EPE Association: EPE 1991 - 29 - Session 3.7: ESTIMATION, MEASUREMENTS AND PROTECTIONS

EPE 1991 - 29 - Session 3.7: ESTIMATION, MEASUREMENTS AND PROTECTIONS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - Conference > EPE 1991 - 29 - Session 3.7: ESTIMATION, MEASUREMENTS AND PROTECTIONS

   [return to parent folder]

   COMBINED OVERCURRENT AND OVERTEMPERATURE PROTECTION WITH SENSEFETS
By W. G. Dunford; G. Liu [View]
[Download]

Abstract: The application of a rugged protection circuit in an FET-based photovoltaic powered inverter drive is described. The circuit is based on the charactetistics of the International Rectifier HEXSense FET and does not require any direct current or temperature input. A simple switching arrangement is used to vary the resistance connected to the FET sense terminals. With a high resistance the sense voltage is effectively the voltage across the temperature dependent channel resistance of the FET. A small external resistance swamps the effect of the channel resistance and develops a voltage which is primarily a function of the channel current. A comparison of the two voltages allows the device temperature to be estimated.

   INDUCTION MOTOR PARAMETER ESTIMATION USING ON-LINE SPECTRAL ANALYSIS
By P. P. Acarnley; H. Chai; D. J. Atkinson [View]
[Download]

Abstract: A computationally economic on-line parameter estimation algorithm for the induction motor is described in this paper . It is shown that, by using spectral analysis, it is possible to design on-line test methods which resemble the standard off-line no-load and locked-rotor tests. The motor parameters are derived from those signal components most relevant to the parameters being calculated, and therefore it is possible to achieve conciseness and stability in the algorithm. The paper presents the results of experimental tests carried out on a 2kW induction motor.

   CAPACITIVE ANGULAR TRANSDUCER FOR TOOTHED AIR GAP STEPPING MOTORS
By V. Trifa; A. Broscoi [View]
[Download]

Abstract: The paper deals with a new electronic method and device for detecting the rotor angular position of the stepping motors with toothed structure of their air gap. The method refers to fitting special capacitors inside the stater slots, whose capacitance varies with the rotor angle. The device contains two capacitive bridges that provide amplitude-modulated output signals, which can be used for yielding either analogical, or incremental information about the rotor movement. Two types of capacitors are studied by an approximate calculus and their performances are indicated. Then the electronic part of the transducer is described and an application to the closed-loop control of a variable-reluctance stepping motor is given. Finally, the advantages and a few practical considerations over capacitive transducer are presented.

   METHOD FOR THE ESTIMATION OF ROTOR RESISTANCE IN INDUCTION MOTORS
By D. J. Atkinson; P. P. Acarnley; J. W. Finch [View]
[Download]

Abstract: The problem of rotor resistance estimation is central to self-tuning of indirect vector control drives. The vector controlled drive is normally chosen for applications of high dynamic performance, therefore estimation in both transient and steady state is important. This paper examines the use of an extended Kalman Filter to the non-linear estimation of rotor resistance. The extended Kalman Filter is known to be computationally intensive and therefore a new reduced order algorithm is presented. Both simulation and experimental results are included for trials on a 3kW induction motor.

   ELIMINATING THE HARMONICS FROM MEASURED CURRENT VALUES IN PWM DRIVES
By F. Bauer; G. Heinle [View]
[Download]

Abstract: ln electric drive systems the stator currents and voltages are measured for control purposes. PWM inverter operation inherently produces harmonic voltages and currents along with the desired fundamental frequency. These harmonics cause harmonic components in the measured signal. The consequences are: distortion in the reference voltages, lower permissible amplification of the current regulators with a resulting impairment of dynamic behaviour and a limited stability range for the control system. For high drive system performance, stator quantities are needed which are devoid of inverter-induced harmonics. A method is introduced that eliminates such harmonics from the measured signal. lt enables the harmonic-free measuring of currents and voltages synchronously and non-synchronously with the pulse patterns. This proposed correction method enables to obtain suitable mean values of fundamental-frequency quantities for all three phases to serve further processing purposes. The method can be implemented bath on-line or off-line and can be employed for either two-level or three-level inverters.

