theory

Abstract: 1. Introduction. 2. Resistors, Sourses, and Simple Circuits. 3. Resistance Networks. 4. Capacitors and Inductors. 5. First-Order Circuits. 6. Second-Order aqnd Higher-Order Circuits. 7. Sinusoidal Steady-State Analysis-I. 8. Sinusoidal Steady-State Analysis-II. 9. The Laplace Transform-I. 10. The Laplace Transform-II. 11. Two-Port Network Parameters. 12. The Fourier Series. A. Matrices and Determinants. B. Complex Numbers. C. Use of Spice in Circuit Analysis. Answers to Review Questions. Answers to Selected Problems. Index.

Fail-safe monitoring apparatus

Abstract: An amplifier oscillates when a moving close-circuited inductor increases the coupling between a pair of input and output inductors. The oscillatory bursts, due to the periodic and proximate passage of the moving inductor, are integrated and averaged to provide a voltage level sufficient to maintain a warning circuit in a ''''safe operating'''' condition indication. The absence or open-circuiting of the moving inductor drops the voltage to a level such that the warning circuit provides an ''''abnormal operating'''' condition indication.

Impedance Measurements of Microwave Lumped Elements from 1 to 12 GHz

Abstract: The impedance measurement of small, microwave lumped elements of the order of 1 mm has been extended up to 12 GHz by a technique in which the frequency and Q of a resonant transmission line are perturbed by the connection of a lumped element. With the use of low-loss resonant coaxial lines, the technique has been applied to the measurement of lumped-element capacitors ranging from 0.4 to 3.6 pF and inductors ranging from 1.1 to 4.3 nH. Conductor Q values for capacitors as high as 1700 at 1.4 GHz and 100 at 12 GHz have been measured and estimates of dielectric Q values for capacitors of over 5000 have been obtained. Single-turn 1.1-nH inductor Q's of 40 at 1 GHz and 90 at 7 GHz have also been measured. The capacitors and single-turn inductors are found to have constant C and L values up to 12 GHz.

Dimmer circuit and gapped core inductor useful therewith

Abstract: In a dimmer circuit a summing amplifier combines a light intensity control voltage with a feedback voltage derived from the thyristor controlled ac power supplied to the lamp load. The summing amplifier output establishes the steepness of a ramp signal produced each ac half cycle by a ramp generator. A trigger circuit fires the thyristor device when the ramp signal reaches a certain level. In the feedback circuit a signal transformer coupled from the load is rectified, shaped by filter networks at the rectifier input and output, and used to charge a capacitor via an isolation amplifier. This capacitor provides a feedback voltage which, when summed with the control voltage, achieves a desired functional relationship between control voltage and light intensity, with compensation for load variation. A gapped core inductor is series connected with the ac supply to minimize certain adverse effects associated with turn-on of the thyristor device. Thus, use of the inductor reduces lamp filament vibration and minimizes inductive coupling to adjacent audio and other low level circuits. The inductor core includes both small and large air gaps to provide maximum inductance over a wide range of load current.

Parametric magnetic sensor

Abstract: A parametrically excited magnetic sensor, in which an inductance element is formed with a magnetic substance and a winding wound on the magnetic substance, in which a capacitor is connected in parallel to the winding to form a resonance circuit, in which an AC exciting current magnetic field is applied to the magnetic substance to generate a second harmonic oscillation wave having a frequency twice the frequency of the AC exciting current in the resonance circuit, so that a minute magnetic field is detected by utilizing a change in the phase of the second harmonic oscillation wave caused in accordance with the polarity of the minute magnetic field. The magnetic substance forms a part of magnetic circuit having a narrow gap so that the gap portion issued as a magnetic detecting head.

Single reactor force commutated chopper

Abstract: A force commutated thyristor chopper is disclosed in which a single commutation inductor is coupled in the free-wheeling path of the chopper together with a free-wheeling diode. The single inductor provides a chopper of relatively simple configuration in which main and commutator thyristors couple a commutation capacitor to opposite ends of the commutation inductor, and a charging diode is coupled in parallel with the commutator thyristor to facilitate charging of the commutation capacitor in opposite senses. The resulting circuit arrangement operates in a highly effective and efficient manner, minimizes trapped energy and protects the various component parts thereof by preventing dangerously high current and voltage transients.

