Abstract: The technology for electrostatic enhancement of coalescence of water droplets in oil emulsions is critically reviewed. Historically, the electrostatic coalescer was invented for the petroleum-related industries in California [US Patent 987 115 (1911)]. Nowadays, this technology is generally considered for the separation of an aqueous phase dispersed in a dielectric oil phase with a significantly lower dielectric constant than that of the dispersed phase. Various designs have been introduced, with most using alternating current (AC) electric fields with mains frequency (50 or 60 Hz). The direct current (DC) electric field has been less common in the past as compared to the AC. In 1981, the concept of pulsed DC electric fields was introduced, together with insulated electrodes [Trans. IChemE 59 (1981) 229–237; UK Patent 217 1031A (1986)]. Since then, this has become more common in the electrocoalescence technology. Pulsed DC and AC fields are especially useful, when the aqueous phase content of the emulsion is high, to prevent short-circuiting between the pair of electrodes. Processing of oil from old wells is a good example, where the volumetric water content could vary significantly. Reported work by some workers indicates the existence of an optimum frequency, which depends on the electrode coating material, its thickness and the liquid emulsion composition. This is however, a contentious issue which has not been completely resolved. The characteristics and geometry of the electrode system (generally cylindrical or plate) influence the performance of the electrostatic coalescer, and are closely related to the type of the applied electric field and the emulsion used. There are basically two types of electrode: uninsulated electrode and insulated electrode. Combination of electrocoalescence and mechanical separation (e.g., centrifugal force) has also been introduced. Heating and the addition of chemicals have been shown to further enhance the electrocoalescence of water droplets. Other methods that can be combined with the electrical treatment are filtration, methods employing high pressure and temperature, and mixing. This review paper also looks at some of the current specific industrial applications using the electrocoalescence technology. Besides the oil and petroleum industries, this technology has potential applications in the edible oil industries such as palm oil, sunflower oil and vegetable oil processing. Most of the currently available equipment is very big and bulky, having a large inventory of emulsion. Therefore, we see the future trend for new developments to be in the direction of inventing small portable devices, incorporating features such as optimum electric fields and combined electrical and centrifugal forces to further enhance the separation of water-in-oil emulsions. Furthermore, a better understanding of the fundamentals of electrocoalescence will enable a better design of the geometry of the electrodes, of the flow field with respect to the electric fields, the type of dispersion used and the type of the applied electric field. © 2002 Elsevier Science B.V. All rights reserved.

Abstract: A modular apparatus for and method of alternating current photovoltaic power generation comprising via a photovoltaic module, generating power in the form of direct current; and converting direct current to alternating current and exporting power via one or more power conversion and transfer units attached to the module, each unit comprising a unitary housing extending a length or width of the module, which housing comprises: contact means for receiving direct current from the module; one or more direct current-to-alternating current inverters; an alternating current bus; and contact means for receiving alternating current from the one or more inverters.

Abstract: A LED driver (10) is disclosed. The LED driver (10) includes a high frequency inverter (20) and an impedance circuit (30). The high frequency inverter (20) operates to produce a high frequency voltage source whereby the impedance circuit (30) directs a flow of alternating current through a LED array (40) including one or more anti-parallel LED pairs, one or more anti-parallel LED strings, and/or one or more anti-parallel LED matrixes. A transistor (T3) can be employed to divert the flow of the alternating current from the LED array (40), or to vary the flow of the alternating current through LED array (40).

Abstract: The present invention takes the form of a current limiting apparatus and method for limiting current flow, induced when the level of an external signal is greater than an external signal threshold signal level, in a conductive loop formed by a medical device implanted within a living organism having electrically excitable tissue. The system includes an implantable pulse generator (IPG) system having a housing, a signal generator disposed in the housing that generates an electrical signal, and at least one lead extending from the housing to convey electrical signal to the patient. To limit the induced current flow, the IPG includes current limiting componentry, an impedance increasing element, and/or alternating current blocking elements. These components provide an alternating current impedance path to the electrical ground from a lead coupled to the capacitive element. Also disclosed are techniques for reducing the effective surface area of the current inducing loop caused by the IPG system.

Abstract: Between two direct current (DC) connections in a parallel wiring structure there is a intermediate power store and a bridge circuit with two parallel branches (A/B,C/D), to each of which are wired rectifier diodes (DA,DB,DC,DD) in parallel. Certain rectifier diodes (DE,DF) link to each other in single connecting paths (9,10) in an opposed conducting direction. Each of two alternating current (AC) connections links individually via a connection node to one of the parallel branches between two switch units by means of a connecting wire, in which each has inductive chokes (L1,L2).

