EPE Association: EPE 2009 - Subtopic 18-2 - DS: 'Operating Quality of Systems'

EPE 2009 - Subtopic 18-2 - DS: 'Operating Quality of Systems'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 18: 'Operating Quality of Systems' > EPE 2009 - Subtopic 18-2 - DS: 'Operating Quality of Systems'

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   Air-Cored Common Mode Filter with Integrated Capacitors
By Mikko KUISMA, Valentin DZHANKHOTOV, Pertti SILVENTOINEN, Juha PYRHONEN [View]
[Download]

Abstract: Common Mode (CM) electromagnetic interference in power lines are typically reduced with a CM filter, which consists of discrete capacitors and inductors. An air-cored EMI filter with CM choke and integrated X and Y capacitors utilizing the parasitic capacitance of the windings is proposed. Its benefits include better high frequency performance, reduced component count, and improved manufacturability. Experimental results are provided.

   Bearing Diagnosis Methodologies by means of Common Mode Current
By Miguel DELGADO [View]
[Download]

Abstract: The most bearings diagnosis methodologies has been designed typically by means of vibration analysis, but a numerous studies in the last years are focused in non-invasive techniques Motor Current Signature Analysis (MCSA) based. This paper shows two different methodologies for bearings diagnosis over induction motors by means of the stator Common Mode Current (CMC). It is acquired directly the CMC from the source that inverter provide to the motor. The first analysis is performed directly over a temporal acquisition of stator CMC. The second analysis is based in the spectral analysis of a single CMC discharge. It is shown also the development of a CMC probe, which corresponds to the tool used to check the first methodology. Finally, it is presented a vibration analysis over the same induction motors in order to confirm the bearings diagnosis extracted from the previous methodologies CMC based.

   Change of Terminal Characteristics of a Voltage-Source-Inverter (VSI) due to Semiconductor Device Degradation
By DAWEI XIANG, Shaoyong YANG, Li RAN, Peter TAVNER, Angus BRYANT, Phil MAWBY [View]
[Download]

Abstract: In this paper, physics-based IGBT and diode models are used to simulate two 3-phase VSI systems using different power modules in SABER. The device parameters for two standard SEMIKRON power modules, the 1200V/75A single chip module and the 1200V/300A multi-chip module, are extracted following parameterization procedure. The effects of three typical degradations are considered, including solder fatigue, gate aging and sub-chip loss resulting from bond wire lift-off, which have different impacts on the device internal parameters and external characteristics. Device parameters, e.g. Rth ,Vth and chip active area are changed correspondingly in the simulation to represent the aging effects and a series of simulation runs are performed for an inverter system. Four aspects of converter terminal characteristics are investigated to identify any measurable signature used for condition monitoring (CM): the module case temperature, the output current harmonics, the phase-leg resistance and the dv/dt values associated with the rising and falling edges of the PWM output voltage. Theoretical analyses backed by simulation results are presented regarding the possibility of a practical CM scheme.

   Characterization of IGBT Devices for Use in Series Resonant Inverter for Induction Heating Applications
By Jose JORDÃN, Cesar CASES, Jose Miguel MAGRANER, Vicente ESTEVE, Esteban SANCHIS, Enrique MASET, Enrique DEDE, Eva GUMBAU [View]
[Download]

Abstract: This paper aims to determine the maximum frequency achievable in a 25 kW series inverter for induction heating applications and to compare, in hard switching conditions, four fast transistors IGBTs 600A and 1200V modules encapsulated in 62mm from different suppliers. The comparison has been done at 25 and 125ÂºC in a set-up. Important differences between modules have been obtained depending on the die temperature.

   Closed Loop Temperature and Repetition Rate Control for Accelerated Pulse Stress Testing of Smart Power Switches
By Hans-Peter KREUTER, Michael GLAVANOVICS, Christoph SCHREIBER [View]
[Download]

Abstract: Cyclic stress tests for smart power switches require a significant effort in test resources, particularly in test time, to provide statistically valid life time data. To address this issue we present a novel accelerated pulse stress test method to speed up the qualification process of smart power switches. A closed loop repetition rate controller employing individual temperature sensors stabilizes device operating points while preserving standardized test conditions. Temperature acquisition module and controller are implemented on a PXI-based system hosting a PC and an FPGA device. Finally the method is experimentally verified and lifetime data are compared to standard open loop test results.

   Common-Mode Choke Coils Characterization
By Konstantin KOSTOV, Jorma KYYRÃ„ [View]
[Download]

Abstract: Common-mode (CM) chokes are four-terminal devices with different CM and differential-mode (DM) characteristics. The paper reviews the models for two- and four-terminal inductors and presents two methods to obtain the CM and DM characteristics of four-terminal devices. More specifically, it shows how the insertion loss and π-equivalent circuits of a CM choke can be obtained using two- and four-port network parameters. However, these characterization methods are applicable not only to CM chokes, but to any four-terminal component or network, such as single-phase power filters. The results show that second order linear circuit models cannot describe accurately the CM and DM characteristics of a CM choke over a wide frequency range. For the studied example, the DM charac-teristics were more complex than the CM ones.