   COMPARISON OF MAGNETIC NOISE DUE TO OUTPUT WAVEFORM HARMONICS OF VARIOUS VOLTAGE SOURCE INVERTERS
By S. Iida; Y. Okuma; S. Masukawa; S. Miyairi; B. K. Bose [View]
[Download]

Abstract: Harmonic components in the output waveform of an inverter cause magnetic noise to the loads, such as motors or transformers. In this paper, we discuss quantitatively the noise by several voltage source inverters. By applying the equivalent noise voltage to estimate the relationship between the magnetic noise and the harmonics, we can predict in advance that the noise by multi-pulse inverter changes widely by pulse number of the output waveform, and then the noise by multi-step inverter can be reduced in comparison with multi-pulse inverter. We can show the validity of our predictions by experimental results of the magnetic noise caused from the load transformer. And then, we investigate also the noise generated from the output transformers to construct the output voltages in the double connected inverters. We try to reduce the total noise added from the load and the output transformers by applying connection with a output transformer only.

   APPLICATION OF NEW MEASUREMENT TECHNIQUES TO PWM WAVEFORMS
By G. Andria; L. Salvatore; M. Savino; A. Trotta [View]
[Download]

Abstract: The PWM modulation techniques, suitably employed in a.c. variable-speed drive systems, cause high levels of harmonic distortion in the waveforms of voltage and current. On the other hand, the PWM voltage waveforms exhibit large-band frequency spectra, with a slow decay of the magnitudes of harmonic components. In the paper, new DSP techniques are proposed, which allow the user to perform highly accurate measurements. A multistage decimation of the acquired data may be performed by non-recursive realization of low-pass digital filters, to achieve a frequency-zooming in fast Fourier transform (FFT) spectrum analysis. Optimized cosine windows have been designed to realize low-pass FIR filters with maximally flat amplitude response in passband. Both pass- and stopband ripple are even lower than those attained by using classical equiripple Parks-McClellan and Kaiser-window design techniques. To select the frequency-band to be analyzed with high resolution a digital multiplier is required for frequency shifting. In order to minimize the negative effects of spectral leakage caused by an asynchronous sampling, new flat-top windows have been designed and characterized, which offer negligible errors in this kind of measurements. An important advantage of these windows consists in the increase of computational speed, because of the uselessness of interpolation algorithms, otherwise necessary.

   DETERMINING STRUCTURAL IMPEDANCES
By W. A. Cronje; J. A. Ferreira; J. D. van Wyk [View]
[Download]

Abstract: Structural (stray/parasitic) impedances need to be quantified in order to include them in circuit simulations. Different techniques for determining structural impedances are investigated and compared with regard to accuracy and ease of use. The investigation is conducted for a structural configuration, bus-bar go heat sink return conductor, that find typical application as an interconnection in converter circuitry. The investigation is conducted for relatively high frequencies 100kHz-4MHz and non-infinite earth plane. The impedances for the structure are calculated for several frequencies in the band of interest using the finite element technique as well as with an analytical method derived from microstrip theory. The calculated inductance and resistance as functions of frequency are compared to get an indication of the relative accuracy of the techniques. Simulation results of the dynamic circuit behaviour is compared with experimental results on a simple chopper circuit.

   EQUIPMENT FOR STATIC PROTECTION 100 A RMS 660 V RMS
By J. F. De Palma; J. J. Rousseau; J. P. Chante; P. Epron; R. Deshayes [View]
[Download]

Abstract: The low voltage electromechanical circuit breakers have attained a certain maturity over the last few years. The requirements of the end user are new and correspond to very precise needs: ideal breaking capability with overvoltage control, better discrimination, absence of wear and maintenance and possibility to predetermine performance of the equipment for protection. The association of the fuse, the electromechanical circuit breaker and the thermal relay necessary to cover all bands of protection tor the equipment, between the initial instant and continuous running, has no langer to take place with static protection devices. The intrinsic qualities of control and rapidity of the power semiconductor make it used more and more as the breaking medium in the perfecting of new static protection devices. In this article the authors present the breaking medium for a static protection device with a high breaking capacity (greater than 50 kA). The original choice retains from the time of conception of the static limiting device, some nominal characteristics, 660 volts, 100 amperes, presented and justified. The solution retained consists of putting in parallel some bidirectional static switching modules characterized by a commutable current of 100 A.

