Showing papers on "Voltage published in 1984"

Instantaneous Reactive Power Compensators Comprising Switching Devices without Energy Storage Components

Abstract: The conventional reactive power in single-phase or three- phase circuits has been defined on the basis of the average value concept for sinusoidal voltage and current waveforms in steady states. The instantaneous reactive power in three-phase circuits is defined on the basis of the instantaneous value concept for arbitrary voltage and current waveforms, including transient states. A new instantaneous reactive power compensator comprising switching devices is proposed which requires practically no energy storage components.

The effect of high fields on MOS device and circuit performance

Abstract: A simple analytical model for the MOS device characteristics including the effect of high vertical and horizontal fields on channel carrier velocity is presented. Analytical expressions for the drain current, saturation drain voltage, and transconductance are developed. These expressions are used to examine the effect of scaling the channel length, the gate dielectric thickness, and the bias voltage on device characteristics. Experimental results from various geometry MOS devices are used to verify the trends predicted by the model. Using the physical understanding provided by the model, we examine the effect of device geometry scaling on circuit performance. We suggest that for gate capacitance-limited circuits one should reduce the channel length, and for parasitic capacitance-limited circuits one should reduce the gate dielectric thickness to improve circuit performance.

Electrosurgical generator with high-frequency pulse width modulated feedback power control

Abstract: A pulse width modulation technique regulates the output power of each cycle of a radio frequency surgical signal of an electrosurgical generator. The delivered power of the surgical signal is determined by multiplying the sensed current and the sensed voltage of the surgical signal. An error signal is established by the difference of the actual delivered power with respect to a selected desired output power. The error signal is operatively utilized to modulate the pulse width of each driving pulse which creates the cycles of the surgical signal. Limits on the sensed voltage and sensed current signals are established to limit the output characteristics of the surgical signal. A minimum current limit signal is utilized to limit the maximum output voltage into relatively high impedances. A minimum voltage limit signal is utilized to limit the maximum output current into relatively low impedances. Very rapid response times and very effective power regulation even into relatively high impedance tissues are possible with the pulse width modulation technique. The risks and problems associated with open circuit flashing, alternate path burns and closed circuit shorting are substantially reduced or eliminated.

Switch-induced error voltage on a switched capacitor

Abstract: A concise analytical expression for switch-induced error voltage on a switched capacitor is derived from the distributed MOSFET model. The result can be interpreted in terms of a simple lumped equivalent circuit. With this expression the dependence is investigated of the error voltage on process parameters and on switch turnoff rate, source resistance, and other circuit parameters. These results can be used to quickly predict the error voltage. The analytical expression is in close agreement with computer simulations and experiments.

Energy converter for implantable cardioverter

Abstract: An implantable medical device to deliver cardioverting energy to cardiac tissue in synchrony with detected ventricular depolarizations having a DC-DC flyback converter. The primary coil of the converter is periodically coupled and decoupled to ground by a timing circuit to effect charging of a high voltage output capacitor from a low voltage source through the secondary coil. A supply voltage detector alters the time period of the timing circuit to regulate the amount of current drawn by the primary coil. As the low voltage power supply depletes, its impedance increases tending to prolong the charging time of the output capacitor. Further regulating circuitry alters the one-shot time period to avoid loading down the supply voltage which could affect operation of other circuits. The preferred embodiment further includes a pacer, programmable memory and logic for controlling modes of operation of the pacer-cardioverter and parameters of the detection of arrhythmias and the pacing and cardioverting stimulus, and telemetry for telemetering out memory contents, heart signals and other data.

Instantaneous Feedback Controlled PWM Inverter with Adaptive Hysteresis

Abstract: A new control strategy for a PWM inverter controlled through adaptive hysteresis in an instantaneous feedback loop is theoretically analyzed and verified through simulations and a low-power experimental circuit. This control gives excellent performance under various load conditions, and it is especially effective in reducing load injected harmonics.

