EPE Association: EPE 1985 - 31 - Dialogue Session 1.1: DIALOGUE / POSTER SESSION (I)

EPE 1985 - 31 - Dialogue Session 1.1: DIALOGUE / POSTER SESSION (I)
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1985 - Conference > EPE 1985 - 31 - Dialogue Session 1.1: DIALOGUE / POSTER SESSION (I)

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   ELECTROMAGNETIC REACTIVE POWER COMPENSATOR
By P. Jovanovic; N. Behlilovic [View]
[Download]

Abstract: The paper presents some results obtained in the development of a new type of static compensators - electromagnetic compensators for continual regulation of reactive power / EK /. The paper, in addition, presents the developed mathematical model for EK in its most general form, which covers both steady state and transient processes for all essential parameters of voltages and currents as well as for their vector shifts for various types of inductive and capacitive loads. The results of experimental research on constructed EK have also been presented and compared with the results obtained from this new universal mathematical model. Experimental and computer results show that the developed EK exhibit, in addition to their basic task - the requlation / automatic or programmed / of industrial consumers, high technical, economical and other performances / very high speed of regulation and low distortion factor of primary and secondary voltage, very high efficiency, insensitivity to overvoltages and overloads, and the capability of direct operation on high voltage without intermediate transformation and remarkably less cost effective than the thyristor compensators /.

   HIGH SWITCHING FREQUENCY PWM THYRISTOR INVERTER FOR 60 KVA APPLICATIONS
By R. De Doncker; A. Vandenput; W. Geysen [View]
[Download]

Abstract: The construction of the power electronic circuits of a 60 kVA (380 Vac at 50 Hz) PWM inverter has to meet the needs of modern PWM circuits and digital feed forward controllers (FFC). The most important demands, as for instance highest switching frequency, minimum pulse width of the inverter and the necessity of independent control (for the FFC) of the average voltage and frequency, have their impact on the choice of power thyristors, the circuit lay-out and the drive circuits.

   PHASE CONTROL OF A DISC-ARMATURE LINEAR TWO-PHASE SERVOMOTOR
By V. Iancu; V. Trifa [View]
[Download]

Abstract: The paper presents a disc-armature linear two-phase servomotor, controlled by an electronic phase variator. Construction principle and means of speed control are described. In this paper only the phase control of servomotor is studied. In this purpose the structure of the phase variator and its performances are shown. The servomotor driven by the phase variator is experimentally tested. The waveforms of the main signals inside the variator, as well as output currents are given. Also, dynamic regimes of servomotor are experimented, taking the output voltage of a linear two-phase tachogenerator as measure of rotational speed.

   TECHNOLOGY OF SMALL POWER-INVERTERS WITH MOSFET-TRANSISTORS
By D. Baert; H. Kuyken; P. De Visschere [View]
[Download]

Abstract: Due to the high switching frequencies the design of pulse-width modulated mosfet power transistor converters or inverters shows several difficulties. The high-frequency transformer has to have an extremely low leakage inductance and low rasistance in order to reduce voltage transients and to increase the efficiency. Careful design of the p.c. board is also important because of the fast high-current pulses.

   OPTIMATION PROCEDURE FOR BRIDGE INVERTER SNUBBERS FOR AC DRIVES
By M. Alonso; J. Peire; F. Aldana [View]
[Download]

Abstract: In this paper a procedure for selecting optimum first order polarized and not polarized RC snubbers for bridge inverters is presented. These snubbers need to be connected across power rectifiers to absorb the energy associated with the recovery current of the device and limit the resulting voltage spike and rate of rise du/dt. In order to select the optimum resistance and capacitance the additional losses introduced by the snubber are also considered. The basis of this study is performed through the results of the SPICE2 (computer simulation program) (Nagel, 1975) (Vladimirescu, 1980). The best power switches device models (diode, transistor and SCR) for this study, as well as general guidelines for parameter definition are proposed.