   SINGLE PHASE SUPPLY IMPEDANCE: ITS MEASUREMENT AND INFLUENCE ON NON-LINEAR (RECTIFIER) LOADS
By Rex M. Davis; Alan R. Jewell [View]
[Download]

Abstract: The impedance of single phase supplies plays an important part in determining the severity of harmonic currents drawn by non-linear loads and the consequent voltage disturbances experienced by other users. At present most electronic power supplies still use a diode bridge rectifier connected to the 220V/240V ac supply via simple line filter, and to a large electrolytic smoothing capacitor on the dc side. This arrangement produces high peak value, short duration current pulses giving rise to many harmonics. lt shows how supply impedance can be simply measured. The use of passive components to reduce harmonic currents is discussed, based upon computer simulated results. These enable comparisons to be made with more sophisticated active methods for power factor improvement, based on the modulation of a boost converter to create a sinusoidal envelope for the high frequency current ripple.

   THE USE OF ROGOWSKI COILS FOR CURRENT WAVEFORM MEASUREMENT IN POWER ELECTRONIC CIRCUITS
By W. F. Ray; K. D. Murray [View]
[Download]

Abstract: A Rogowski coil is an air cored solenoidal winding of small cross section which can be looped around a conductor carrying a current i. A voltage is induced in the coil proportioned to di/dt. This voltage may be integrated to reproduce the current waveform. A fast integrator is required with a limited low frequency gain to reduce drift effects. The paper describes the design and construction of a Rogowski coil and integrator for measuring current waveforms up to 2500A peak containing fast transients and therefore suitable for power electronic circuit development. Problems associated with connecting the coil to the integrator are discussed and oscilloscope waveforms shown and compared with those from a coaxial shunt.

   NEW METHOD OF PHASE MEASUREMENT BASED ON INCREMENT METHOD OF FREQUENCY MEASUREMENT
By S. Kapka [View]
[Download]

Abstract: The paper presents a new method of phase measuring based on frequency measurement method. The operation principle and basic formulae for determining phase and frequency are given. Dynamic and static accuracy of the measurement has been discussed. The proposed method applies two measurement Iines, each one having a marker at the beginning of frequency-function measurement cycle. lf the markers occur synchronously then the measurement of frequency and phase is possible. lf they occur asynchronously it is possible to measure the frequency-function of the markers. When the values of the frequency are obtained it is possible to determine the slip value. The operation identification in the terms "synchronous", "asynchronous'', has been done basing on the following criteria: equality of frequency and phase for the measuring range greater than 2pi. The possible applicatlons of the method are the measurements of actual values of: frequency-function, phase, and the quotient of the frequencies.

   THE EXPERIMENTAL INVESTIGATION OF MULTI-PARAMETER IDENTIFICATION METHODS FOR CAGE INDUCTION MOTORS
By M. Sumner; G. M. Asher [View]
[Download]

Abstract: Two new schemes for the on-line calculation of both the rotor time constant and the magnetising inductance of a vector controlled induction motor are presented. Both rely only on the premeasured values of stator resistance and total leakage inductance measured at start up, and allow the user to assess the operation of the drive for various flux / torque levels. These schemes have been devised as part of a self-commissioning package for an induction motor drive, but can also be used as background adaption techniques for a fully commissioned drive. The accuracy of the schemes is verified by measurements of the airgap flux using sensing coils mounted within the machine, and by comparison with the 'Reactive Power' method of identification.