Combined capacitor-inductor reactor device having transformer characteristics

Abstract: A combined capacitor-inductor reactor formed by spaced-apart layers of insulation and conductive foil rolled together around a core member to form a combined capacitor-inductor reactor. By connecting the input supply terminals to two different points on the same conductive foil and deriving the output from across a portion of the second foil which is coextensive with the part of the first coil intermediate the input terminals, the structure will exhibit capacitor connected transformer characteristics suitable for use as a fluorescent lamp starting and ballast circuit.

Power supply current detector system

Abstract: A power supply current detector system is provided which includes the filter choke inductor of the power supply, and which uses the winding resistance of the filter choke as a current sensor. The system of the invention produces an output which is indicative of the power supply output current, and which can be used for overload detection, and other purposes.

Induction heating coil arrangement in induction heating equipment

Abstract: Herein disclosed is an inverter device for use in an induction heating equipment in which an oscillating current having a suitable frequency is fed to an induction heating coil which is placed in proximity to a material to be heated, whereby eddy current and hysteresis loses are invited in the material to be heated so that heat is generated in the material. The inverter device features provision of noise preventive means, adapted to dampen out the high-frequency field built up by the component elements of the inverter circuit, leak current preventing means adapted to prevent leakage of current from the material to be heated to ground, and a variable inductor arrangement adapted to vary the apparent inductance of the induction heating coil. A typical application of the inverter device is an induction heating cooking equipment.

Voice frequency repeater

Abstract: A repeater useful in 2-wire line telephone systems employs a pair of hybrid sets, each of which is rotated 90 degrees relative to the normal operation position. A relatively small hybrid set having a relatively low inductance has an inductor connected in the secondary, which has an inductance related to the inductance of the primary, to eliminate the need for the retard coils typically employed in the direct current line for repeaters, and also the need for isolation transformers. Consequently, the repeater is relatively economical and smaller in size. An attenuator employing L half-sections in the input of each amplifier provides direct reading gain and a bandpass amplifier in the input of each amplifier provides increased stability by eliminating the high and low frequencies outside the voice frequency band.

Low reluctance inductor

Abstract: A closed magnetic circuit, high inductance device characterized by minimum reluctance and low cost of manufacture.

Apparatus including an oscillator for detecting short circuits in electrical components

Abstract: An apparatus for testing short circuit in electrical components such as motor or generator stators having plural windings with extremely low direct current resistance but measurable high frequency alternating current impedance. Preferably, the invention is embodied in a tester unit which includes leads for attachment to individual current windings forming a part of the article to be tested, and a transistor oscillator operated by a battery and having a display device such as a milliammeter in the output circuit in series with a diode or the like. A feedback circuit parallel with the milliammeter and the exterior load includes a center tapped inductor and a variable resistor in series with each other and controlling base current.

High frequency induction heating apparatus

Abstract: An apparatus for high frequency induction heating of elongated workpieces wherein the induction heating inductor is mounted as an integral part of the transformer secondary portion The transformer secondary is comprised of one or more spaced apart disc members having the inductor, which defines a desired workpiece heating pass, disposed therein and extending therebetween The transformer secondary portion is releasably retained between a pair of spaced apart transformer primary pancake coils with one of the coils positioned in a magnetic coupling relationship with each of the disc members The transformer secondary portion is easily removable from its magnetic coupling relationship with the transformer primary so as to permit selective use of other secondary portions which include inductors defining different sized workpiece passes

Computer-aided design and graphics applied to the study of inductor-energy-storage DC-to-DC electronic power converters

Abstract: The power handling portion of most regulated dc-to-dc electronic power conditioning circuits using a single self inductor for energy storage and transfer can usually be represented by one of three basic or canonical circuit forms. The circuit elements, consisting of an inductor, a transistor switch, a diode, and a filter capacitor may be arranged with appropriate topology to yield a voltage step-up converter, a current step-up converter, or a voltage step-up/current step-up converter. The design of a power converter requires making a number of decisions relating to the parameters of the circuit, including choice of semiconductor elements, filter capacitor, magnetic core material, magnetic path configuration and winding wire size. In the past, converter designs generally have required that several trial combinations of core size and permeability be tested by hand calculations. Experience and intuition were relied on to narrow the range of core size and permeability before starting the trial design computations. Recently, several computer-aided procedures have been described for use in the design . of the inductor for a single type of converter) This paper presents the results of the development of a series of nine programs which may be used to design the inductor in each of three basic converter forms in which the transistor switch is cont rolled by a regulator employing a constant frequency, constant on-time, or constant off-time pulse-width modulator. These nine programs, which contain the design algorithms and evaluation segments, are augmented by three additional programs which generate displays on a storage oscilloscope driven by the computer. These displays have proved to be extremely useful in evaluating the characteristics of the various converter-regulator combinations from an overall or global point of view.