Abstract: An implantable transcutaneous energy transfer device secondary coil module includes a housing, a secondary coil, power conditioning circuitry, and a low voltage, high power connector. The transcutaneous energy transfer secondary coil is disposed outside the housing and is configured to receive a time-varying magnetic field provided by a transcutaneous energy transfer primary coil, and to convert the time-varying magnetic field into a high voltage, alternating current electric signal within the coil. The power conditioning circuitry is mounted within the housing and is electrically coupled to the secondary coil. The power conditioning circuitry including electronics for converting the high voltage, alternating current electric signal from the secondary coil into a high power, low voltage direct current electric signal. The low voltage, high power connector electrically coupled to the power conditioning circuitry and extending outside the housing for connecting the secondary coil module to a power bus for delivering power to implanted devices.

Abstract: The invention discloses a power inverter using a microprocessor directly drawing the switching transistors and a circuit for computation of the actual power delivered to the load of a switching inverter. In addition, load variation power is achieved by adjusting the frequency or the pulse width of each half cycle and, in the case where a lamp or panel is involved, dimming. Also disclosed is that the microprocessor can be responsive to photometric input to adjust output as well as power line carrier information supplied on the input power to the device.

Abstract: The specification discloses an alternating current to direct current switching power supply, with power factor correction, and having an integrated rectifying bridge and boost circuit that results in the use of fewer power semiconductor devices in the rectification and boosting process. The use of fewer power semiconductor devices translates into a power supply with greater efficiency and/or smaller size. More particularly, the diodes in a rectifying bridge that typically conduct power back to the alternating current power source are paralleled by power MOSFETs, and the boost inductor is coupled between the source and the modified bridge. Charging of the boost inductor takes place through the power MOSFETs, resulting in only a two MOSFET power dissipation. Discharging of the boost inductor (and therefore supplying power not the load) takes place through two diodes, and therefore two forward power losses (as opposed to three diodes and three forward conduction losses associated in the related art). The reduction in internal power dissipation, therefore, results in smaller size and greater efficiency of the switching power supply.

Abstract: In a known method for regulating a delivery variable of a pump, which is driven by an electric motor operated with alternating current of variable frequency, especially via a converter, the input power of the motor is measured as the actual value for the delivery variable and is regulated by comparison with a desired value. To avoid the influence of the temperature of the motor on the delivery variable at constant input power, according to the invention upon a change in the temperature in the motor a corresponding compensating variable is taken into account in the control for the purposes of correcting the input power. As an alternative, associated values of the input power and the speed of the motor at a predetermined desired pressure value are determined empirically and stored as a table, and during operation a value of the input power belonging to a measured or approximately calculated speed of the motor is retrieved from the table as desired for regulating the input power.

Abstract: The invention concerns an installation for producing electric power comprising an electrical alternator (7) having a rotor preferably with permanent magnets integral with the rotating part (5, 6) of the wind machine, to constitute a rotary assembly (5, 6, 8) and a power electronics (12) module including means for converting (15) the alternating current produced by the alternator (7) into direct current. The method consists in adjusting the electrical characteristics of the electric current produced by the alternator (7) and the rotational speed of the rotary assembly (5, 6, 8) by modulating the direct current produced by the power electronics (12) module converting means (15). Preferably, the power electronics (12) comprises a pulse-width modulating rectifier (15), a rheostatic chopper (16) and a pulse-width modulating inverter (17) interconnected by a direct current bus (18). The inventive method and device enable to enhance the control of the wind machine in accordance with atmospheric conditions.

Abstract: A circuit for driving an organic light emitting element by alternating current in an active matrix organic light emitting display is provided A circuit of a pixel provided with a switching TFT and a current controlling TFT further is provided with an element that has a rectifying characteristic The switching TFT charges a capacitor in accordance with a data signal and the current controlling TFT controls light emission of an organic light emitting element in accordance with voltage supplied from the capacitor Reverse bias is readily applied to the organic light emitting element by applying voltage to the element that has a rectifying characteristic in the forward direction from an alternating current source

Abstract: We have observed an unusual reduction of shear stress with increasing shear rate under direct current electric fields, for an electrorheological fluid composed of sulfonated poly(styrene-co-divinylbenzene) particles dispersed in silicone oil. At all shear rates, the shear stress under the electric field is larger than that in the absence of the field, indicating that there is still some field-induced agglomeration of the particles. In contrast, the behavior under alternating current electric fields is the Bingham-fluid-type response commonly observed with electrorheological fluids. It is suggested that the conventional dipole–dipole interaction approach based on simplified microstructural models would be unable to explain these phenomena.

