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Showing papers on "Negative impedance converter published in 1979"


Journal ArticleDOI
TL;DR: In this article, a dc converter for the drive and control of a 45-kW traction motor in single quadrant operation with an efficiency of 96 percent is presented, which is due to the natural termination of thyristor currents, the positive confinement of the maximum momentary current and voltage stresses in the components below preset levels, and the low power dissipation in these components supported by a definite protection philosophy.
Abstract: A new type of dc converter for the drive and control of a 45-kW traction motor in single quadrant operation with an efficiency of 96 percent is presented. An improvement of the converter's reliability is due to the natural termination of thyristor currents, the positive confinement of the maximum momentary current and voltage stresses in the components below preset levels, and the low power dissipation in these components, supported by a definite protection philosophy. The high converter efficiency is attained at full power operation with an internal frequency of 10 kHz. The input impedance maintains its resistive character for all conditions of operation. The output port is characterized as a voltage-limited current source. Test data of an experimental model conclude the presentation of the converter's functional philosophy.

51 citations


Patent
30 Mar 1979
TL;DR: In this article, a switchgear assembly which includes a vacuum interrupter, a current transformer, and a capacitive voltage sensor is embedded within a cast epoxy housing mounted to a solidly grounded support structure.
Abstract: A switchgear assembly which includes a vacuum interrupter, a current transformer, and a capacitive voltage sensor, all embedded within a cast epoxy housing mounted to a solidly grounded support structure. The voltage sensor includes a first capacitor, which is formed by an interrupter conductor stud, a plate, and the cast epoxy disposed therebetween, and a second capacitor, which is connected between the plate and a metal tube extending outside the housing. The tube is connected to ground through a conductive coating, applied to the housing, having an impedance which is very low in comparison to the impedance of the first capacitor. The voltage signal on the plate, which is proportional to the stud voltage, is supplied through the center conductor of a coaxial lead to one input of a voltage level sensing circuit, where it is amplified, rectified, and compared with a reference voltage to produce a positive output signal whenever the stud voltage exceeds a first value, and thereafter produce a negative output signal whenever the stud voltage decreases to less than a second value lower than the first value. The conductive shield of the coaxial lead has a first end connected to the metal tube and a second end connected to the ground terminal of the voltage level sensing circuit and to ground through a ground path having a low impedance in comparison to the impedance of conductive coating ground path between the metal tube and the grounded support structure.

45 citations


Patent
26 Feb 1979
TL;DR: In this article, the Fourier transform of a window of the actual voltage and current over a time interval and of the modified current that would flow if the voltage on each side of the time interval was zero was calculated.
Abstract: An electrical power fault protection relay operates when the calculated impedance of the section of the system it protects shows a sudden change. The instantaneous voltage and current is measured. A calculation device then calculates the Fourier transform of a window of the actual voltage and current over a time interval and of the modified current that would flow if the voltage on each side of the time interval was zero. The actual impedance is calculated from the ratio of the Fourier transforms of the actual voltage and the modified current.

32 citations


Patent
26 Apr 1979
TL;DR: In this article, a precipitator system including a voltage controller and a conductive element coupled to the high voltage converter is described. And the controller is used to adjust the control signal when a spark is imminent, thereby avoiding it.
Abstract: There is provided a precipitator system including a voltage controller which produces from an alternating power source a variable output. This variable output drives a high voltage converter which applies a high voltage to a precipitator. This variable output is controlled by a control signal from a command subsystem. Preferably, the command subsystem is operative to repress the drive to the high voltage converter in response to its loading exceeding a predetermined limit during a corresponding limit interval. After this limit interval, the command subsystem is operative to rapidly restore productive drive to the high voltage converter, preferably by the next half cycle of the power source that has a polarity opposite to that existing at the beginning of the limit interval. In this fashion stablized operation is quickly achieved. Also included, preferably, is a conductive element that is coupled to the high voltage converter. This conductive element conducts in response to variations in the extent to which the high voltage converter is being driven. The command system may store successive values of the voltage across the conductive element, using such values to adjust the control signal according to a predetermined relationship. Such an arrangement can be used to adjust the control signal when a spark is imminent, thereby avoiding it.