   SINGLE-STAGE POLY-PHASE TO SINGLE-PHASE CONVERSION USING MULTILEVEL PWM TECHNIQUE
By L. Malesani; P. Tenti [View]
[Download]

Abstract: The performance of a fully-controlled three-phase to sinqle-phase cycloconverter is analyzed. It is controlled accordinq to a multilevel PWM technique aimed to optimize the output voltaqe waveform. Theoretical relationships are derived and calculations are performed on the input current waveforms and their harmonic contents. Input current spectra are qiven as a function of the amplitude, frequency and phase of the load voltage and current. Experimental results obtained from a prototype are finally reported.

   FLYBACK CONVERTER OUTPUT VOLTAGE STABILIZATION
By S. Birca-Galateanu [View]
[Download]

Abstract: The expression of the flyback converter output voltage (output power) is deduced in function of the supply voltage, load resistance, transformer ratios, transistor current gain and base circuit resistor value. Switching period and duty cycle are also calculated. A converter circuit is designed having stabilized output voltage with respect to supply voltage, at constant load. The transistor base current is controlled by the supply voltage, via a nonlinear circuit. This " feedforward " circuit approximates with a logarithmic characteristics the ideal hyperbolic dependance of the transistor base current in function of the supply voltage. The converter has high performances and low cost.

   STATIC FREQUENCY CONVERTERS FOR DRIVING THE ROLLING MILLS ROLLS
By D. Alexa; L. Turic; M. Antonescu [View]
[Download]

Abstract: In this paper, the command principle is described for a static frequency converter having only one LC commutation circuit and a small number of thyristors and diodes. This principle permits to obtain stepped output voltages with twelve pulses having the content of the fundamental harmonic equal to 0,986. The operating principle is described and the analysis of the higher harmonics spectrum of the output voltage is made.

   A CONTRIBUTION TO THE OPTIMALIZATION OF THE OUTPUT LC FILTER AT THE CONSTANT FREQUENCY AND TWO LEVEL CONTROLLED INVERTERS
By A. Stofanik [View]
[Download]

Abstract: A pulse width modulated (PWM) inverter without expressed carrier frequency generator represents a nonlinear oscillating feedback circuit in which rise the selfoscillations. Such inverter can be characterized as a two level controlled system. The present paper deals with the description of the operation, method of analyse and achieved results at the such inverter type in case of a passive resistance load. The matter of the analysis is to derive the common valid equations among the part circuit values, external voltages, load and electrical inverter parameters to gain the basis for the optimal synthesis of the output LC filters.The following method was employed:
- The analytic expressions were derived for the voltage and current responses in the steady-state operation.
- The analysis of the derived expressions was performed.
- The graphical dependences suitable for the synthesis of the optimal LC filters and working areas of inverters were gained by calculating of the analytic expressions.

   COMPUTER AIDED EVALUATION OF SOME DESIGN PROBLEMS OF SCR CHOPPERS
By A. Barili; A. Brambilla; G. Cottafava; E. Dallago; U. Mauri; R. Romano; E. Marelli [View]
[Download]

Abstract: An SCR model was implemented at the Pavia University on the SPICE networks simulator. It has been extensively used to test some design problems concerning the realization of an SCR dc-to-dc converter (chopper), used in electrical railway. A power electronic simulator allows quick electrical analysis of the whole chopper system. Therefore the designer may change design parameters of subcircuits in order to explore their influence on the system behaviour. This paper considers specially the following topics: SCR switching phenomena, parasitic effects on switching and RC snubber circuits. Simulation results are checked against experimental ones.

   CURRENT DISTRIBUTION ANALYSIS OF REVERSE PARALLEL THYRISTORS IN LOW VOLTAGE BREAKER
By T. B. Stavrakeva [View]
[Download]

Abstract: The transient process at thyristor parallel operation in low voltage breakers is investigated, when the transformer current equalising elements are used. The nonlinear character of the thyristors and reactors is considered. An algorithm and computer Fortran programme is compiled for a determination of the instantaneous current values into the parallel branches. The experiments undertaken confirm the thereotical results.