   NEW FORMALISM OF A CONTROL AUTOMATON FOR SYNCHRONOUS AND INDUCTION MACHINES FED BY A PWM INVERTER
By E. Monmasson; J. C. Hapiot; M. Grandpierre; X. Roboam [View]
[Download]

Abstract: The on-line implementation of highly sophisticated control laws for variable-speed drives often lead to a capacity overflow of the used microprocessors. Although the use of a control automaton in order to take over a part of the microprocessor tasks is not a new technique, but the fact is that these circuits which employed TTL logic devices were cumbersome and were fixed within a determinated structure. Because of their high degree of integrability and the possibility of software reconfiguration, the LCA (Logic Cell Array) revive the interest in the study of this structure. For this reason, we propose throughout this study, a completely revised organisation of a control automaton of a speed drive for synchronous or asynchronous motors fed by a PWM voltage inverter. The behaviour of the automaton is analysed by means of simulation.

   DIGITAL MEASUREMENT PROCEDURES IN A MICROPROCESSOR-BASED EXCITATION SYSTEM
By G. Corbetta; G. Ottaviani [View]
[Download]

Abstract: In a microprocessor-based excitation system the measurement of electrical variables, like current, voltage, frequency, active and reactive power, is obtained by mean of a real-time measuring system. In order to obtain the values of all variables necessary to control the excitation, proper computation are made over the samples of the input signals given by current and voltage transformers. Main characteristics to qualify such measuring system are accuracy and speed of both acquisition and computation technics, together with response time and mains frequency and harmonics rejection. To realize our generator excitation system, and its measuring section, general purpose VME boards have been chosen.

   MEASUREMENT SYSTEM WITH MICROPROCESSOR IN ELECTRIC NETWORKS
By N. Messina; G. Salzano [View]
[Download]

Abstract: The actual knowledge on digital electronic technology allows the realization of devices that have performances these can allow the inclusive management of complex and large systems, as an electric distribution or transport network at various levels of voltage. The present paper considers the project of a measurement system that is found on elaboration, trough microprocessor, of signals these are proportional at the electrical greatness voltage, current and phase, to obtain values of the active and reactive power and the corresponding values of the energy at the aim of the technical and commercial management of the electric power system. The designed device allows to calculate instantaneous values of active and reactive electric power and to integrate them by means of right software registered in a EPROM who are as well memorized also source users and contractual conditions codes and ethers subroutines that can manage suitable data which identify the state of network object of management. Obtained values are utilized to bring up to date to a EEPROM, with a cycle suitably, picked out from designer, that gives the digital data at a visualization system and, if occur, at a possible transmission system. That transmission can be start trough suitable codified signals that can get to device trough metallic or optic support or trough radio-link system. The possibility to utilize the same electric distribution network as support for the transmission of the signals that manage the device and at same time for the data generated of the same device, presents great technical and economical interest. The control apparatus of the system is a 8 bit NMOS microprocessor, that processes digital signals which are picked up from the network trough an input-output interface. Results are accumulated in a RAM to be transferred with cyclical procedure in the EEPROM. The measurement described system allows also to manage the users from the commercial point of view, computing the absorbed active and reactive electric power also in function of various contractual conditions (seasonal or time rates, etc.) and transmitting the data at the centres of commercial affairs. Trough appropriate interface it is possible to operate appropriate devices for activate or inactivate the users or for change limits of allowed absorbed electric power of users.

   COMPUTER AIDED ANALYSIS AND DESIGN OF POWER ELECTRONIC CIRCUITS WITH PECAN (POST-PROCESSING)
By H. A. Kojori; H. Jin; J. D. Lavers [View]
[Download]

Abstract: The paper discusses the theory and implementation of a general purpose Post-Processing analysis stage that is being integrated in the Power Electronic Circuit ANalysis package (PECAN) to automatically i) obtain waveform Fourier analysis, ii) perform frequency response analysis, and finally iii) select and rate components of power electronic circuits and systems by running an optimization program is discussed. This technique is based on a black box representation of the controlled system and no prior knowledge about the system performance is required. Time varying systems and / or nonlinear systems can be easily handled. By using an optimization program, the optimum values / ratings of the different components of the system are automatically obtained. Therefore, the user avoids tedious iterative simulations (often manually performed). By simulating the actual controlled system, the open-loop frequency response is predicted which leads to a more systematic design of the system in a much faster and safer fashion. Several examples have been presented to illustrate the attractive features and capabilities of the post-processing analysis stage.