31 citations


Patent
13 Mar 1979
TL;DR: In this paper, an electrically variable impedance circuit with a voltage-current converter and a current converter is presented, where the output current is proportional to the instantaneous input signal potential (v).
Abstract: An electrically variable impedance circuit in which a voltage-current converter circuit (3) is provided to produce a current (I') having a megnitude corresponding to an instantaneous input signal potential (v) applied to an input terminal (1) and a current variation of the vottage-current converter circuit is fed back to the input terminal (1), the current variation being controlled by a control signal (Vc) to vary the circuit impedance seen from the Input terminal (1). In order to expand the range of linesrity in impedance, the voltage-current converter is so arranged that the varying component of its output current is linsariy proportional to the inatan- taneous input signal potendial (v). and a current converter circuit (4) is provided which linearly converts the output current of the voltage-current converter circuit and whose output is coupled to the input terminal (1). The current converter circuit (4) is comprised of a PN junction (51) which develops a voltage which is the logarithm of the output current of the voltage-current converter (3) and a transistor (81) between the base and emitter of which is spplied the voltage developed by the PN junction (5 1 ) to produce a current which is the exponential of the voltage developed by the PN junction. (Fig. 1)

19 citations


Patent
Naaijer G J1
01 Mar 1979
TL;DR: In this paper, a d.c. converter synthesizes an alternating voltage by suitably and at the correct instants selectively combining a plurality of direct voltage sources into a variety of series connections.
Abstract: A d.c./a.c. converter synthesizes an alternating voltage by suitably and at the correct instants selectively combining a plurality of direct voltage sources into a variety of series connections by means of a plurality of semiconductor controlled switches and diodes. Polarity inversion is effected with a bridge circuit comprising switches. The converter load is connected to said bridge circuit. In this way it is possible to directly generate a 220 V, 50 Hz AC voltage without inductive elements, from solar panels, using accumulator batteries.

19 citations


Patent
Richard H. Baker1
22 Feb 1979
TL;DR: In this paper, a circuit for suppressing surge or transient currents between a DC power supply and a capacitive load includes a suppression impedance of relatively high impedance connected in series with the load between the DC supply and load, a transistorized control circuit for sensing the voltage across the load, and producing a firing signal when the level of voltage exceeds a predetermined level.
Abstract: A circuit for suppressing surge or transient currents between a DC power supply and a capacitive load includes a suppression impedance of relatively high impedance connected in series with the load between the DC supply and load, a transistorized control circuit for sensing the voltage across the load, and producing a firing signal when the level of voltage exceeds a predetermined level, and an SCR having its main current path connected in parallel with the suppression impedance, and its gate electrode receptive of the firing signal for turning on the SCR to by-pass the suppression impedance subsequent to application of power to the load.

18 citations


Patent
18 Jun 1979
TL;DR: In this paper, an improved instrument for use with an electrochemical cell that provides a system having enhanced stability and increased bandwidth is presented, which includes a voltage to current converter which drives the cell.
Abstract: An improved instrument for use with an electrochemical cell that provides a system having enhanced stability and increased bandwidth. The instrument includes a voltage to current converter which drives the cell. The current output of the voltage to current converter is linearly proportional to the differential voltage input. The voltage to current converter drives the cell in both the potentiostatic mode and in the galvanostatic mode of operation.

