EPE Association: EPE 1995 - 42 - Dialogue Session DS5b: System Engineering

EPE 1995 - 42 - Dialogue Session DS5b: System Engineering
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1995 - Conference > EPE 1995 - 42 - Dialogue Session DS5b: System Engineering

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   NOVEL APPROACH TO AC/DC CONVERSION WITH NEAR TO UNITY POWER FACTOR
By L. Latkovskis; J. Stabulnieks [View]
[Download]

Abstract: The unity power factor of AC/DC converters is not optimum from the point of view of the output voltage ripple or RMS current of the output filter capacitor. Both of these parameters can be reduced by adding odd harmonies to the sinusoïdal current reference signal, at some increase of the input current distortion. The article deals with the results of theoretical investigations in that area. An optimum input current waveform which at the same power factor provides the minimum RMS current or voltage ripple of the capacitor is found.

   A SYMMETRICAL 3 PHASE-2 SWITCH PFC-POWER SUPPLY FOR VARIABLE OUTPUT VOLTAGE
By A.-Ch. Rufer; Ch.-B. Andrianirina [View]
[Download]

Abstract: Power Factor Corrected rectifiers are a new tendency in development of power supplies. In the last few years, a lot of R&D activities have led to a new category of products for one phase applications. In this contribution, a new simplified topology is proposed for three-phase applications, using only two active switches, and able to generate symmetrical currents in the line. Power and control circuits are presented. Complete simulation results with closed loop operation are given, as well as results of an experimental verification.

   DETERMINATION OF POWER FACTOR PREREGULATORS CONDUCTED EMI
By F. S. Dos Reis; J. Sebastian; J. Uceda [View]
[Download]

Abstract: In this paper, we will present a group of curves that allows us to determine the conducted Electromagnetic lnterference (EMI), generated for the basic PPP converters (éuk, Buck, Boost, Buck-Boost, Sepic, and Zeta converters). Using these curves we can determine the amplitude of the first harmonie in dB/μV in accordance with the CISPR 16 standard. Therefore, it can be an useful aid for filter designers.

   AN ORIGINAL DECOUPLING CAPACITOR
By Ch. Joubert; M. Lardellier; A. Beroual; G. Rojat [View]
[Download]

Abstract: This paper presents a new structure of connections of a metallized decoupling capacitor : a· four-terminal capacitor. It is shown that the use of such a capacitor allows to reduce the electromagnetic interferences and then to improve the high frequency performances of power electronics systems. The comparison of the efficiency of the filtering of a system in power electronics by means of this new structure shows an improvement of more than 20 dB attenuation in interference with regard to the performances achieved by traditional connections.

   INTEGRATED DIAGNOSTIC SYSTEMS FOR FAILURE IDENTIFICATION IN POWER CONVERTERS
By F. Filippetti; G. Franceschini; C. Tassoni [View]
[Download]

Abstract: A Voltage Source Inverter type converter, which supplies an induction actuator, is investigated as a typical configuration of commercial systems, in order to investigate on diagnostic systems design possibility. More usual long-term failure mechanisms are taken into account for the switching components in order to find significant variations, if any, in the monitoring variables which may lead to diagnostic indexes. These failure mechanisms lead to parameter variation in power semiconductors and the variations effects, if previously detected, should avoid catastrophic system faults. To explore this possibility the analysis of the impact of parameter changes on electric circuits variables is performed by computed simulation. To this aim suitable failure models for power devices are used.

   AN UNITY POWER FACTOR CONVERTOR WITHOUT CURRENT MEASUREMENT
By P. J. M. Smidt; J. L. Duarte [View]
[Download]

Abstract: This paper discusses an all-digital three-phase switching regulator. In particular, the focus here is on the application of principles of field orientation to obtain harmonic mitigation and power factor correction with minimal hardware. For this purpose, the utility grid is faced as being part of a virtual ac machine. The proposed approach does not require current measurement and provides a stabilized output voltage, being suited for operation at a fixed switching frequency. Experimental results concerning a 1 kW pre-conditioner verify the analysis.