EPE 1991 - 29 - Session 3.7: ESTIMATION, MEASUREMENTS AND PROTECTIONS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - Conference > EPE 1991 - 29 - Session 3.7: ESTIMATION, MEASUREMENTS AND PROTECTIONS
	[return to parent folder]

	COMBINED OVERCURRENT AND OVERTEMPERATURE PROTECTION WITH SENSEFETS By W. G. Dunford; G. Liu	[View] [Download]
Abstract: The application of a rugged protection circuit in an FET-based photovoltaic powered inverter drive is described. The circuit is based on the charactetistics of the International Rectifier HEXSense FET and does not require any direct current or temperature input. A simple switching arrangement is used to vary the resistance connected to the FET sense terminals. With a high resistance the sense voltage is effectively the voltage across the temperature dependent channel resistance of the FET. A small external resistance swamps the effect of the channel resistance and develops a voltage which is primarily a function of the channel current. A comparison of the two voltages allows the device temperature to be estimated.

	INDUCTION MOTOR PARAMETER ESTIMATION USING ON-LINE SPECTRAL ANALYSIS By P. P. Acarnley; H. Chai; D. J. Atkinson	[View] [Download]
Abstract: A computationally economic on-line parameter estimation algorithm for the induction motor is described in this paper . It is shown that, by using spectral analysis, it is possible to design on-line test methods which resemble the standard off-line no-load and locked-rotor tests. The motor parameters are derived from those signal components most relevant to the parameters being calculated, and therefore it is possible to achieve conciseness and stability in the algorithm. The paper presents the results of experimental tests carried out on a 2kW induction motor.

	CAPACITIVE ANGULAR TRANSDUCER FOR TOOTHED AIR GAP STEPPING MOTORS By V. Trifa; A. Broscoi	[View] [Download]
Abstract: The paper deals with a new electronic method and device for detecting the rotor angular position of the stepping motors with toothed structure of their air gap. The method refers to fitting special capacitors inside the stater slots, whose capacitance varies with the rotor angle. The device contains two capacitive bridges that provide amplitude-modulated output signals, which can be used for yielding either analogical, or incremental information about the rotor movement. Two types of capacitors are studied by an approximate calculus and their performances are indicated. Then the electronic part of the transducer is described and an application to the closed-loop control of a variable-reluctance stepping motor is given. Finally, the advantages and a few practical considerations over capacitive transducer are presented.

	METHOD FOR THE ESTIMATION OF ROTOR RESISTANCE IN INDUCTION MOTORS By D. J. Atkinson; P. P. Acarnley; J. W. Finch	[View] [Download]
Abstract: The problem of rotor resistance estimation is central to self-tuning of indirect vector control drives. The vector controlled drive is normally chosen for applications of high dynamic performance, therefore estimation in both transient and steady state is important. This paper examines the use of an extended Kalman Filter to the non-linear estimation of rotor resistance. The extended Kalman Filter is known to be computationally intensive and therefore a new reduced order algorithm is presented. Both simulation and experimental results are included for trials on a 3kW induction motor.

	ELIMINATING THE HARMONICS FROM MEASURED CURRENT VALUES IN PWM DRIVES By F. Bauer; G. Heinle	[View] [Download]
Abstract: ln electric drive systems the stator currents and voltages are measured for control purposes. PWM inverter operation inherently produces harmonic voltages and currents along with the desired fundamental frequency. These harmonics cause harmonic components in the measured signal. The consequences are: distortion in the reference voltages, lower permissible amplification of the current regulators with a resulting impairment of dynamic behaviour and a limited stability range for the control system. For high drive system performance, stator quantities are needed which are devoid of inverter-induced harmonics. A method is introduced that eliminates such harmonics from the measured signal. lt enables the harmonic-free measuring of currents and voltages synchronously and non-synchronously with the pulse patterns. This proposed correction method enables to obtain suitable mean values of fundamental-frequency quantities for all three phases to serve further processing purposes. The method can be implemented bath on-line or off-line and can be employed for either two-level or three-level inverters.