Switching electrical power supply utilizing miniature inductors integrally in a PCB

Abstract: Electrical switching power supply for microprocessors and the like comprising a high voltage d.c. source (30, 34, 32, 50) resonant circuit (38, 51, 42, 52) including a switching transistor (52) which is operated in Megahertz range and provides pulses, via a transformer (40), rectifier (56), smoothing choke (62) to a d.c. low voltage output terminal (66). The rate of switching is controlled by a pulse generator (54) which pulses variably in response to output voltage to thereby vary switching repetition rate and hold to a predetermined output voltage. The inductive elements use spirals (12A and 12A') of thin lines on the surface of a substrate board and ferrite plugs (20) passing through holes (22) in the board to provide miniature inductive elements built into the substrate for effective use in a microprocessor power supply, or the like, and in other applications. Power dissipating elements on the circuit are mounted to a common thermal ground (29) and the circuit as a whole, including such thermal ground is encapsulated to provide a plate form power supply.

Digital ac monitor

Abstract: An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

Lightning Induced Voltages on Power Lines: Theory

Abstract: Theory is presented which shows that nearby lightning return strokes can induce voltage surges of either positive or negative polarity on an overhead line depending on the location of the lightning relative to the line. The Telegraphers' Equations are solved with the return stroke vertical and horizontal electric fields as forcing functions. The hori zontal electric fields are calculated from measured or assumed vertical fields and assuned earth conductivities. For a typical return stroke, voltage waveforms are presented for a line of 500 m length and one of 5 km length for the following conditions: earth conductivities between 10-2 mhos/m and 10-5 mhos/m, earth permittivities between ??= 15 and ??= 3, and lightning ground strike points between 0.2 km and 5.0 km of the line at a variety of positions around the line. Measured voltages on a 460 m test line described in a companion paper are compared with calculated voltage waveforms derived from measured vertical electric fields, in accordance with the developed theory. Calculated waveshapes are found to be in moderately good agreement with the measurements, but calculated magnitudes are about a factor of 4 lower than measured. Possible errors in both theory and measurement are discussed. Voltage measurements reported by other investigators are, in general, consistent with the present theory

Battery control and fault detection method

Abstract: This is a method for control, fault detection, fault isolation, and state-of-health monitoring of batteries and battery arrays. The method consists of measuring all of the battery, cell, or cell group voltages, using statistics to determine a means voltage and a standard deviation voltage, then comparing all of the measured voltages to the mean voltage. If the measured voltage deviates from the mean voltage by an arbitrary amount (number of standard deviations) corrective action can be implemented or an alarm signal given. The measurements need to be made rapidly enough to eliminate battery or cell voltage changes due to state of charge or temperature changes and, in most cases, require a computerized data collection/reduction system. Absolute high and/or low voltage limits can be included to prevent catastrophic events. The concept can be expanded to include similar temperature, pressure and/or battery current measurements in an array.

Temperature sensor characteristics and measurement system design

Abstract: Describes the characteristics of three types of sensors currently in wide use: platinum resistance thermometers, thermistors and thermocouples. It then explains how the transfer characteristics of each sensor can be established using readily available temperature standards. The article then shows how these characteristics can be used to design signal conditioning circuits which convert the sensor output into a convenient voltage signal. Bridge circuits are necessary for the resistance thermometer and thermistor. It is possible to design a bridge with a nonlinear transfer characteristic which almost compensates for that of the thermistor. The design of an automatic reference junction circuit for a thermocouple is discussed. The article concludes by describing how a microcomputer can be incorporated into these systems as a signal processing element to improve accuracy. In the case of the thermocouple, the computer solves a quartic equation to arrive at an improved estimate of temperature.

Brushless DC motor controller

Abstract: The voltage supplied to the stator windings of a brushless DC motor is pulse-width-modulated by a circuit which interrupts the energization thereof for a predetermined period of time whenever the DC line current supplied thereto exceeds a current reference. The frequency and off/on duty cycle of the applied voltage is relatively high near zero speed to produce smooth motor starting torque and decreases with increasing motor speed. The pulse-width-modulation effects regenerative braking whenever the stator winding energization sequence is changed to reverse the direction of motor rotation.

Power conversion device for solar cell

Abstract: A power conversion device of simple configuration for a solar cell which permits the solar cell to be connected to the commercial power source and enables the maximum electric power corresponding to the amount of incident sunlight to be drawn from the solar cell. A power conversion device for a solar cell of this invention comprises a voltage controlled oscillator capable of generating oscillation with a frequency which is the function of the dc output voltage of said solar cell, an inverter controlled based on the output frequency of said voltage controlled oscillator to receive the dc output current of said solar cell and convert said dc output current into an alternating current, and an inductor serving to connect the ac output from said inverter to a commercial power source.