16 citations


Patent
23 Jan 1979
TL;DR: In this article, a combined current and voltage converter for metal-enclosed high-voltage installations with compressed-gas filling is described. Butteau et al. proposed a method to avoid any passages for the connecting leads through the housing.
Abstract: The invention relates to a combined current and voltage converter for metal-enclosed high-voltage installations with compressed-gas filling. In order to be able to avoid any passages for the connecting leads through the housing (1, 2), the electrode of the capacitive voltage converter part consists of an intermediate element (3) inserted into the housing in an insulated and gas pressure-tight manner. The intermediate element (3) has on its outside a layer of insulating material (9) and on top of this a metal layer (10). The whole (3, 9, 10) forms a support body for current converter cores (11) surrounded by secondary windings. The low-voltage capacity between the intermediate element (3) and the metal layer (10) is fed to an electronic measuring amplifier (14) via a screened measuring cable (12/12a). The current converter cores (11) are protected mechanically by a sheath tube (16), the latter simultaneously conducting housing currents. FIG. 1.

14 citations


Patent
30 Oct 1979
TL;DR: In this paper, a highvoltage crowbar circuit continually senses the load impedance and crowbars the output voltage applied to a load if the load's impedance falls below a selected value, and a differentiator circuit at the load senses variations in load voltage and can trigger the crowbar operation.
Abstract: A high-voltage crowbar circuit continually senses the load impedance and crowbars the output voltage applied to a load if the load impedance falls below a selected value. A differentiator circuit at the load senses variations in load voltage and can trigger the crowbar operation if the voltage variation as a function of time exceeds a preselected load.

13 citations


Journal ArticleDOI
TL;DR: In this article, an expression for the equivalent circuit of a waveguide tee junction coupled through a narrow transerse slot of variable length is determined from self-reaction and discontinuity in modal voltage.
Abstract: An expression for the equivalent circuit of a waveguide tee junction coupled through a narrow transerse slot of variable length is determined from self-reaction and discontinuity in modal voltage. Impedance loading on primary guide and coupling are deternined from the equivalent network parameter. A comparison between theoretical and experimental results is presented.

Patent
16 Jul 1979
TL;DR: In this paper, the input of an impedance converter is connected to the output of a complementarily connected transistor amplifier which performs linear operation within its essential operating range, to stabilize and decrease the output impedance of the amplifier on the average.
Abstract: In a crystal oscillator for solid state wristwatches, the input of an impedance converter is connected to the output of a complementarily connected transistor amplifier which performs linear operation within its essential operating range, to thereby stabilize and decrease the output impedance of the amplifier on the average. The impedance converter includes one or more active elements such as MOSFET's, junction type FET's and bipolar transistors. A quartz resonator is connected between the input of the complementarily connected transistor amplifier and the output of the impedance converter.

Patent
Adel A. A. Ahmed1
28 Mar 1979
TL;DR: In this article, a negative impedance network of the type which includes a current mirror amplifier having transistors in master and slave paths, a bias current is applied at the commonly connected control electrodes of the master and slaves path transistors, in inverse proportion to the voltage applied across the slave path.
Abstract: Within a negative impedance network of the type which includes a current mirror amplifier having transistors in master and slave paths, a bias current is applied at the commonly connected control electrodes of the master and slave path transistors in inverse proportion to the voltage applied across the slave path and thereby a negative impedance characteristic is derived through the slave path.

Patent
21 May 1979
TL;DR: In this paper, a voltage regulation-unbalanced voltage compensation control connected intermediate the supply and load of the polyphase system, the control including separately adjustable variable impedance elements provided by saturable core reactors for independently varying the voltage drops between the input and load terminals for each phase.
Abstract: Disclosed is a voltage regulation-unbalanced voltage compensation control connected intermediate the supply and load of the polyphase system, the control including separately adjustable variable impedance elements provided by saturable core reactors for independently varying the voltage drops between the supply and load terminals for each phase. The independent adjustment of the variable impedance elements is effected by a feedback control network varying the magnitude of current supplied to the DC control winding of each saturable core reactor in response to the existing load voltages across the load terminals.