	COMPARISON OF MAGNETIC NOISE DUE TO OUTPUT WAVEFORM HARMONICS OF VARIOUS VOLTAGE SOURCE INVERTERS By S. Iida; Y. Okuma; S. Masukawa; S. Miyairi; B. K. Bose	[View] [Download]
Abstract: Harmonic components in the output waveform of an inverter cause magnetic noise to the loads, such as motors or transformers. In this paper, we discuss quantitatively the noise by several voltage source inverters. By applying the equivalent noise voltage to estimate the relationship between the magnetic noise and the harmonics, we can predict in advance that the noise by multi-pulse inverter changes widely by pulse number of the output waveform, and then the noise by multi-step inverter can be reduced in comparison with multi-pulse inverter. We can show the validity of our predictions by experimental results of the magnetic noise caused from the load transformer. And then, we investigate also the noise generated from the output transformers to construct the output voltages in the double connected inverters. We try to reduce the total noise added from the load and the output transformers by applying connection with a output transformer only.

	APPLICATION OF NEW MEASUREMENT TECHNIQUES TO PWM WAVEFORMS By G. Andria; L. Salvatore; M. Savino; A. Trotta	[View] [Download]
Abstract: The PWM modulation techniques, suitably employed in a.c. variable-speed drive systems, cause high levels of harmonic distortion in the waveforms of voltage and current. On the other hand, the PWM voltage waveforms exhibit large-band frequency spectra, with a slow decay of the magnitudes of harmonic components. In the paper, new DSP techniques are proposed, which allow the user to perform highly accurate measurements. A multistage decimation of the acquired data may be performed by non-recursive realization of low-pass digital filters, to achieve a frequency-zooming in fast Fourier transform (FFT) spectrum analysis. Optimized cosine windows have been designed to realize low-pass FIR filters with maximally flat amplitude response in passband. Both pass- and stopband ripple are even lower than those attained by using classical equiripple Parks-McClellan and Kaiser-window design techniques. To select the frequency-band to be analyzed with high resolution a digital multiplier is required for frequency shifting. In order to minimize the negative effects of spectral leakage caused by an asynchronous sampling, new flat-top windows have been designed and characterized, which offer negligible errors in this kind of measurements. An important advantage of these windows consists in the increase of computational speed, because of the uselessness of interpolation algorithms, otherwise necessary.

	DETERMINING STRUCTURAL IMPEDANCES By W. A. Cronje; J. A. Ferreira; J. D. van Wyk	[View] [Download]
Abstract: Structural (stray/parasitic) impedances need to be quantified in order to include them in circuit simulations. Different techniques for determining structural impedances are investigated and compared with regard to accuracy and ease of use. The investigation is conducted for a structural configuration, bus-bar go heat sink return conductor, that find typical application as an interconnection in converter circuitry. The investigation is conducted for relatively high frequencies 100kHz-4MHz and non-infinite earth plane. The impedances for the structure are calculated for several frequencies in the band of interest using the finite element technique as well as with an analytical method derived from microstrip theory. The calculated inductance and resistance as functions of frequency are compared to get an indication of the relative accuracy of the techniques. Simulation results of the dynamic circuit behaviour is compared with experimental results on a simple chopper circuit.

	EQUIPMENT FOR STATIC PROTECTION 100 A RMS 660 V RMS By J. F. De Palma; J. J. Rousseau; J. P. Chante; P. Epron; R. Deshayes	[View] [Download]
Abstract: The low voltage electromechanical circuit breakers have attained a certain maturity over the last few years. The requirements of the end user are new and correspond to very precise needs: ideal breaking capability with overvoltage control, better discrimination, absence of wear and maintenance and possibility to predetermine performance of the equipment for protection. The association of the fuse, the electromechanical circuit breaker and the thermal relay necessary to cover all bands of protection tor the equipment, between the initial instant and continuous running, has no langer to take place with static protection devices. The intrinsic qualities of control and rapidity of the power semiconductor make it used more and more as the breaking medium in the perfecting of new static protection devices. In this article the authors present the breaking medium for a static protection device with a high breaking capacity (greater than 50 kA). The original choice retains from the time of conception of the static limiting device, some nominal characteristics, 660 volts, 100 amperes, presented and justified. The solution retained consists of putting in parallel some bidirectional static switching modules characterized by a commutable current of 100 A.