   Complementary MOS structures for common mode EMI reduction
By MANH HUNG TRAN, Jean Christophe CREBIER [View]
[Download]

Abstract: The paper deals with the management and the reduction of conducted common mode EMI noise in power converters. Especially, it is presented how complementary P-N MOSFET structures, used in a specific manner, are able of great and natural common mode current reductions. The advantages obtained by the use of complementary MOSFET topologies are balanced with the additional conduction losses that P MOSFETs are responsible of. The paper presents these issues based on simulation and practical results.

   EMI/EMC troubleshooting techniques in switching mode power supplies
By ARTURO MEDIANO [View]
[Download]

Abstract: This work is intended to describe the origin of EMI from a state of the art flyback power supply and to explain some experimental techniques with current and near field probes useful to pass EMC regulations, to optimize a design or, simply, to better understand the culprits of the problem. The dialogue (poster) session in EPE09 is appropiated to show the technique in a practical way to delegates interested in the subject and this document is a general description of that session.

   Extended Reliability of Substrate Solder Joints in Power Modules
By DOMENICO BARONE, THOMAS HUNGER, REINHOLD BAYERER [View]
[Download]

Abstract: The life time of the solder joint between base plate and ceramic substrate is usually tested by passively heating and cooling the power module (thermal cycling). This provokes delamination in the solder layer. But, the silicon dies in the power module are actively heated in the application. The accelerated life time test simulating this load is power cycling. The modules commonly fail at the end of their life due to bond wire fatigue or cracks in the solder layer between the dies and the substrate. The paper studies the behavior of the substrate solder layer under power cycling conditions with respect to its passive thermal cycling capability. The high number of power cycles is utilized to evaluate the solder life time at low temperature swings. The method proposed is applied to modules with copper base plate and substrate solder containing lead. A comparison with simulation results confirms the applicability of the method. Improved manufacturing technology allows for an increased thermal cycling capability of modules with lead free substrate solder and copper base plates. Experimental results on the thermal cycling capability of modules with AlSiC base plates and lead free substrate solder are presented.

   Fault Anticipation Software System Architecture for Aircraft EMA
By Miguel DELGADO [View]
[Download]

Abstract: This paper shows a Fault Anticipation Software System (FASS) architecture, for diagnosis and prognosis purposes, in order to be implemented in a FASS unit, that nowadays, is a necessary tool to diagnose aircraft Electro Mechanical Actuators which are been implemented in order to face up to â€œMore Electric Aircraftâ€ (MEA) technologies. This work shows the requirements in a FAS system, and a fault diagnosis and prognosis structure purposed to solve this challenge.

   Performance Evaluation of Frequencial Behavior of Layout (PCB + Parts) of the Electronic Ballasts to Fluorescent Lighting in the Electromagnetic Interference (E
By Paulo RANGEL, Adriano RIES, Adroaldo RAIZER, James ROUDET [View]
[Download]

Abstract: This article presents a study about the non-ideal and frequency dependent behavior of the set which constitutes the layout, that is, the Printed Circuit Board (PCB) linked to electro-electronic components in electronic ballasts for fluorescent lighting, related to the conducted disturbance at mains terminals (electromagnetic interference - EMI). The determination and experimental proof of PCB and some specific components non-ideal models are made and the results applied in order to obtain an answer concerning the EMI through a computational simulation. The results are discussed and compared with the EMI measurements and tests in an implemented prototype in a lab.

   POWER MANAGEMENT IN MULTI-SOURCE MULTI-LOAD ENERGY HARVESTING SYSTEMS
By Stefano SAGGINI, Paolo MATTAVELLI [View]
[Download]

Abstract: The forthcoming scenario of the wireless sensor network and the so called Pervasive Computing would greatly boost if all electronic systems involved in their deployment could feature some sort of energy self-sufficiency. In this application an aggressive power management solution is required in order to collect a sufficient amount of energy in storage elements in general from different power sources. This paper is focused on the development of the power supply systems, in particular on switching converters for energy harvesting applications. Its main goal is the development of high efficiency conversion systems, featuring the minimum number of conversion stages and of magnetic components, and the optimization of the power management. In particular the paper is focused on multi-input/multi-output dc-dc converters, enabling the connection of one or more sources of energy (solar, vibrational, RF, etc.), of some energy accumulation devices (micro-batteries, capacitors, supercapacitors), and several loads (microcontroller, transmitter, sensors, etc.). The modulation techniques and the power management are also discussed, to comply with multi-source/multi-load conditions.