Tracing solution curves of non‐linear equations with sharp turning points

Abstract: Non-linear equations having multiple Solutions are usually associated with sharp turning points in the associated solution curves. Existing solution methods often fail or become extremely slow in the neighbourhood of such turning points. This paper presents an efficient algorithm based on the backward-differentiation formula (BDF) which overcomes this problem. For the special subclass of non-linear series-parallel circuits, this algorithm is generalized to allow all branches of driving-point and transfer characteristics to be traced efficiently. For any fixed value of the driving-point voltage or current source, this algorithm guarantees that all solutions are found.

Integrated circuit high voltage protection

Abstract: Protection of the thin gate oxide of MOS field effect transistors from irreversible puncture due to undesired high voltages and currents, generated by electrostatic discharge through handling or otherwise, is provided by a two stage circuit that operates to shunt thousands or tens of volts around the protected transistors. A first stage, employing a thick field effect transistor, protects against the very high voltage. A second stage, employing a thin field effect transistor, protects against lower but still excessive voltage. The protection circuit is formed as part of an integrated circuit chip by surrounding the lead bonding pad to which the protected transistors are connected.

Receiver apparatus for three-phase power line carrier communications

Abstract: A transceiver is provided with both voltage and current coupling to a three phase transmission line system. Each phase conductor is coupled to a common point which is connected in signal communication with an input to a receiver. Another input of the receiver is coupled to the neutral conductor of the power line system by an H-field coupler. A signal coupling unit is associated with the voltage couplers between the common connection point and the first receiver input. The receiver is provided with the capability of comparing the voltage signal with the current signal and selecting the stronger of the two. Therefore, the transceiver of the present invention is less adversely affected by standing wave problems since the voltage and current signals are out of phase and voltage nodes are associated with current antinodes and vice versa. Therefore, regardless of the location along the standing wave that the transceiver is located, the best signal available will be used for demodulation purposes.

Design of megawatt gyrotrons

Abstract: The design parameters of a 120 GHz gyromonotron capable of output powers in excess of 1 MW are determined. A nonlinear model of the interaction between the beam and rf field is used in which the efficiency is a function of only three normalized variables. By expressing the technological constraints in terms of these variables, permissible design parameters yielding high efficiency operation can be calculated. Constraints that are considered include ohmic heating of the walls, voltage depression of the beam, reduced coupling between the beam and rf field due to beam thickness, and efficiency degradation due to space charge forces within the beam. An analysis of the tradeoffs between current and voltage at the 1 MW level indicates that lower order modes can be utilized at lower voltages, but the constraints based on current limitations are difficult to satisfy. An 80 kV, 29 A design is presented that achieves a total efficiency of 44%. The primary uncertainty of these designs is the severity of competition due to parasitic modes. However, a number of isolated asymmetric modes appear capable of single mode emission at 1 MW based on present experimental results. Multimegawatt operation is also considered. It is shown that powersmore » exceeding 20 MW are possible if single mode operation can be achieved in very high order modes. The methodology presented in this paper is general and can be easily adapted to other frequencies and output powers.« less

Manufacture of high efficiency solar cells

Abstract: A Passivated Emitter Solar Cell (PESC) with reduced surface recombination due to reduced contact area between the top metal contact and the top surface of the cell, and having an open circuit voltage approaching 700 mV and an energy conversion efficiency in excess of 19% is disclosed The reduced contact area is obtained by a technique which simultaneously defines the lateral geometry of the top metal contact while allowing the top metal contact to be of much larger area than the area of contact to the top surface of the cell Also disclosed are methods of manufacture of solar cells having an increased open cell voltage obtained by improved passivation of the cell surface obtained by this technique

Improved offset-compensation schemes for switched-capacitor circuits

Abstract: Novel switched-capacitor stages which are free from the effects of op-amp DC offset voltage are described. The op-amps used in the stage need not slew between the desired output voltage and the offset voltage as in previously described offset-free circuits. The use of the new scheme in general applications is also discussed.