Patent
22 May 1979
TL;DR: In this article, a process of pulse duration modulation for improved voltage and frequency efficiency of a multi-phase converter is presented. But the authors do not consider the auxiliary time dependent voltage of the output voltage of each converter phase.
Abstract: A process of pulse duration modulation for improved voltage and frequency efficiency of a multi-phase converter. The sum of the time dependent voltage of a load phase and of an auxiliary time dependent voltage is formed, wherein the auxiliary time dependent voltage is the same for all converter phases. The pulse duration of the output voltage of each converter phase is modulated with said voltage sum.

Patent
Adel A. A. Ahmed1
26 Mar 1979
TL;DR: In this article, a gain control circuit includes a first transistor with direct-coupled collector-to-base feedback converting current, applied to its collector, to logarithmically related voltage appearing between its emitter and base.
Abstract: A gain control circuit includes a first transistor with direct-coupled collector-to-base feedback converting current, applied to its collector, to logarithmically related voltage appearing between its emitter and base. This logarithmically related voltage is incremented or decremented by a voltage ΔV 1 proportional to T and applied to the emitter-base junction of a second transistor used as a logarithm of voltage to current converter, T being an absolute temperature close to that at which the first and second transistors are operated. ΔV 1 is developed as the potential drop across a resistive element R1, responsive to the output current of a current-to-logarithm-of-current converter circuit, making the conversion with a scaling factor proportional to T divided by the resistance R 1 of resistive element R1. Accordingly, the gain setting of the gain control circuit is unaffected by change in T.

Patent
28 Nov 1979
TL;DR: In this article, the authors simplify the circuit constitution by constituting the amplifier with a reference current source, operational amplifier, current to current converter and current to voltage converter, and this circuit can be used as the reference contact compensator.
Abstract: PURPOSE:To simplify the circuit constitution, by constituting the amplifier with a reference current source, operational amplifier, current to current converter and current to voltage converter. CONSTITUTION:When the reference current IB from the reference current source B and the current IIR from the external sensor are given to a current to current converter C via an operational amplifier A, the converter C outputs two currents IL and I which change correspondingly. This output I is the difference between the currents IIN and IB and fed to a current voltage converter D. The current I and IL change with corresponding value mutually, and when the current IIN is corresponded to the measuring temperature and the current IB is corresponded to the reference contact temperature, the output in response to the types of thermocouples used can be produced with the converter D, and this circuit can be used as the reference contact compensator.

Patent
29 Dec 1979
TL;DR: In this article, the authors proposed to eliminate the unnecessary peak current at an output transformer for the positive and negative polarities of the output voltage in the polyphase AC inverter by storing voltage information during a half cycle period of the poly phase AC in a memory, reading it and driving the output circuit of the inverter.
Abstract: PURPOSE:To eliminate the unnecessary peak current at an output transformer for the positive and negative polarities of the output voltage in the polyphase AC inverter by storing voltage information during a half cycle period of the polyphase AC in a memory, reading it and driving the output circuit of the inverter CONSTITUTION:The memory 1 storing the voltage information during half cycle period of the polyphase Ac is read by a counter 2, the information is applied to a D/A converter 3, the output from the converter 3 is applied to a comparator 8, which compares it with a signal from a triangular wave oscillator 9 to produce a pulse according to a pulse width modulation system, and the converter 3 is controlled in response to the output voltage and the set voltage by the control circuit 6 Subsequently, a switching circuit 12 is driven through a polarity discriminator 11 to produce an output Since the positive and negative half cycles are stored in the same address in the memory as common voltage information, the output voltage becomes symmetrical at both the positive and the negative, thereby preventing the drawback of flowing a peak current

Patent
12 Feb 1979
TL;DR: In this article, a sample and hold circuit for an automotive speed control system is presented, which includes a non-monotonic digital-to-analog converter suitable for fabrication as a highly dense monolithic circuit.
Abstract: A sample and hold circuit for an automotive speed control system is disclosed which includes a non-monotonic digital-to-analog converter suitable for fabrication as a highly dense monolithic circuit. The non-monotonic digital-to-analog converter precludes the occurrence of large positive errors in the analog output value, which might be caused by tolerance errors in the ratio of binary-weighted currents within the digital-to-analog converter, by including offsetting negative errors within the design of the digital-to-analog converter.

