Showing papers on "Converters published in 1984"

A Comparative Investigation of a Three-Phase Induction Machine Drive with a Component Minimized Voltage-Fed Inverter under Different Control Options

Abstract: Possibilities for minimizing component cost in variable- speed drives with frequency control by solid-state converter are investigated. It is shown that in a three-phase system voltage and frequency control of a three-phase squirrel-cage machine may be attained by PWM of the output of a simplified bridge inverter with only four switches. As the phase voltages are in principle asymmetrical, this technique is called phase asymmetric PWM (PAPWM). The operational region of PAPWM control is investigated theoretically in the frequency plane, compared to PWM control of a six-element bridge, and shown to have application possibilities. The system was experimentally tested on a 1O-kVA four-transistor inverter and experimentally compared to the operation of a six-transistor inverter of the same rating. The entire signal electronics subsystem was also minimized regarding components by using a specially dedicated IC circuit developed for PWM applications in three-phase systems. These results prove that a PAPWM system with a B4 bridge can be operated to give the same operational drive characteristics as a B6 bridge with PWM. The price to be paid for using a bridge with only four switches lies in the higher pulse frequencies required to give the PAPWM the same characteristics as a conventional system. Since transistor switches may be operated at high switching frequencies with low switching losses, the system is well suited to transistor inverter control of induction machine drives.

Resonant Switches - A Unified Approach to Improve Performances of Switching Converters

Abstract: In searching for a general "zero-current-Switching" technique for DC-DC converters, the concept of resonant switches is developed. As a combination of switching device and LC network, the resonant switch offers advantages of quasi-sinusoidal current waveforms, zero switching stresses, zero switching losses, self-commutation, and reduced EMI. Furthermore, application of the resonant switch concept to conventional converters leads to the discovery of a host of new converter circuits.

Wide-band electrooptic guided-wave analog-to-digital converters

Abstract: Progress in the development of high-speed electrooptic A/D converters is reviewed. A/D converters of this type have been operated at 1 gigasample/second (GS/s) in 2- and 4-bit structures for 500-MHz analog bandwidth. The converter consists of an array of LiNbO 3 guided-wave interferometric modulators that function as an analog amplitude analyzer, pulsed lasers for optical sampling, and high-speed monolithic comparators/demultiplexers to generate the digital levels and slow the data to ECL-compatible rates. The operational principles of the converter are summarized and a performance analysis presented. The analysis indicates that with currently attainable components, conversion in the 4- to 6-bit range at rates from 1 to 3 GS/s is feasible. Experimental results for several converters are summarized, including a description of beatfrequency tests for analog signals with frequency content up to 500 MHz that indicate the analog bandwidth capabilities of this device. The electrooptical technology is compared to competing high-speed A/D technologies in Si, GaAs, and superconducting materials and the relative merits analyzed. It is found that the electrooptic approach eliminates some of the fundamental and severe problems of conventional converters (e.g., sampling pickup and large numbers of comparators). Finally, application of this converter to wide-band signal-processing problems is described. It is noted that there are numerous applications where a moderate number of bits at a high (gigahertz) sampling rate is attractive.

Analysis of Resonant Converters

Abstract: The load parameter, Q, and the ratio of the switching frequency to the resonant frequency, Fs/Fo, characterize the operation of resonant converters. An accurate do analysis of the series and parallel resonant converters is given in terms of these parameters whereby the conversion ratio, peak stresses, and diode conduction time are determined. An exact and systematic method of small-signal analysis is given whereby the control-to-output transfer function, audio susceptibility, and input impedance are determined at a given operating point. In addition, simple and approximate transfer functions are obtained under high-Q assumption.

The generalized use of integrated magnetics and zero-ripple techniques in switchmode power converters

Abstract: Methods are presented that allow the discrete transformers and inductors of switchmode power converters to be unified in single magnetic structures It is demonstrated that unified magnetics and zero ripple operation are general phenomena applicable to all types of switchmode power converters

Design and Performance of a Converter Optimized AC Machine

Abstract: The design and performance of a unique concentrated winding machine specifically designed for operation with a static power converter is described. When operating in tonjunction with a converter supply, the machine is theoretically capable of 15 percent more power output for the same active copper and iron than a conventionally designed synchronous machine of the same rating. The performance of the machine operating as a generator feeding a rectifier load is described, the theoretical predictions are compared with test. The potential of such a machine operating as a motor is also described.