   ON DEVELOPMENT OF HVDC CONVERTER SYSTEMS
By A. I. Said [View]
[Download]

Abstract: At present, the high-voltage direct-current (HVDC) electric power systems are more simple in operation or planning compared to AC systems and they become more competitive, more practical and more economical. The development ot HVDC converter systems using high voltage thyristors has also opened new possibilities for better optimisation of the system. This article presents some aspects on the design and development possibilities of HVDC systems and their future requirements for converter valves. Future applications are discussed with special emphasis on economic aspects, design of converter control, availability and reliability of the system with its other auxiliary equipment. The article concludes with a presentation of thyristor valve protection and testing procedures for both normal operation and fault conditions.

   COMMUTATION COIL COUPLING FACTOR INFLUENCE ON THE INVERTER OPERATION
By S. Darie; H. Balan [View]
[Download]

Abstract: The paper deals with bridge-type single-phase voltage source inverters supplying oscillomotors. By employing a lead current commutation analysis, the dependence of turn-off groups upon the coil coupling factor is studied. On the line of previous publications (McMurray and Shattuck, 1961; Cerbulescu, 1983) the authors propose turn-off group design diagrams in function of the coil coupling factor for usual values of the d.c. supply voltage (Uo), lead current (is) and thyristor recovery time (tq).

   PWM DC / DC CONVERTERS : A STRAIGHTFORWARD EVALUATION OF THEIR DC LOOP-GAIN
By C. Burgio; P. Cammelli; P. Maranesi; V. Varoli [View]
[Download]

Abstract: The D.C. loop-gains of the basic PWM DC/DC converters are deduced by means of charge and energy balances and Campbell theorem. Discontinuous and continuous operation in both the Duty-Cycle Control Mode and the Current Control Mode are analyzed and complete expressions of relevant D.C. gains are given. The most peculiar results refer to the DCM/CCM transition and to some oddnesses of the Current-Control Mode.

EPE 1985 - 31 - Dialogue Session 1.1: DIALOGUE / POSTER SESSION (I)
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1985 - Conference > EPE 1985 - 31 - Dialogue Session 1.1: DIALOGUE / POSTER SESSION (I)
	[return to parent folder]

	ELECTROMAGNETIC REACTIVE POWER COMPENSATOR By P. Jovanovic; N. Behlilovic	[View] [Download]
Abstract: The paper presents some results obtained in the development of a new type of static compensators - electromagnetic compensators for continual regulation of reactive power / EK /. The paper, in addition, presents the developed mathematical model for EK in its most general form, which covers both steady state and transient processes for all essential parameters of voltages and currents as well as for their vector shifts for various types of inductive and capacitive loads. The results of experimental research on constructed EK have also been presented and compared with the results obtained from this new universal mathematical model. Experimental and computer results show that the developed EK exhibit, in addition to their basic task - the requlation / automatic or programmed / of industrial consumers, high technical, economical and other performances / very high speed of regulation and low distortion factor of primary and secondary voltage, very high efficiency, insensitivity to overvoltages and overloads, and the capability of direct operation on high voltage without intermediate transformation and remarkably less cost effective than the thyristor compensators /.

	HIGH SWITCHING FREQUENCY PWM THYRISTOR INVERTER FOR 60 KVA APPLICATIONS By R. De Doncker; A. Vandenput; W. Geysen	[View] [Download]
Abstract: The construction of the power electronic circuits of a 60 kVA (380 Vac at 50 Hz) PWM inverter has to meet the needs of modern PWM circuits and digital feed forward controllers (FFC). The most important demands, as for instance highest switching frequency, minimum pulse width of the inverter and the necessity of independent control (for the FFC) of the average voltage and frequency, have their impact on the choice of power thyristors, the circuit lay-out and the drive circuits.