   INDUCTION MOTORS RELIABILITY: USE OF A FAULT TREE
By P. Calonnec; T. Derrey; E. Destobbeleer; L. Protin [View]
[Download]

Abstract: The main principles of the functional analysis are first remembered. This analysis is used in this paper to study the reliability of an induction motor included in a variable speed drive. The main technical functions of the drive are described, then the induction motor can be considered as the studied system, the input and output technical functions of which have previously been studied. This is the starting point which allows the functional analysis of the induction motor and the representation of its general fault tree. In this general fault tree, the three main parts are precisely described, they are :
-the mechanical failure of the rotor,
-the rotor winding failure,
-the stator winding failure.
The use of an inverter to feed the induction motor is particularly taken into account in the analysis of the preceding types of failure.

   SINGLE PHASE ACTIVE FILTER POWER FACTOR CORRECTION
By B. Dakyo; J. C. Le Bunetel; L. Protin; W. Koczara [View]
[Download]

Abstract: The paper describes an innovative and active filtering power conditioning scheme based on a multistage boost topology, designed to achieve unity power factor. The concept uses a special differential control strategy and the ground idea consists of separating a required power flow into interdependent finite number of power levels. The convertor structure increases switching and power factor adjustment capability.

   THREE-PHASE PWM AC POWER CONTROLLER WITH (3+3) UNILATERAL SWITCHES
By R. Strzelecki; Z. Fedyczak [View]
[Download]

Abstract: ln this paper, an improved version of transistor-based power controller with a new by-pass suppressing circuit is analized and examined, in which a threshold overvoltage suppressor is used. In comparison with the previously reported solutions the proposed by-pass suppressing circuit enables the elimination of resonance phenomenon between the inductance of the source and the capacitance of the suppressor and the reduction of the power loss in the suppressor resistance, particularly in resistive-inductive load. Moreover, . the experimental results of the basic properties of a 25 kV A three-phase irnpuls power AC controller laboratory model with three modules with IGBT transistors are also presented in this paper.

   USE OF A VOLTAGE DIP AND UP SIMULATOR FOR TESTING THE TRANSIENT BEHAVIOUR OF A BIPOLAR POWER TRANSISTOR ARRAY BASED AC LINE VOLTAGE REGULATOR
By A.D.V.N. Kularatna; S.D. Godakumbura [View]
[Download]

Abstract: Transient behavior of an AC regulator is very important to determine the suitability of an AC voltage regulator for a given application. In the past, use of a series bipolar power transistor array for AC line voltage regulation bas been discussed as a practical methodology for .upgrading the performance of AC line regulators. In this type of a configuration, the transient behavior of the circuit technique is governed by the use of RMS/DC converters and the soft start/time delay circuits . In such a situation the transient behavior could be tested with a Voltage Dip and UP Simulator (VDUS). The article describes the methodology for using a VDUS for testing the transient behavior of a solid state AC regulator technique and utilising the data related to transient performance in practical circuit blacks with a view to optimize the design.

   AUTOMATIC GENERATION OF SOFTWARES FOR THE DESIGN OF STATIC CONVERTERS
By J.M. Bouche; F. Wurtz; L. Gerbaud [View]
[Download]

Abstract: As has already been shown, constrained CAD of static converters can be made by formulating a constrained design problem as a constrained optimization problem, Viarouge et al (1). The paper proposes a generic approach to automate the generation of such CAD softwares based on this principle. To programme informatically this process, a generator bas been built : PASCOSMA (for« Programme d' Analyse, de Synthèse, de Conception et d'Optimisation de système Modélisable Analytiquement » in French), which means « Program for analysis, design and optimisation of analytically modelled devices ». From design equations, given by experts or designers, PASCOSMA automatically builds a software to calculate inductances, capacitances, resistances and features or operating limits (eg: maximal values). On the one hand, the generator is based on symbolic calculus to generate the application and to formulate the equations. On the other hand, it uses an optimization module and has a graphic interface to make the use of the generated constrained design software easier for the electrotechnician.