Patent
26 Sep 1979
TL;DR: An offset circuit for use in providing an offset signal to an analog-to-digital converter is described in this article, where the offset circuit is gated to provide a variable offset current directly to the integrator of the analog to digital converter, thereby eliminating adverse loading effects on the high input impedance.
Abstract: An offset circuit for use in providing an offset signal to an analog-to-digital converter. The analog-to-digital converter has an integrator for performing signal integrate operations and is connected to a digital display. The offset circuit is gated to provide a variable offset current directly to the integrator of the analog-to-digital converter, thereby eliminating adverse loading effects on the high input impedance of the analog-to-digital converter.

Patent
12 Jun 1979
TL;DR: In this paper, an automatic switching control circuit (ASCCC) is proposed to change the operating modes of a feedback-controlled system such as automatic frequency control circuit, and includes a first impedance element, an inverting amplifier and a second impedance element in a series circuit between an input terminal to which an error signal from the feedback controlled signal is applied and an output terminal from which a compensation signal is applying to a modulating element of the feedback control system.
Abstract: An automatic switching control circuit is responsive to a command signal as derived from manual tuning operation to change the operating modes of a feedback-controlled system such as automatic frequency control circuit, and includes a first impedance element, an inverting amplifier and a second impedance element in a series circuit between an input terminal to which an error signal from the feedback-controlled signal is applied and an output terminal from which a compensation signal is applied to a modulating element of the feedback-controlled system. A third impedance element is connected between the output terminal and a reference terminal. A switch is provided to establish a short circuit path between the input of the inverting amplifier and the output terminal. The voltage across the third impedance element automatically reduces to substantially zero voltage level in response to the presence of the short circuit path so that the feedback control is suspended. The voltage across the second impedance may be utilized to indicate the signal level of the error signal during the open and closed loop control modes.

Proceedings ArticleDOI
Thomas G. Wilson1
18 Jun 1979
TL;DR: In this paper, an analysis technique is presented which permits the designer to explore the start-up transient of a dc-to-dc converter when it is powered by a current-limited source.
Abstract: An analysis technique is presented which permits the designer to explore the start-up transient of a dc-to-dc converter when it is powered by a current-limited source. The current versus voltage characteristics of the source are superimposed upon those of the dc-to-dc converter. By noting the nature of the intersectition of these curves in the voltage-current plane, we are able to predict whether or not the converter is able to start up while powering a specified load.

Patent
12 Mar 1979
TL;DR: In this article, a method and apparatus for deriving radiofrequency impedance information of an electrical network, for example, an aerial, by using a current converter for inducing a radio-frequency current into the network and a voltage converter for impressing a radiofrequency voltage on the network, is presented.
Abstract: A method and apparatus for deriving radio-frequency impedance information of an electrical network, for example, an aerial, by using a current converter for inducing a radio-frequency current into the network and a voltage converter for impressing a radio-frequency voltage on the network. By applying radio-frequency signals to the converters, the resultant signals present in the network may be detected by connecting a radio receiver to the network, from which detected signals the impedance may be derived. By directly connecting the radio receiver to the network, the radio-frequency energy applied to the network by the converters may be kept very small.

Patent
18 Jan 1979

Patent
05 Jun 1979
TL;DR: In this paper, a charge/current converter for converting the charge output of the transducer into a current signal is presented. But the amplifier is intended for use in situations where a considerable distance separates the transducers from the control room.
Abstract: The amplifier is intended for use in situations where a considerable distance separates the instrument (for example a piezo-electric transducer) to be monitored and the control room. The amplifier comprises a charge/current converter for converting the charge output of the instrument into a current signal, the charge/current converter being connected to operate as a high impedance current source, a current/voltage converter and a connecting cable connecting the current output of the charge current converter to the input of the current/voltage converter.