	PHASE CONTROL OF A DISC-ARMATURE LINEAR TWO-PHASE SERVOMOTOR By V. Iancu; V. Trifa	[View] [Download]
Abstract: The paper presents a disc-armature linear two-phase servomotor, controlled by an electronic phase variator. Construction principle and means of speed control are described. In this paper only the phase control of servomotor is studied. In this purpose the structure of the phase variator and its performances are shown. The servomotor driven by the phase variator is experimentally tested. The waveforms of the main signals inside the variator, as well as output currents are given. Also, dynamic regimes of servomotor are experimented, taking the output voltage of a linear two-phase tachogenerator as measure of rotational speed.

	TECHNOLOGY OF SMALL POWER-INVERTERS WITH MOSFET-TRANSISTORS By D. Baert; H. Kuyken; P. De Visschere	[View] [Download]
Abstract: Due to the high switching frequencies the design of pulse-width modulated mosfet power transistor converters or inverters shows several difficulties. The high-frequency transformer has to have an extremely low leakage inductance and low rasistance in order to reduce voltage transients and to increase the efficiency. Careful design of the p.c. board is also important because of the fast high-current pulses.

	OPTIMATION PROCEDURE FOR BRIDGE INVERTER SNUBBERS FOR AC DRIVES By M. Alonso; J. Peire; F. Aldana	[View] [Download]
Abstract: In this paper a procedure for selecting optimum first order polarized and not polarized RC snubbers for bridge inverters is presented. These snubbers need to be connected across power rectifiers to absorb the energy associated with the recovery current of the device and limit the resulting voltage spike and rate of rise du/dt. In order to select the optimum resistance and capacitance the additional losses introduced by the snubber are also considered. The basis of this study is performed through the results of the SPICE2 (computer simulation program) (Nagel, 1975) (Vladimirescu, 1980). The best power switches device models (diode, transistor and SCR) for this study, as well as general guidelines for parameter definition are proposed.

	SINGLE-STAGE POLY-PHASE TO SINGLE-PHASE CONVERSION USING MULTILEVEL PWM TECHNIQUE By L. Malesani; P. Tenti	[View] [Download]
Abstract: The performance of a fully-controlled three-phase to sinqle-phase cycloconverter is analyzed. It is controlled accordinq to a multilevel PWM technique aimed to optimize the output voltaqe waveform. Theoretical relationships are derived and calculations are performed on the input current waveforms and their harmonic contents. Input current spectra are qiven as a function of the amplitude, frequency and phase of the load voltage and current. Experimental results obtained from a prototype are finally reported.

	FLYBACK CONVERTER OUTPUT VOLTAGE STABILIZATION By S. Birca-Galateanu	[View] [Download]
Abstract: The expression of the flyback converter output voltage (output power) is deduced in function of the supply voltage, load resistance, transformer ratios, transistor current gain and base circuit resistor value. Switching period and duty cycle are also calculated. A converter circuit is designed having stabilized output voltage with respect to supply voltage, at constant load. The transistor base current is controlled by the supply voltage, via a nonlinear circuit. This " feedforward " circuit approximates with a logarithmic characteristics the ideal hyperbolic dependance of the transistor base current in function of the supply voltage. The converter has high performances and low cost.

	STATIC FREQUENCY CONVERTERS FOR DRIVING THE ROLLING MILLS ROLLS By D. Alexa; L. Turic; M. Antonescu	[View] [Download]
Abstract: In this paper, the command principle is described for a static frequency converter having only one LC commutation circuit and a small number of thyristors and diodes. This principle permits to obtain stepped output voltages with twelve pulses having the content of the fundamental harmonic equal to 0,986. The operating principle is described and the analysis of the higher harmonics spectrum of the output voltage is made.