   UNSEEN AND ERRATIC RISK IN POWER ELECTRONICS
By E. Blumschein [View]
[Download]

Abstract: Some exemplary cases of unseen and erratic risk in power electronic equipment are either reported from own experience or repoerted back from the Internet. They include erratic influences which stress the components, malfunctions due to miscellaneous reasons, and unseen dangerous effects. Recommendations are derived for recognition and prevention of such danger as well as for assessment and choice of control methods for switched mode power supplies.

   DESIGN OF A FULLY SOFT-SWITCHED EXTENDED PERIOD QUASI-RESONANT POWER FACTOR CORRECTION CIRCUIT
By S.Y.R. Hui; K.W.E. Cheng; S.R.N. Prakash [View]
[Download]

Abstract: This paper presents the design criteria, procedure and implementation of a softswitched power factor correction circuit based on the extended period quasi-resonant principles. All switches involved in the circuit are fully soft-switched. The design method is demonstrated in a prototype circuit. The operating principles are confirmed with computer simulation and experimental results.

   THERMAL RESISTANCE ANALYSIS BY INDUCED TRANSIENT METHOD (TRAIT) APPLIED TO POWER ELECTRONIC DEVICE PACKAGING
By P. E. Bagnoli; C. Casarosa; E. Dallago; A. Maiema; G. Sassone [View]
[Download]

Abstract: The TRAIT method consists of a new technique for characterising the equivalent thermal circuit of a .semiconductor power device and its packaging. It allows the experimental evaluation of the total thermal resistance as a sum of several contributions due to the various parts of the system. All the thermal capacitive component can be also evaluated. This method was applied to power integrated circuits mounted on assembling structures used for automotive electronics. Some purposely induced defects in the thermal properties of some parts of the structure was revealed and identified.

   COMPARATIVE DEPENDABILITY ANALYSIS OF ELECTRIC SHIP PROPULSION SYSTEMS
By G. Cosulich; M. Fracchia; A. Mariscotti; S. Savio [View]
[Download]

Abstract: Diesel electric propulsion systems are nowadays utilised in large cruise ships, icebreakers and special purpose vessels. In order to perform the optimum design of the electrical drive it's necessary to take into account the following factors: dependability, space saving and electric performances. The term dependability encompasses the concepts of reliability, availability, maintainability, safety and performability (the first four terms are commonly referred to as RAMS). Different electric configurations are analysed as far as dependability is concemed. The dependability study is performed by means of both combinatorial models and Petri nets simulation. This approach is useful at both design and validation stage.

   A KNOWLEDGE-BASED SYSTEM FOR ON-LINE FAULT DIAGNOSIS OF POWER INVERTER CIRCUITS FOR AC MACHINE DRIVE
By L. Zhang; I. B. Aris; L. N. Hulley [View]
[Download]

Abstract: Various types of faults in a power inverter for AC machine drives have been investigated. A knowledge-based fault diagnosis system has been built which can identify the nature and location of the faults through recognising the patterns of the three phase current at the machine input terminals. The structure of the system is described. Experimental and simulation results of a typical fault in the inverter are presented.

   LOSSES/EMI COMPROMISE RELATING TO ELECTRICAL CONSTRAINTS AND COMPONENTS TECHNOLOGY IN STATIC CONVERTERS
By Eric Labouré; François Costa; Maurice Lardellier; Gérard Rojat [View]
[Download]

Abstract: The method presented in this paper enables to optimise the compromise between losses and EMI level according to different electrical constraints or components technology in a switching cell. It enables also to characterise the behaviour of several switching cells, using association rules. Experimental results have proved the availability of this method.

   CERTAIN OVERLOADING PROTECTION OF THREE-PHASE AC ELECTRICAL MOTORS, USING ELECTRONIC RELAYS
By C. Ghita; M. Staicu; A. Bocse; V. Burtea [View]
[Download]

Abstract: This paper presents the electric scheme and the experimental testing of an electronic relay for the overloading protection of AC electrical motors. The patterns heating and cooling temperature curves for a certain motor are modelled by the output voltage of an integrator circuit, based on the supply current of the motor. The relay follows the average temperature of the motor for any operating state, and breaks the supplying when reached the e* protection temperature. Heating and cooling curves of the motor are previously required, in order to choose the relay parameters for optimal operating. Experimental tests show the fact that, the temperature and the humidity of the environment where the motor is placed, does not have a significant influence on the relay's performing.