Pulsed power supply for an electrostatic precipitator

Abstract: A method and apparatus for generating a supply of pulsed power to an electrostatic precipitator where a residual collection field is maintained on the electrodes during interpulse periods while, in addition, high voltage pulses in excess of the residual are periodically impressed on the electrodes. The apparatus includes a series tuned circuit having a pulse forming section which creates a single damped cycle of oscillation to produce ionization current from a corona discharge electrode before unused power is returned to the pulse forming section. A blocking diode prevents the voltage on the precipitator from falling below the corona threshold voltage, and a series tuned trap circuit maintains the diode in conduction during pulsing to allow the return of unused energy.

Characterization of the pace-maker current kinetics in calf Purkinje fibres.

Abstract: Kinetics of the cardiac pace-maker current (if) were studied using high K+, low Na+ solutions under conditions where the current time course could be dissected from other components. Activation of if during relatively large negative pulses is S-shaped, and is approximated by an exponential function of time to the third power. Less-pronounced S-shaped activation occurs at potentials close to the middle of the activation curve (near -70/-80 mV). Here, allowing for the presence of a very slow component, the power required to fit the current activation approaches 1. The comparison between current activation and deactivation at the same potentials shows that although deactivation can be approximated by a single exponential, the two processes have a quite different time dependence, and this difference depends on the membrane potential. This behaviour is not compatible with Hodgkin-Huxley kinetics. While near the half-activation range the current decays with an apparently single exponential time course, at more positive potentials the current deactivation becomes sigmoidal. At least the third power of an exponential is required to fit its time course at potentials positive to about -40 mV. These data imply that both open and closed states correspond to several distinct channel configurations. The 'delay' in the current onset during a hyperpolarization is decreased by applying large, short hyperpolarizations before activation. Suitable pre-pulse durations and/or amplitudes can reduce the subsequent current activation to a single exponential. Records with and without a pre-pulse do not always superimpose. After the activation 'delay' has been removed by a suitable hyperpolarization preceding an activating pulse, the time course of its recovery can be studied by applying depolarizations of given amplitude and variable duration. The time course of the delay recovery does not seem to be linked to the time course of current deactivation recorded at the same voltage. Reduction of the activation 'delay' by conditioning pre-hyperpolarizations does not affect current decay during a subsequent depolarizing pulse. The current decay appears to depend only on the current amplitude reached before a deactivating pulse is applied. This, and the evidence in the preceding paragraph, suggest that the delay recovery and the current deactivation are independent processes. A reaction scheme is proposed, which has been developed on the basis of the experimentally determined kinetic properties of if. The channel model is composed of five gating subunits of three different types, not all independent in their movements.(ABSTRACT TRUNCATED AT 400 WORDS)

Portable arc voltage wirefeed welding system

Abstract: A portable wirefeed and control apparatus for use in consumable electrode arc welding systems which is capable of being powered by conventional AC or DC variable voltage or variable current supplies without modification of the power supply or the wirefeed and control apparatus. The portable wirefeed unit incorporates a wirefeed motor, a supply of weld wire, optional gas controls, and voltage regulating and protective control circuits all powered at welding arc voltage carried by the welding current supply conductor. The unit is circuit connected to the power supply by means of a single welding electrode supply conductor and a ground return. Electrode power, weld wire, optional shielding gas supply and welding gun control switch conductors are carried in a single flexible conduit extending between the control unit and a remote welding gun and wirefeed speed and thus wirefeed rate are partially responsive to variations in welding arc voltage.

Computation of Corona Space Charge, Electric Field, and V-I Characteristic Using Equipotential Charge Shells

Abstract: A charge simulation technique incorporating discretized equipotential charge shells in the volume is used to approximate the electric field and space charge around a single conductor in corona and to compute the voltage-current relationship for the discharge. No iteration is required in the solution method. Results are compared to corona in coaxial geometry, for which analytical treatment is also possible, and to experimental V-I measurements in line-to- plane geometry.

Control system for a voltage-type inverter

Abstract: In a control system for a voltage-type inverter which comprises a bridge connection of electric valves each comprising a reverse parallel connection of a semiconductor switching element and a diode, and converts a DC power to an AC power by means of PWM control, a voltage detection device is provided to detect an output voltage of the inverter. A voltage correction circuits corrects the pulse width of the pulse width modulation signal in accordance with the comparison of the detected voltage and the PWM signal. A drive circuit, which provides a dead time during which the switching elements of the electric valves connected in series with each other are concurrently non-conductive, uses the corrected PWM signal for driving the switching element.