Abstract: A system for feeding direct current into an alternating current network includes a plurality of active inverters with each of the active inverters having an optimum input power and being connected at a respective input side to at least one direct current generator of fluctuating output power A switching device is included for the one or more direct current generators from a first active inverter to a second active inverter, or vice-versa, for effecting a switchover operation, with a control device initiating the switchover operation upon fulfillment of a condition; the control device including a device for determining when the condictionis fulfilled

Abstract: This paper reports a novel driving method for an annular plate-type ultrasonic motor. Instead of the direct current/alternating current (DC/AC) converter type driver using a conventional electromagnetic transformer, a compact disc-type piezoelectric transformer is used to obtain a high voltage output for driving the ultrasonic motor. The piezoelectric transformer is operated in the radial vibration mode at resonance frequency close to the resonance frequency of the ultrasonic motor. Later, it was found that the piezoelectric transformer could drive the ultrasonic motor, even if their resonance frequencies are not exactly the same by incorporating a matching network in the circuit. The maximum speed of the ultrasonic motor obtained by using this driving method is over 300 rpm. It is believed that the results of this study will have impact on the integration and miniaturization of the ultrasonic motor and its driving circuit.

Abstract: An electrical power cord for providing low-voltage alternating current outputs from a high-voltage alternating current source The cord includes an input terminal that is operable to receive power from a high-voltage alternating current power source The cord also includes first and second output terminals that are operable to output low-voltage alternating current The input terminal includes two distinct neutral wires

Abstract: A fuel gas compression system includes a system which operates on direct current, a system which operates on alternating current and a system which is capable of operating on either direct current or alternating current. In the system that operates on either direct current or alternating current, a jumper is provided which is placed in the circuit when an alternating current is provided. When a direct current is provided, the jumper is removed from the circuit.

Abstract: A distributed balanced photodetector with high saturation photocurrent and excellent linearity has been experimentally demonstrated. The maximum linear direct current (DC) photocurrent of 33 mA per branch is equivalent to 66 mA in single-ended photodetectors. A setup for investigating the alternating current (AC) linearity of the receiver is proposed and experimentally demonstrated. The receiver exhibits high AC linearity, even under high power operation. The bandwidth of the receiver remains unchanged when the effective do photocurrent is varied from 1 mA to 21 mA. The distribution of photocurrents was also measured. Device length for optimum radiofrequency performance is calculated and implemented in the design. A correlation between the dark current of the photodiodes and their failure mechanism has been established. Analyzing the failure mechanism, junction diodes are found to be more suitable for high power applications.

Abstract: Disclosed is a backlight system and a method for driving backlight capable of reducing noises and voltage fluctuations in power voltage due to a turn-on/turn-off of the lamp. The backlight system includes two lamps, a power supply unit for supplying alternating voltage or alternating current supplies power for driving the lamps to each lamp with a predetermined time lag or phase difference. With this feature of the present invention, the magnitude of noise and voltage fluctuations occurring in the power voltages supplied to the power supply unit may be significantly reduced. Thus, deterioration of display quality, flicker, etc., due to noise and voltage fluctuation can be prevented. Also, there is provided a backlight system which may produce a lamp driving signal with a constant frequency obtained by multiplying a frequency of vertical synchronization signal by an integer. With this feature of the present invention, a horizontal wave or a flicker can be easily eliminated by producing the lamp driving signal synchronized with the vertical synchronization signal and operation of the lamp can be stabilized as well because the lamp is driven by the lamp driving power with a constant frequency.

Abstract: A current inverter (12) generates an alternating current (AC). A resonance device (14) fed by the AC has a capacitor (Cs) and a transformer (16). Differentiated by opposed orientation, secondary units (SU) of first (20a) and second (20b) types are each formed from rectifier elements (Da,Db) and secondary windings (18a,18b) for the transformer. The first type SU supplies a first output voltage (Vb). The first and second SU types supply a second output voltage (Vab1). Independent claims are also included for a method for controlling a resonant converter and for a combinational circuit part.

Abstract: PROBLEM TO BE SOLVED: To attain size reduction for a machine as a whole and high workability at assembling by mounting an inverter control circuit on a flexible substrate and disposing it in a housing. SOLUTION: A power module 13 of an inverter device 11, the flexible substrate 19 equipped with the inverter control circuit 20, a current sensor 21, a power capacitor 22, and a radiator 23 are provided in a motor case 2 of the housing 1. These are accommodated in an inverter accommodating area 28 isolated from a power motor 8 by a shielding plate 27. The flexible substrate 19 is bent along the inner periphery surface 2A of the motor case 2. The power module 13 is controlled by the control circuit 20 to output an alternating current and to drive the power motor 8, thus disposing the inverter in the motor case 2 in a compact design with the inverter device 11 protected by the shielding plate 27. COPYRIGHT: (C)2004,JPO