   FOUR-WIRE POWER FACTOR CORRECTED BOOST RECTIFIER
By M.E. Fraser; C.D. Manning [View]
[Download]

Abstract: This paper introduces a new four-wire, three-phase, power factor corrected, reversible rectifier which does not require a transformer and does not draw low order harmonics from the supply neutral. The topology, operating principles and control are discussed as well as a guide to choose the values of the filters and control parameters. Simulation results will show the steady-state and dynamic performance of the rectifier.

   MODELLING OF CONDUCTED EMI
By F. Klotz; J. Petzoldt [View]
[Download]

Abstract: This paper deals with conducted electromagnetic interference emissions produced by power electronic circuits. The results of different experimental investigations are presented in dependence of several influences on the interference spectra. For the tested chopper structure and others topologies like DC-DC PWM converters an equivalent circuit is derived for the prediction of the interference level. The model simultaneouse calculates both conducted EMI phenomena the common and the differential mode currents and voltages. The results of simulations are compared with experimentally measured interference spectra. The several influences of the active and passive elements are discussed.

   FLYBACK CONVERTER WITH CAPACITIVELY COUPLED BOOST POWER STAGE
By M. Albach [View]
[Download]

Abstract: This report describes an integrated solution of a conventional mains isolated dc-dc flyback converter with an ac-dc boost power stage. As the choke and the freewheeling diode of the boost stage are connected via a capacitor to a hf voltage source in the dc-dc converter the separate switch of the boost circuit is avoided. By means of the specific circuit configuration this coupling capacitor is simultaneously used as a dV/dt limiter for the main switch in the flyback converter and allows to recover the energy from the leakage inductance of the transformer. With an additional low power switch and a second capacitor a lossless voltage clamp can be realized.

EPE 1995 - 42 - Dialogue Session DS5b: System Engineering
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1995 - Conference > EPE 1995 - 42 - Dialogue Session DS5b: System Engineering
	[return to parent folder]

	NOVEL APPROACH TO AC/DC CONVERSION WITH NEAR TO UNITY POWER FACTOR By L. Latkovskis; J. Stabulnieks	[View] [Download]
Abstract: The unity power factor of AC/DC converters is not optimum from the point of view of the output voltage ripple or RMS current of the output filter capacitor. Both of these parameters can be reduced by adding odd harmonies to the sinusoïdal current reference signal, at some increase of the input current distortion. The article deals with the results of theoretical investigations in that area. An optimum input current waveform which at the same power factor provides the minimum RMS current or voltage ripple of the capacitor is found.

	A SYMMETRICAL 3 PHASE-2 SWITCH PFC-POWER SUPPLY FOR VARIABLE OUTPUT VOLTAGE By A.-Ch. Rufer; Ch.-B. Andrianirina	[View] [Download]
Abstract: Power Factor Corrected rectifiers are a new tendency in development of power supplies. In the last few years, a lot of R&D activities have led to a new category of products for one phase applications. In this contribution, a new simplified topology is proposed for three-phase applications, using only two active switches, and able to generate symmetrical currents in the line. Power and control circuits are presented. Complete simulation results with closed loop operation are given, as well as results of an experimental verification.

	DETERMINATION OF POWER FACTOR PREREGULATORS CONDUCTED EMI By F. S. Dos Reis; J. Sebastian; J. Uceda	[View] [Download]
Abstract: In this paper, we will present a group of curves that allows us to determine the conducted Electromagnetic lnterference (EMI), generated for the basic PPP converters (éuk, Buck, Boost, Buck-Boost, Sepic, and Zeta converters). Using these curves we can determine the amplitude of the first harmonie in dB/μV in accordance with the CISPR 16 standard. Therefore, it can be an useful aid for filter designers.