Coordinated Active and Reactive Power Modulation of Multiterminal HVDC Systems

Abstract: Coordinated active and reactive power modulation is evaluated for centralized and decentralized DC power modulation. Linear analysis and simulation studies are made for different DC network configurations. Simulation studies made on a hybrid computer demonstrate that coordinated reactive power modulation not only improves the system damping but it also alleviates the mode shifting problem during the modulation.

New Integrated-Magnetic Power Converter Circuits for Telecommunication Systems

Abstract: Novel integrated-magnetic alternatives to conventional DC-to-DC power converter circuits are discussed together with principles behind the integration process, typical electrical waveforms observed within such topologies, and ideal voltage transfer functions that can be achieved Guidelines in the modeling, analysis, and practical design of these unique converters are also given

Converter engineering: An introduction to operation and theory

Abstract: Supply-Commutating Converters. Converters with Turn-Off Valve Arms. Converters on the Three-Phase System. Symbols. Bibliography. Index.

Controlled rectifier element, which is connected to an inductor, and its use

Abstract: A field-effect transistor (F1) which is operated in the reverse direction is used for a controlled rectifier element which is connected to an inductor (W). The field-effect transistor (F1) is controlled via a current transformer (U) such that current can flow only during the demagnetisation of the inductor (W). This arrangement is suitable especially for low-power voltage converters having a pulsed current with gaps.

Analog/digital converter

Abstract: PURPOSE:To improve the A/D conversion processing efficiency by transmitting simultaneously the conversion start signals to all of plural A/D converters to start conversion processing and applying an interruption to a CPU when the conversion end signals are all given from those A/D converters. CONSTITUTION:A CPU1 gives conversion start signals ADST at a time point t0 to A/D converters 2a-2c which convert analog signals a-c into digital signals. Thus these converters start the conversion processing respectively. The conversion end signals EOCo-COCc are delivered from converters 2a-2c and supplied to an AND gate 3. These end signals are supplied to the CPU1 as interruption sgnals, and each conversion data is read into the CPU1.

Application of the thin film permalloy magnetoresistive sensors in electrical measurements

Abstract: Thin film magnetoresistive magnetic field sensor may be used in the design of measurement converters. Two basic function modules - a multiplier and a direct current transformer - have been described. Using the modules following converters have been constructed and investigated: one- and threephase power converter, watt-hour meter, direct current transformer, adder and contactless current converter. Main advantages of these converters are: design simplicity, small geometric dimensions and relatively low errors - of the order of 0.5%.

An automatic error cancellation technique for higher accuracy A/D converters

Abstract: An automatic error cancellation technique for higher accuracy successive-approximation analog/digital (A/D) converters is described. The technique uses a binary-weighted capacitor array as its own reference, and no other special elements are required for capacitor mismatch compensation. Experimental results indicate that more than 14-bit A/D conversion can be performed on a conventional MOS IC chip without trimming.

Digitally controlled rectifying system for driving a motor

Abstract: A digitally controlled rectifying system used for driving a d.c. motor through antiparallel connected forward and reverse converters. The firing phase angle of the converters is shifted by 180° at a time of gate switching operation for the converters so that the load current is formed to become zero, and after the gate switching operation the firing phase angle is shifted to a position at which the load current is substantially zero, whereby the time lag of control occurring at the switch­ ing operation of the converters can be minimized irrespective of the load condition.

The use of microprocessors for control and fault detection of electronic power converters. contribution to safety and maintainability

Abstract: The power converters, associated with the load they supply, generally constitute the power amplifier in a regulation loop. The flexibility of the computers, together with their capacity of treatment and storage allow their insertion at different levels of this loop, and the realization of different functions of fault detection of the power equipments, and of interaction with the operator. In order to test the faisability and the interest of such a disposal, we built a device to control a power converter with a microcomputer, using this one at two levels : the regulation of the ouput, and the elaboration of the control signals of the electronic switches. Furthermore, using informations given by well chosen sensors, the microcomputer detects and localizes possible failures; thanks to explicit messages given to the operator, it contributes to the maintainability of trie device. It also uses different strategies of control, according to the criteria of safety and fault tolerance which have been chosen.

Unified modelling of rectifier-controlled DC-power supplies

Abstract: The known analysis of dc/dc-converters in discontinuous operation mode and with voltage-commutation basing on piecewise linear description is extended to the analysis of line-commutated converters. Thereby as system-dependent pulse-widths the overlap angles appear, which can be computed in a manner analogous to the current flow duration and the reloading time respectively. This leads to an unified state space modelling of dc/dc- and ac/dc-converters by which the steady state and the dynamic small signal behavior can be evaluated directly. If the piecewisely defined system equations are integrated numerically, then by taking advantage of the structure of switched systems, a rather generalized way for the analysis of power converters results. As a first example a voltage-com-mutated dc/dc-converter with a non-linear dc-inductance is studied.