Inductor simulation derived from an amplifier rolloff characteristic

Abstract: A technique for simulating inductance, based upon the single-pole rolloff of the voltage gain versus frequency characteristic of an amplifier, is presented. Analytical and experimental data are provided for a single-ended realization and a similar semifloating realization is discussed.

Nondestructive Eddy Current Testing

Abstract: When a coil is placed in proximity to a conductor, the magnetic field in the vicinity of the coil is altered by eddy currents in the conductor. The conductivity of a sample material may be determined by measuring the field. Closed-form solutions are presented for the magnetic field at the surface of a semi-infinite conductor for two cases: a semi-infinite coil, the end of which is in contact with the conductor, and a loop of wire on the surface of the conductor.

An implantable blood flowmeter using monolithic integrated circuits

Abstract: An implantable flowmeter has been developed for chronic radio-telemetry of blood flow in major arteries. Device consists of four unique monolithic circuits with a power drain of 13 mW from a 1.35-V supply.

Proximity switch including variable frequency oscillator with ferrite control element

Abstract: A proximity switch is provided having an oscillator with a resonant circuit with a variable inductance. The output of the oscillator is fed through a low pass filter and rectifier to a switching circuit which is activated at a predetermined amplitude. The proximity switch is activated when a control body of non-magnetizable ferrite material is moved in close proximity to the inductor of the resonant circuit, thereby increasing the inductance and reducing the frequency of oscillation, and maintaining or increasing the amplitude of the output of the oscillator, the lower frequency and high amplitude signal being passed by the low pass filter and applied after rectification to activate the switch. The switch is not activated by electrically conductive materials because the frequency of the oscillator does not change and the amplitude of its output is damped, and it is not actuated by magnetic materials such as steel chips or permanent magnets because of high eddy current and hysteresis losses induced into the resonant circuit and damping of its output which fail to provide the output necessary to trigger the switch.

Pulse control circuit for a dc load

Abstract: A circuit for providing controlled pulses of direct current to vary the speed of a direct current motor. A main controlled rectifier applies current to the motor. A commutation circuit consisting of an inductor, a capacitor and another controlled rectifier turns off the main controlled rectifier by reversing its polarity. Another circuit, referred to as a ''''ring-around'''' circuit, consisting of another inductor and controlled rectifier reverses the polarity of the commutating capacitor preparatory to the commutation of the main controlled rectifier.

Battery charging circuit for subscriber carrier equipment

Abstract: This charging circuit is a two-port network with an input port connected through a cable pair to a central office talking battery, and an output port connected across a local subscriber battery. The charging circuit comprises a current sensing resistor, a switching transistor, and an inductor connected in series with the talking battery and the local battery through the lines of the cable pair; a commutating diode connected across the series combination of the inductor and the local battery; a first control transistor for driving the switching transistor and having its base electrode regeneratively coupled to the collector electrode of the switch through the parallel combination of a diode and a capacitor; and, a second control transistor having its base-emitter junction connected across the resistor and having its collector electrode connected to the base electrode of the switch. The transistor switch alternately connects the inductor and the local battery to and disconnects them from the talking battery during charging of the local battery. When the switch is closed, the inductor stores energy while the local battery receives a charging current from the talking battery. When the switch is open, the magnetic field on the inductor collapses to provide a current through the commutating diode for charging the local battery. The second transistor compares the magnitude of the charging current that is drawn from the office battery and is sensed by the resistor with the reference voltage set by the base-emitter junction turn-on voltage of the second control transistor for driving the transistor switch out of saturation and controlling the operation of the latter in order to draw a relatively constant current from the talking battery.