	AN ORIGINAL DECOUPLING CAPACITOR By Ch. Joubert; M. Lardellier; A. Beroual; G. Rojat	[View] [Download]
Abstract: This paper presents a new structure of connections of a metallized decoupling capacitor : a· four-terminal capacitor. It is shown that the use of such a capacitor allows to reduce the electromagnetic interferences and then to improve the high frequency performances of power electronics systems. The comparison of the efficiency of the filtering of a system in power electronics by means of this new structure shows an improvement of more than 20 dB attenuation in interference with regard to the performances achieved by traditional connections.

	INTEGRATED DIAGNOSTIC SYSTEMS FOR FAILURE IDENTIFICATION IN POWER CONVERTERS By F. Filippetti; G. Franceschini; C. Tassoni	[View] [Download]
Abstract: A Voltage Source Inverter type converter, which supplies an induction actuator, is investigated as a typical configuration of commercial systems, in order to investigate on diagnostic systems design possibility. More usual long-term failure mechanisms are taken into account for the switching components in order to find significant variations, if any, in the monitoring variables which may lead to diagnostic indexes. These failure mechanisms lead to parameter variation in power semiconductors and the variations effects, if previously detected, should avoid catastrophic system faults. To explore this possibility the analysis of the impact of parameter changes on electric circuits variables is performed by computed simulation. To this aim suitable failure models for power devices are used.

	AN UNITY POWER FACTOR CONVERTOR WITHOUT CURRENT MEASUREMENT By P. J. M. Smidt; J. L. Duarte	[View] [Download]
Abstract: This paper discusses an all-digital three-phase switching regulator. In particular, the focus here is on the application of principles of field orientation to obtain harmonic mitigation and power factor correction with minimal hardware. For this purpose, the utility grid is faced as being part of a virtual ac machine. The proposed approach does not require current measurement and provides a stabilized output voltage, being suited for operation at a fixed switching frequency. Experimental results concerning a 1 kW pre-conditioner verify the analysis.

	INDUCTION MOTORS RELIABILITY: USE OF A FAULT TREE By P. Calonnec; T. Derrey; E. Destobbeleer; L. Protin	[View] [Download]
Abstract: The main principles of the functional analysis are first remembered. This analysis is used in this paper to study the reliability of an induction motor included in a variable speed drive. The main technical functions of the drive are described, then the induction motor can be considered as the studied system, the input and output technical functions of which have previously been studied. This is the starting point which allows the functional analysis of the induction motor and the representation of its general fault tree. In this general fault tree, the three main parts are precisely described, they are : -the mechanical failure of the rotor, -the rotor winding failure, -the stator winding failure. The use of an inverter to feed the induction motor is particularly taken into account in the analysis of the preceding types of failure.

	SINGLE PHASE ACTIVE FILTER POWER FACTOR CORRECTION By B. Dakyo; J. C. Le Bunetel; L. Protin; W. Koczara	[View] [Download]
Abstract: The paper describes an innovative and active filtering power conditioning scheme based on a multistage boost topology, designed to achieve unity power factor. The concept uses a special differential control strategy and the ground idea consists of separating a required power flow into interdependent finite number of power levels. The convertor structure increases switching and power factor adjustment capability.

	THREE-PHASE PWM AC POWER CONTROLLER WITH (3+3) UNILATERAL SWITCHES By R. Strzelecki; Z. Fedyczak	[View] [Download]
Abstract: ln this paper, an improved version of transistor-based power controller with a new by-pass suppressing circuit is analized and examined, in which a threshold overvoltage suppressor is used. In comparison with the previously reported solutions the proposed by-pass suppressing circuit enables the elimination of resonance phenomenon between the inductance of the source and the capacitance of the suppressor and the reduction of the power loss in the suppressor resistance, particularly in resistive-inductive load. Moreover, . the experimental results of the basic properties of a 25 kV A three-phase irnpuls power AC controller laboratory model with three modules with IGBT transistors are also presented in this paper.