Optical branching device

Abstract: PURPOSE:To prevent the erroneous reception due to the delay of a branching device, by pairing optical fiber cables to constitute a network of a system and detecting a collision and the state of the network at the same time by a transmitting terminal. CONSTITUTION:Paired optical fibers 11 and 12, optical fibers 13 and 14, and optical fibers 15 and 16 through which optical information is transmitted are connected to a branching device 10 to constitute the communication network of the bus system. Photoelectric converters 17, 19, and 21 which convert optical information to an electric signal are connected to fibers 11, 13, and 15, and electrophoto converters 18, 20, and 22 which convert the electric signal to optical information are connected to fibers 12, 14, and 16. Outputs of converters 17 and 21 are supplied to an OR circuit 24, and the output of the circuit 24 is applied to the converter 20, and outputs of converters 19 and 21 are applied to an OR circuit 25, and the output of the circuit 25 is applied to the converter 18. Outputs of converters 17, 19, and 21 are applied to the converter 22 through an OR circuit 26. Thus, the erroneous reception due to the delay of the branching device 10, and the collision and the state of the network are detected at the same time by the transmitting terminal.

Applications of Magnetics to Problems in Switched-Mode Power Conversion

Abstract: Two topics are presented which advance the use of magnetic devices in switched-mode power converters. Part I discusses a novel method of detecting impending saturation of magnetic materials. The technique exploits the interaction of perpendicular magnetic fields to provide a simple, direct and continuous measure of the increasing nonlinearity of the material without any elaborate unconventional devices or complex electronic circuitry. Theoretical foundations and applications to ferrite cores in switching converters are given. Specific practical hardware examples are described including magnetics for a 4-kilowatt push-pull buck converter. Part II presents a discussion of the analysis of zero ripple integrated magnetic structures. These complex devices are of great interest in the field of switched mode power conversion because they have the ability to exclude ac currents from some of their windings when they are excited by ac voltages. A thorough analysis is carried out to establish which of the many characteristic parameters of these devices are responsible for the unusual zero ripple behavior. Practical methods of modelling and analysis are developed by which a designer can quickly determine the conditions required for zero ripple. Equivalent electric circuit models are given to aid in the electrical design of converters and to support the simple physical explanations of the observed phenomena including the effects of parasitic quantities. A number of experiments confirm the validity of the models.

Constant current device

Abstract: PURPOSE: To supply an accurate constant current by commonly controlling the time ratio of a plurality of resonance type constant current converters so that the output currents of the entire device become constant, thereby preventing the output current from decreasing upon increasing of the load CONSTITUTION: A plurality of resonance type constant current converters CONV are connected in series, and a current is supplied through a common current detector 6 to a load 9 The converters CONV have inverters 1, resonators 2, rectifying and smoothing circuits 3, and voltage/frequency converters 4 for controlling the operating frequencies of the inverters 1 The detector 6 detects the output current Iout of the entire device, compares it with a reference value by the controller CONT to control the converter 4 through a current/voltage converter 10 Thus, the inverters 1 are controlled by the common controller CONT, and the time ratio of the converters are controlled so as to become the prescribed constant current COPYRIGHT: (C)1985,JPO&Japio

A new control technique for ac-ac converters

Abstract: This work presents the fundamentals of a new control strategy for an AC-AC converter which uses power transistors in the switching mode as the main power elements and which connects directly the three-phase source to the load. This converter works with a fixed switching frequency and the modulation is performed by using a high-frequency dither (carrier) signal superimposed to a low-frequency control (modulating) voltage. The control strategy proposed here is based on the concept of Ficticious Bipolar Source. This concept is introduced in this work and it makes unnecessary the use of a direct current link for controlling this converter. The study is performed by considering that the converter is composed by controlled bi-directional switches. Preliminary results have been obtained via a digital simulation by using the Continuous System Modelling Program (CSMP). The control technique developed in this work allows to change the load frequency between 0 and more than 150 Hz; this output frequency is not limited by the frequency of the three-phase source. The low-frequency component of the load voltage can be varied continuously between 0 % and 100 %. The harmonics in the load and in the source currents can be easily removed by using simple filters. This converter presents no restrictions to the direction of power flow and it is well suited to be used in the four-quadrant speed control of DC and AC machines.