Current Harmonics, Voltage Distortion, and Powers Associated with Electric Vehicle Battery Chargers Distributed on the Residential Power System

Abstract: The harmonic performance of the networks of several types of electric vehicle (EV) battery chargers is documented. Cumulative effects at the substation level for random distributions of each of five different charger types are reported. Chargers with and without current- smoothing inductors and with and without controlled rectifiers for maintenance of constant current are included. Results are reported as magnitudes of expected harmonic current; active power; apparent, reactive, and distortive volt amperes; and power factor hour by hour over typical daily recharge cycles for the network of chargers. Results regarding comparisons among chargers demonstrate the desirability of including a current-smoothing inductor in the charging circuit and indicate that constant-current type chargers using controlled rectifiers generate significantly more harmonic current than the simple noncontrolled taper-current chargers. Typical third harmonic current values of 15 A per charger on the 120-V side and 20 A per phase on the 12.8-kV side for a network of chargers (at ten percent penetration of chargers into the residential distribution network) indicate the possibility for harmful effects to customer and utility equipment and for interference into communications circuits. The results reported here should be useful in both predicting harmful effects at various densities of EV chargers on the residential network and in designing chargers to minimize those effects. supported in part by the New England Electric System.

Electric Distribution Protection Problems Associated with the Interconnection of small, disperesed Generation Devices

Abstract: This paper discusses the results of simulating three potential protection problems associated with the interconnection of rotating-type, small dispersed storage and generation (DSG) devices to the electric distribution system. These simulations were performed as part of a study to address the-adequacy of the electric utility industry's present protection practices and hardware for distribution systems with DSG. The simulations considered phenomena such as the effect of dispersed generati, on infeed on the coordination of fuses, resonance of an isolated section of feeder with a three-phase DSG device, and the islanding of a DSG device on an isolated feeder. The phenomena were simulated for a 12. 47 kV feeder with DSG. A digital computer program was used to calculate the transient currents and voltages produced on the feeder for the three types of phehomena. Results of the simulations indicate that these are concerns which should be considered by electric utilities in the connection of dispersed generation sources to the electric distribution system.

Power supply with noise immune current sensing

Abstract: A power supply (20) incorporates a switching regulator circuit and a flyback transformer (26) having diodes (42) for unidirectional current flow from an output circuit of the transformer to a load (24). Substantially noise-free sensing of currents in both input (32) and output (34) windings of the transformer is provided by a sensing circuit composed of a sense winding (46) on the transformer and an integrator (50) coupled to the sense winding. The integrator provides an output signal proportional to volt seconds or flux which, in turn, is proportional to either the input current or the output current. The input current and the output current flow alternately due to a switching action of the regulator circuitry. The regulator circuitry includes an electronic switch (38) coupled via a comparator to an output terminal of the integrator so as to initiate a pulse of current in the input winding when the output currents drop below a preset value, and to terminate the input current when the input current exceeds a preset value. A bank of capacitors (54) connected to the input winding (32) stores electric energy in the intervals between pulses for subsequent discharge into the transformer during the current pulses. The foregoing arrangement of the power supply circuitry provides for isolation of input and output sections of the power supply to prevent the coupling of noise. An overvoltage sensing circuit may also be coupled to the output winding (34) for acting via a logic unit to terminate input current during intervals of excessively high output voltage.

Voltage regulator for charging generator

Abstract: A voltage regulator for a charging generator is disclosed which comprises an a.c. generator having armature windings and a field winding, and a battery which receives the rectified output of the a.c. generator and is charged by the same. The voltage regulator regulates the output voltage of the a.c. generator by controlling the current flowing through the field winding. To prevent the output voltage of the a.c. generator from becoming a high voltage when a connecting wire connecting the rectified output of the a.c. generator to the battery is broken, the regulator also includes an abnormality detection means which compares the rectified output of the a.c. generator with the battery voltage and detects the abnormality when both voltages are different by more than a predetermined value. This arrangement makes it possible to detect the abnormality at the point of time where the output voltage of the a.c. generator is not yet very high.