	USE OF A VOLTAGE DIP AND UP SIMULATOR FOR TESTING THE TRANSIENT BEHAVIOUR OF A BIPOLAR POWER TRANSISTOR ARRAY BASED AC LINE VOLTAGE REGULATOR By A.D.V.N. Kularatna; S.D. Godakumbura	[View] [Download]
Abstract: Transient behavior of an AC regulator is very important to determine the suitability of an AC voltage regulator for a given application. In the past, use of a series bipolar power transistor array for AC line voltage regulation bas been discussed as a practical methodology for .upgrading the performance of AC line regulators. In this type of a configuration, the transient behavior of the circuit technique is governed by the use of RMS/DC converters and the soft start/time delay circuits . In such a situation the transient behavior could be tested with a Voltage Dip and UP Simulator (VDUS). The article describes the methodology for using a VDUS for testing the transient behavior of a solid state AC regulator technique and utilising the data related to transient performance in practical circuit blacks with a view to optimize the design.

	AUTOMATIC GENERATION OF SOFTWARES FOR THE DESIGN OF STATIC CONVERTERS By J.M. Bouche; F. Wurtz; L. Gerbaud	[View] [Download]
Abstract: As has already been shown, constrained CAD of static converters can be made by formulating a constrained design problem as a constrained optimization problem, Viarouge et al (1). The paper proposes a generic approach to automate the generation of such CAD softwares based on this principle. To programme informatically this process, a generator bas been built : PASCOSMA (for« Programme d' Analyse, de Synthèse, de Conception et d'Optimisation de système Modélisable Analytiquement » in French), which means « Program for analysis, design and optimisation of analytically modelled devices ». From design equations, given by experts or designers, PASCOSMA automatically builds a software to calculate inductances, capacitances, resistances and features or operating limits (eg: maximal values). On the one hand, the generator is based on symbolic calculus to generate the application and to formulate the equations. On the other hand, it uses an optimization module and has a graphic interface to make the use of the generated constrained design software easier for the electrotechnician.

	UNSEEN AND ERRATIC RISK IN POWER ELECTRONICS By E. Blumschein	[View] [Download]
Abstract: Some exemplary cases of unseen and erratic risk in power electronic equipment are either reported from own experience or repoerted back from the Internet. They include erratic influences which stress the components, malfunctions due to miscellaneous reasons, and unseen dangerous effects. Recommendations are derived for recognition and prevention of such danger as well as for assessment and choice of control methods for switched mode power supplies.

	DESIGN OF A FULLY SOFT-SWITCHED EXTENDED PERIOD QUASI-RESONANT POWER FACTOR CORRECTION CIRCUIT By S.Y.R. Hui; K.W.E. Cheng; S.R.N. Prakash	[View] [Download]
Abstract: This paper presents the design criteria, procedure and implementation of a softswitched power factor correction circuit based on the extended period quasi-resonant principles. All switches involved in the circuit are fully soft-switched. The design method is demonstrated in a prototype circuit. The operating principles are confirmed with computer simulation and experimental results.

	THERMAL RESISTANCE ANALYSIS BY INDUCED TRANSIENT METHOD (TRAIT) APPLIED TO POWER ELECTRONIC DEVICE PACKAGING By P. E. Bagnoli; C. Casarosa; E. Dallago; A. Maiema; G. Sassone	[View] [Download]
Abstract: The TRAIT method consists of a new technique for characterising the equivalent thermal circuit of a .semiconductor power device and its packaging. It allows the experimental evaluation of the total thermal resistance as a sum of several contributions due to the various parts of the system. All the thermal capacitive component can be also evaluated. This method was applied to power integrated circuits mounted on assembling structures used for automotive electronics. Some purposely induced defects in the thermal properties of some parts of the structure was revealed and identified.