Analog-digital converting circuit

Abstract: PURPOSE:To obtain stably a high conversion bit number by combining comparators of an A/D converter in parallel and series so as to increase a signal voltage applied to one-stage of the comparators. CONSTITUTION:Four 6-bit momentary operation type A/D converters 1-4 are used, each operation reference voltage is operated while shifting by 1/4 LBS each, and output (6-bit) of the A/D converters 1-4 is added by full adders 5, 6 and an output (7-bit) of the full adders 5, 6 is added by a full adder 7 so as to obtain an 8-bit digital output of the converted bit number at an output terminal 23. Each operating voltage of n-set of N-bit momentary operation A/D converters is activated while shifting it by 1/n LBS, and all the digital signals (n-set) after the conversion is finished are added and the (N+log2n)-set of converting numbers are obtained.

Reactive-power machine for an energy supply device

Abstract: In an energy supply device, an on-board network (8) is supplied from a shaft generator (3) via static converters (4, 5, 6) and an inductance which is required for operating the converters. A reactive-power machine (7), into whose stator winding the inductance is integrated, is allocated to the static converter. The reactive-power machine (7) has two output connections (R1, R2; S1, S2; T1, T2; N1, N2) per line pole, the one set of connections (R1, S1, T1, N1) being connected to the output of the static converter, and the other set of connections (R2, S2, T2, N2) being connected to the on-board network (8).

Small-signal dynamic analysis of regulated Class-E DC/DC converters

Abstract: Class-E dc/dc converters can operate at high switching frequencies with very low switching power losses. Using commercially available power transistors and diodes, Class-E converters can operate at switching frequencies in the low-MHz range, with efficiencies of about 85%. Previous papers dealt with the circuit parameter values needed to obtain high-efficiency operation and output-voltage regulation, and with the static control characteristic of the Class-E dc/dc converter cell. Here we extend the analysis to include the dynamic control characteristics and further information about the static characteristics. The theoretical predictions are verified by experimental measurements on a 40-watt 1.5-MHz converter.

Electronic transformer composed of flyback converters

Abstract: An electronic transformer comprising first and second switching converters for converting the positive and negative half periods, respectively, of an input alternating voltage into high frequency voltages, which are rectified to produce an output alternating voltage at the input voltage frequency. The converters are constructed as fly-back converters with the choke coils as well as the output and input capacitors combined into elements common to the two respective high frequency fly-back converters. First and second backward diodes are connected parallel to each switching transistors of the two fly-back converters and each converter includes an auxiliary switching transistor switching at the input frequency to change over the converters from one half period to the other of the input AC voltage.

Digital/analogue converter

Abstract: Digital/analogue converters, particularly multiplying digital sin/cos converters (coordinate rotators, digital resolver converters) gain accuracy by operational amplifiers used. A particular drive of the switches related to the Gray code avoids transient error voltages (glitches) from being caused by the limited rise time of the operational amplifiers.

Balancing type frequency converter

Abstract: PURPOSE:To suppress a generated spurious at a signal output terminal by appling and adjusting independently a foward DC bias voltage to a diode of each frequency converter forming the frequency converter. CONSTITUTION:A balancing type frequency converter consists of 180 deg. hydrids 11, 13, an in-phase hybrid 12 for local power branching, and frequency converters 14, 15. VB1, VB2 are DC bias voltages to the converters 14, 15 respectively. In applying the DC bias voltage in the forward polarity of the diodes of the converters 14, 15, the converted loss of each output frequency component is changed. Then, the amplitude generated from both frequency converters is made coincident by taking notice of an optional spurious. Further, the phase is made coincident by inserting a phase adjusting circuit to a signal line or a local oscillating line. That is, the spurious at the output terminal is suppressed completely.

Automatic train stopping device

Abstract: PURPOSE:To provide rapid and accurate frequency comparing operation and to obtain a reliable fail-safe performance by converting via an F-DE converting function and a V-F converting function a train speed signal inputted in low frequency to a high frequency signal and doubling a speed signal series from a tachometer generator. CONSTITUTION:The same F-DC converters 14, 15 are connected to a tachometer generator TG, an analog switch 16 is connected to the converters, the same V-F converters 17, 18 are connected to the switch 15, the same frequency comparators 19, 20 are connected to the converters 17, 18 and an ATS pattern frequency generator 11, and an FF21 having set and reset terminals S, R is connected to the comparators 19, 20. When the switch 16 is switched, the converters 14, 17 are connected in series, a frequency signal indicating a train speed generated from the generator TG is converted by the converter 14 into a voltage, converted again to a frequency by the converter 17, and returned.