	SINGLE PHASE SUPPLY IMPEDANCE: ITS MEASUREMENT AND INFLUENCE ON NON-LINEAR (RECTIFIER) LOADS By Rex M. Davis; Alan R. Jewell	[View] [Download]
Abstract: The impedance of single phase supplies plays an important part in determining the severity of harmonic currents drawn by non-linear loads and the consequent voltage disturbances experienced by other users. At present most electronic power supplies still use a diode bridge rectifier connected to the 220V/240V ac supply via simple line filter, and to a large electrolytic smoothing capacitor on the dc side. This arrangement produces high peak value, short duration current pulses giving rise to many harmonics. lt shows how supply impedance can be simply measured. The use of passive components to reduce harmonic currents is discussed, based upon computer simulated results. These enable comparisons to be made with more sophisticated active methods for power factor improvement, based on the modulation of a boost converter to create a sinusoidal envelope for the high frequency current ripple.

	THE USE OF ROGOWSKI COILS FOR CURRENT WAVEFORM MEASUREMENT IN POWER ELECTRONIC CIRCUITS By W. F. Ray; K. D. Murray	[View] [Download]
Abstract: A Rogowski coil is an air cored solenoidal winding of small cross section which can be looped around a conductor carrying a current i. A voltage is induced in the coil proportioned to di/dt. This voltage may be integrated to reproduce the current waveform. A fast integrator is required with a limited low frequency gain to reduce drift effects. The paper describes the design and construction of a Rogowski coil and integrator for measuring current waveforms up to 2500A peak containing fast transients and therefore suitable for power electronic circuit development. Problems associated with connecting the coil to the integrator are discussed and oscilloscope waveforms shown and compared with those from a coaxial shunt.

	NEW METHOD OF PHASE MEASUREMENT BASED ON INCREMENT METHOD OF FREQUENCY MEASUREMENT By S. Kapka	[View] [Download]
Abstract: The paper presents a new method of phase measuring based on frequency measurement method. The operation principle and basic formulae for determining phase and frequency are given. Dynamic and static accuracy of the measurement has been discussed. The proposed method applies two measurement Iines, each one having a marker at the beginning of frequency-function measurement cycle. lf the markers occur synchronously then the measurement of frequency and phase is possible. lf they occur asynchronously it is possible to measure the frequency-function of the markers. When the values of the frequency are obtained it is possible to determine the slip value. The operation identification in the terms "synchronous", "asynchronous'', has been done basing on the following criteria: equality of frequency and phase for the measuring range greater than 2pi. The possible applicatlons of the method are the measurements of actual values of: frequency-function, phase, and the quotient of the frequencies.

	THE EXPERIMENTAL INVESTIGATION OF MULTI-PARAMETER IDENTIFICATION METHODS FOR CAGE INDUCTION MOTORS By M. Sumner; G. M. Asher	[View] [Download]
Abstract: Two new schemes for the on-line calculation of both the rotor time constant and the magnetising inductance of a vector controlled induction motor are presented. Both rely only on the premeasured values of stator resistance and total leakage inductance measured at start up, and allow the user to assess the operation of the drive for various flux / torque levels. These schemes have been devised as part of a self-commissioning package for an induction motor drive, but can also be used as background adaption techniques for a fully commissioned drive. The accuracy of the schemes is verified by measurements of the airgap flux using sensing coils mounted within the machine, and by comparison with the 'Reactive Power' method of identification.