	A CONTRIBUTION TO THE OPTIMALIZATION OF THE OUTPUT LC FILTER AT THE CONSTANT FREQUENCY AND TWO LEVEL CONTROLLED INVERTERS By A. Stofanik	[View] [Download]
Abstract: A pulse width modulated (PWM) inverter without expressed carrier frequency generator represents a nonlinear oscillating feedback circuit in which rise the selfoscillations. Such inverter can be characterized as a two level controlled system. The present paper deals with the description of the operation, method of analyse and achieved results at the such inverter type in case of a passive resistance load. The matter of the analysis is to derive the common valid equations among the part circuit values, external voltages, load and electrical inverter parameters to gain the basis for the optimal synthesis of the output LC filters.The following method was employed: - The analytic expressions were derived for the voltage and current responses in the steady-state operation. - The analysis of the derived expressions was performed. - The graphical dependences suitable for the synthesis of the optimal LC filters and working areas of inverters were gained by calculating of the analytic expressions.

	COMPUTER AIDED EVALUATION OF SOME DESIGN PROBLEMS OF SCR CHOPPERS By A. Barili; A. Brambilla; G. Cottafava; E. Dallago; U. Mauri; R. Romano; E. Marelli	[View] [Download]
Abstract: An SCR model was implemented at the Pavia University on the SPICE networks simulator. It has been extensively used to test some design problems concerning the realization of an SCR dc-to-dc converter (chopper), used in electrical railway. A power electronic simulator allows quick electrical analysis of the whole chopper system. Therefore the designer may change design parameters of subcircuits in order to explore their influence on the system behaviour. This paper considers specially the following topics: SCR switching phenomena, parasitic effects on switching and RC snubber circuits. Simulation results are checked against experimental ones.

	CURRENT DISTRIBUTION ANALYSIS OF REVERSE PARALLEL THYRISTORS IN LOW VOLTAGE BREAKER By T. B. Stavrakeva	[View] [Download]
Abstract: The transient process at thyristor parallel operation in low voltage breakers is investigated, when the transformer current equalising elements are used. The nonlinear character of the thyristors and reactors is considered. An algorithm and computer Fortran programme is compiled for a determination of the instantaneous current values into the parallel branches. The experiments undertaken confirm the thereotical results.

	ON DEVELOPMENT OF HVDC CONVERTER SYSTEMS By A. I. Said	[View] [Download]
Abstract: At present, the high-voltage direct-current (HVDC) electric power systems are more simple in operation or planning compared to AC systems and they become more competitive, more practical and more economical. The development ot HVDC converter systems using high voltage thyristors has also opened new possibilities for better optimisation of the system. This article presents some aspects on the design and development possibilities of HVDC systems and their future requirements for converter valves. Future applications are discussed with special emphasis on economic aspects, design of converter control, availability and reliability of the system with its other auxiliary equipment. The article concludes with a presentation of thyristor valve protection and testing procedures for both normal operation and fault conditions.

	COMMUTATION COIL COUPLING FACTOR INFLUENCE ON THE INVERTER OPERATION By S. Darie; H. Balan	[View] [Download]
Abstract: The paper deals with bridge-type single-phase voltage source inverters supplying oscillomotors. By employing a lead current commutation analysis, the dependence of turn-off groups upon the coil coupling factor is studied. On the line of previous publications (McMurray and Shattuck, 1961; Cerbulescu, 1983) the authors propose turn-off group design diagrams in function of the coil coupling factor for usual values of the d.c. supply voltage (Uo), lead current (is) and thyristor recovery time (tq).

	PWM DC / DC CONVERTERS : A STRAIGHTFORWARD EVALUATION OF THEIR DC LOOP-GAIN By C. Burgio; P. Cammelli; P. Maranesi; V. Varoli	[View] [Download]
Abstract: The D.C. loop-gains of the basic PWM DC/DC converters are deduced by means of charge and energy balances and Campbell theorem. Discontinuous and continuous operation in both the Duty-Cycle Control Mode and the Current Control Mode are analyzed and complete expressions of relevant D.C. gains are given. The most peculiar results refer to the DCM/CCM transition and to some oddnesses of the Current-Control Mode.