	COMPARATIVE DEPENDABILITY ANALYSIS OF ELECTRIC SHIP PROPULSION SYSTEMS By G. Cosulich; M. Fracchia; A. Mariscotti; S. Savio	[View] [Download]
Abstract: Diesel electric propulsion systems are nowadays utilised in large cruise ships, icebreakers and special purpose vessels. In order to perform the optimum design of the electrical drive it's necessary to take into account the following factors: dependability, space saving and electric performances. The term dependability encompasses the concepts of reliability, availability, maintainability, safety and performability (the first four terms are commonly referred to as RAMS). Different electric configurations are analysed as far as dependability is concemed. The dependability study is performed by means of both combinatorial models and Petri nets simulation. This approach is useful at both design and validation stage.

	A KNOWLEDGE-BASED SYSTEM FOR ON-LINE FAULT DIAGNOSIS OF POWER INVERTER CIRCUITS FOR AC MACHINE DRIVE By L. Zhang; I. B. Aris; L. N. Hulley	[View] [Download]
Abstract: Various types of faults in a power inverter for AC machine drives have been investigated. A knowledge-based fault diagnosis system has been built which can identify the nature and location of the faults through recognising the patterns of the three phase current at the machine input terminals. The structure of the system is described. Experimental and simulation results of a typical fault in the inverter are presented.

	LOSSES/EMI COMPROMISE RELATING TO ELECTRICAL CONSTRAINTS AND COMPONENTS TECHNOLOGY IN STATIC CONVERTERS By Eric Labouré; François Costa; Maurice Lardellier; Gérard Rojat	[View] [Download]
Abstract: The method presented in this paper enables to optimise the compromise between losses and EMI level according to different electrical constraints or components technology in a switching cell. It enables also to characterise the behaviour of several switching cells, using association rules. Experimental results have proved the availability of this method.

	CERTAIN OVERLOADING PROTECTION OF THREE-PHASE AC ELECTRICAL MOTORS, USING ELECTRONIC RELAYS By C. Ghita; M. Staicu; A. Bocse; V. Burtea	[View] [Download]
Abstract: This paper presents the electric scheme and the experimental testing of an electronic relay for the overloading protection of AC electrical motors. The patterns heating and cooling temperature curves for a certain motor are modelled by the output voltage of an integrator circuit, based on the supply current of the motor. The relay follows the average temperature of the motor for any operating state, and breaks the supplying when reached the e* protection temperature. Heating and cooling curves of the motor are previously required, in order to choose the relay parameters for optimal operating. Experimental tests show the fact that, the temperature and the humidity of the environment where the motor is placed, does not have a significant influence on the relay's performing.

	FOUR-WIRE POWER FACTOR CORRECTED BOOST RECTIFIER By M.E. Fraser; C.D. Manning	[View] [Download]
Abstract: This paper introduces a new four-wire, three-phase, power factor corrected, reversible rectifier which does not require a transformer and does not draw low order harmonics from the supply neutral. The topology, operating principles and control are discussed as well as a guide to choose the values of the filters and control parameters. Simulation results will show the steady-state and dynamic performance of the rectifier.

	MODELLING OF CONDUCTED EMI By F. Klotz; J. Petzoldt	[View] [Download]
Abstract: This paper deals with conducted electromagnetic interference emissions produced by power electronic circuits. The results of different experimental investigations are presented in dependence of several influences on the interference spectra. For the tested chopper structure and others topologies like DC-DC PWM converters an equivalent circuit is derived for the prediction of the interference level. The model simultaneouse calculates both conducted EMI phenomena the common and the differential mode currents and voltages. The results of simulations are compared with experimentally measured interference spectra. The several influences of the active and passive elements are discussed.

	FLYBACK CONVERTER WITH CAPACITIVELY COUPLED BOOST POWER STAGE By M. Albach	[View] [Download]
Abstract: This report describes an integrated solution of a conventional mains isolated dc-dc flyback converter with an ac-dc boost power stage. As the choke and the freewheeling diode of the boost stage are connected via a capacitor to a hf voltage source in the dc-dc converter the separate switch of the boost circuit is avoided. By means of the specific circuit configuration this coupling capacitor is simultaneously used as a dV/dt limiter for the main switch in the flyback converter and allows to recover the energy from the leakage inductance of the transformer. With an additional low power switch and a second capacitor a lossless voltage clamp can be realized.