	NEW FORMALISM OF A CONTROL AUTOMATON FOR SYNCHRONOUS AND INDUCTION MACHINES FED BY A PWM INVERTER By E. Monmasson; J. C. Hapiot; M. Grandpierre; X. Roboam	[View] [Download]
Abstract: The on-line implementation of highly sophisticated control laws for variable-speed drives often lead to a capacity overflow of the used microprocessors. Although the use of a control automaton in order to take over a part of the microprocessor tasks is not a new technique, but the fact is that these circuits which employed TTL logic devices were cumbersome and were fixed within a determinated structure. Because of their high degree of integrability and the possibility of software reconfiguration, the LCA (Logic Cell Array) revive the interest in the study of this structure. For this reason, we propose throughout this study, a completely revised organisation of a control automaton of a speed drive for synchronous or asynchronous motors fed by a PWM voltage inverter. The behaviour of the automaton is analysed by means of simulation.

	DIGITAL MEASUREMENT PROCEDURES IN A MICROPROCESSOR-BASED EXCITATION SYSTEM By G. Corbetta; G. Ottaviani	[View] [Download]
Abstract: In a microprocessor-based excitation system the measurement of electrical variables, like current, voltage, frequency, active and reactive power, is obtained by mean of a real-time measuring system. In order to obtain the values of all variables necessary to control the excitation, proper computation are made over the samples of the input signals given by current and voltage transformers. Main characteristics to qualify such measuring system are accuracy and speed of both acquisition and computation technics, together with response time and mains frequency and harmonics rejection. To realize our generator excitation system, and its measuring section, general purpose VME boards have been chosen.

	MEASUREMENT SYSTEM WITH MICROPROCESSOR IN ELECTRIC NETWORKS By N. Messina; G. Salzano	[View] [Download]
Abstract: The actual knowledge on digital electronic technology allows the realization of devices that have performances these can allow the inclusive management of complex and large systems, as an electric distribution or transport network at various levels of voltage. The present paper considers the project of a measurement system that is found on elaboration, trough microprocessor, of signals these are proportional at the electrical greatness voltage, current and phase, to obtain values of the active and reactive power and the corresponding values of the energy at the aim of the technical and commercial management of the electric power system. The designed device allows to calculate instantaneous values of active and reactive electric power and to integrate them by means of right software registered in a EPROM who are as well memorized also source users and contractual conditions codes and ethers subroutines that can manage suitable data which identify the state of network object of management. Obtained values are utilized to bring up to date to a EEPROM, with a cycle suitably, picked out from designer, that gives the digital data at a visualization system and, if occur, at a possible transmission system. That transmission can be start trough suitable codified signals that can get to device trough metallic or optic support or trough radio-link system. The possibility to utilize the same electric distribution network as support for the transmission of the signals that manage the device and at same time for the data generated of the same device, presents great technical and economical interest. The control apparatus of the system is a 8 bit NMOS microprocessor, that processes digital signals which are picked up from the network trough an input-output interface. Results are accumulated in a RAM to be transferred with cyclical procedure in the EEPROM. The measurement described system allows also to manage the users from the commercial point of view, computing the absorbed active and reactive electric power also in function of various contractual conditions (seasonal or time rates, etc.) and transmitting the data at the centres of commercial affairs. Trough appropriate interface it is possible to operate appropriate devices for activate or inactivate the users or for change limits of allowed absorbed electric power of users.

	COMPUTER AIDED ANALYSIS AND DESIGN OF POWER ELECTRONIC CIRCUITS WITH PECAN (POST-PROCESSING) By H. A. Kojori; H. Jin; J. D. Lavers	[View] [Download]
Abstract: The paper discusses the theory and implementation of a general purpose Post-Processing analysis stage that is being integrated in the Power Electronic Circuit ANalysis package (PECAN) to automatically i) obtain waveform Fourier analysis, ii) perform frequency response analysis, and finally iii) select and rate components of power electronic circuits and systems by running an optimization program is discussed. This technique is based on a black box representation of the controlled system and no prior knowledge about the system performance is required. Time varying systems and / or nonlinear systems can be easily handled. By using an optimization program, the optimum values / ratings of the different components of the system are automatically obtained. Therefore, the user avoids tedious iterative simulations (often manually performed). By simulating the actual controlled system, the open-loop frequency response is predicted which leads to a more systematic design of the system in a much faster and safer fashion. Several examples have been presented to illustrate the attractive features and capabilities of the post-processing analysis stage.