Abstract: A method for measuring three-phases alternating current using a current sensor and an apparatus therefor, which are capable of not changing an average voltage for a switching period by changing reference voltages for modulating pulse width in a switching period of an inverter and compensating for the changed reference voltages in the same switching period It is possible to prevent current from being distorted, to detect three-phases output current in all of the switching periods, and to rapidly control instantaneous current by changing the reference voltages of arbitrary two phases in one switching period of an inverter, measuring current of each phase for the switching period using the current sensor, and compensating for the amounts of changes in the changed reference voltages of the two phase in the switching period

Abstract: A current mode output driver includes a pre-driver for pre-equalization. The current mode output driver drives a transmission line with an alternating current (AC) signal and a direct current (DC) signal. Characteristics of the transmission line are measured by comparing a received amplitude of the AC signal and a received amplitude of the DC signal. A ratio of the AC received amplitude to the DC received amplitude is compared to ratios derived from possible equalization settings to determine an equalization setting appropriate to equalize the channel.

Abstract: A method and apparatus for monitoring grounding of personnel and equipment in electrostatic discharge (ESD) sensitive areas. The device generates a low voltage alternating current control signal (60) which is applied to personnel (50) and equipment (350) being monitored. The device further includes signal conditioning (66) and detection means (70) to distinguish static charges from the control signal and transmit an alarm (72) upon detection of such static charge. The method encompasses the use of an alternating current control signal to detect static charge.

Abstract: A vehicle drive control apparatus including a motor, a battery, an inverter having a direct current supplied from the battery, wherein the inverter converts the direct current into an alternating current and supplies the alternating current to the motor and a controller that transmits a drive signal to the inverter so as to execute a weak field control, wherein a charging current supplied to the battery, at a time when execution of the weak field control is not allowed, is set to be smaller than an overcharging current indicating a maximum value of an electric current charged in the battery.

Abstract: The device of the present invention comprises a ring (1) of a ferrite material and two coils (4, 5) wound around it. A alternating current is fed to one of the coils (4). This current gives rise to an alternating magnetic field within and along the ring, which in turn generates an alternating electric field. A specimen (3) is placed in the alternating electric field. The dielectric properties of the specimen (3) affect the electric field, which in turn induces a magnetic field and generates currents in the coils (4, 5). As the dielectric properties of the specimen (3) depend on its glucose level, the glucose level can therefore be measured by determining a parameter depending on the inductances of the coils.

Abstract: A dynamic braking system for a vehicle, the system comprising an engine, an alternator, a plurality of alternating current (AC) electric traction motors, each coupled in driving relationship to a respective one of a plurality of driven wheels, a plurality of power inverters where each of the traction motors has excitation windings coupled in circuit with a corresponding one of the plurality of power inverters, a fuel-free dynamic braking controller, a fuel-free dynamic braking transfer switch located between one of the plurality of traction motors and the one of the plurality of power inverters in circuit with the corresponding one of the plurality of power inverters, wherein the one of the plurality of traction motors in circuit with the corresponding one of the plurality of power inverters that is separated by the fuel-free dynamic braking transfer switch does not generate and does not consume power, and wherein the fuel-free dynamic braking controller commands one of the plurality of power inverters that is separated by the fuel-free distributed braking transfer switch from one the traction motor to convert direct current (DC) power into AC power for use by the vehicle.

Abstract: The present invention relates generally to the reduction of odd harmonics of phase angle controlled loads. One embodiment relates to an apparatus for reducing odd harmonic currents introduced into an alternating current (AC) supply by a load (20) having a zero crossing detector (18) and a processor (14) coupled to the zero crossing detector. The zero crossing detector is coupled to the AC current supply for measuring voltage zero crossings of the AC current supply. The processor receives a user control signal (13) for controlling the load, such as, for example, a speed control, determines phase angles required at the voltage zero crossings of the AC current supply to implement the user control signal, and selectively modulating the phase angles when they are in a predetermined range of undesired phase angles in order to selectively reduce odd harmonics within the AC current supply.

Abstract: A high voltage power supply includes a current source that provides a continuous current signal, and a switching circuit that includes a plurality of switching elements. The switching circuit is responsive to the continuous current signal, and provides an alternating current signal. The power supply also includes a multiplier-rectifier circuit with at least one loading inductor, and having an input responsive to said alternating current signal to provide a rectified output signal. The switching circuit may be configured and arranged as an H-bridge circuit. The input of the multiplier-rectifier circuit is short circuited every half cycle of the alternating current signal during the transition from positive to negative current flow (or visa-versa).