   Prediction of the EMC behaviour of switch mode power supplies in boundary conduction mode including switching frequency limitations
By Daniel KUEBRICH, Thomas DUERBAUM [View]
[Download]

Abstract: The conducted EMC behavior of a single phase PFC converter operating in boundary conduction mode is predicted by an analytical simulation process. The simulation routines are very flexible in use allowing also for simulation of switching frequency limitations, valley switching and valley skipping. The straight forward simulation process for differential mode disturbances including all blocks of the EMC measurement equipment is described in detail. The benefit of this approach is that it can be adapted to every converter type. In this paper it has been applied to predict the differential mode disturbance level of a PFC boost converter operating in boundary conduction mode. The simulated disturbance levels are compared with results of an EMC measurement on a sample PFC converter. Furthermore, the impact of switching frequency limitations on the differential mode EMI behavior is discussed.

   Sensorless pump operation estimation
By Tero AHONEN, Jussi TAMMINEN, Jero AHOLA, Juha KESTILÃ„ [View]
[Download]

Abstract: Pumps are widely used in industrial applications, and they account for nearly a quarter of the electric energy consumption in the European industry. Pumps are often overdimensioned or they may be driven inefficiently, which causes unnecessary energy costs. If the pump drive is not equipped with appropriate measurements, inefficient pump operation may remain undetected for years and lead to a premature pump failure that also has an increasing effect on the pump driveâ€™s life cycle costs. Hence, pump operation monitoring may give a possibility for notable cost savings even if the pump is driven with a frequency converter. Since modern frequency converters provide estimates on the motor operation, they are a natural choice to monitor also the pump operation. In this paper, model-based estimation methods for the pump operating point are presented. Estimation methods are based on the internal measurements of the frequency converter, and therefore, external measurements are not necessary. Hence, the methods are a simple and cost-effective alternative to analyze pump operation: they can be applied in the control, optimization, and auditing purposes of a variable-speed-driven pump. Theoretical background is given for the methods, and they are evaluated with laboratory tests. According to the test measurements, estimation methods are applicable in auditing purposes.

   Short-Circuit Critical Frequency for Induction Heating Parallel Resonant Inverters
By Jose JORDÃN, Jose Miguel MAGRANER, Cesar CASES, Vicente ESTEVE, Enrique DEDE, Esteban SANCHIS-KILDERS, Enrique MASET, Eva GUMBAU [View]
[Download]

Abstract: In induction heating applications, the component being heated is very close to the heating coil. Due to the high temperatures reached during the process, isolation is not always possible and short-circuits may happen. Two main types of short-circuit should be considered: complete inductor's short-circuit and short-circuit between windings. Parallel resonant oscillators are widely used in induction heating applications together with a current fed inverter to generate the alternating current. Parasitic inductance in the connection between the inverter and the oscillator tank may generate high over-voltages if the switching is uncontrolled. The aim of the paper is to describe the protections needed to avoid the failure of the transistors due to over-voltages which may occur during the short-circuit process. Short-circuit critical frequency is calculated and determines whether over-voltages will appear after short-circuit occurs.

   Virtual Machine - A Hardware in the Loop Test for Drive Inverters
By Till BOLLER, Ralph KENNEL [View]
[Download]

Abstract: This paper presents a new approach for hardware in the loop testing of voltage source inverters for drive applications. For this purpose the inverter is not connected to a real machine, but to a second power inverter instead, which acts like an electrical machine. Thereby the inverter under test can operate in its normal mode, which in the most of the cases is a field oriented current control with superimposed speed controller.

EPE 2009 - Subtopic 18-2 - DS: 'Operating Quality of Systems'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 18: 'Operating Quality of Systems' > EPE 2009 - Subtopic 18-2 - DS: 'Operating Quality of Systems'
	[return to parent folder]

	Air-Cored Common Mode Filter with Integrated Capacitors By Mikko KUISMA, Valentin DZHANKHOTOV, Pertti SILVENTOINEN, Juha PYRHONEN	[View] [Download]
Abstract: Common Mode (CM) electromagnetic interference in power lines are typically reduced with a CM filter, which consists of discrete capacitors and inductors. An air-cored EMI filter with CM choke and integrated X and Y capacitors utilizing the parasitic capacitance of the windings is proposed. Its benefits include better high frequency performance, reduced component count, and improved manufacturability. Experimental results are provided.

	Bearing Diagnosis Methodologies by means of Common Mode Current By Miguel DELGADO	[View] [Download]
Abstract: The most bearings diagnosis methodologies has been designed typically by means of vibration analysis, but a numerous studies in the last years are focused in non-invasive techniques Motor Current Signature Analysis (MCSA) based. This paper shows two different methodologies for bearings diagnosis over induction motors by means of the stator Common Mode Current (CMC). It is acquired directly the CMC from the source that inverter provide to the motor. The first analysis is performed directly over a temporal acquisition of stator CMC. The second analysis is based in the spectral analysis of a single CMC discharge. It is shown also the development of a CMC probe, which corresponds to the tool used to check the first methodology. Finally, it is presented a vibration analysis over the same induction motors in order to confirm the bearings diagnosis extracted from the previous methodologies CMC based.

	Change of Terminal Characteristics of a Voltage-Source-Inverter (VSI) due to Semiconductor Device Degradation By DAWEI XIANG, Shaoyong YANG, Li RAN, Peter TAVNER, Angus BRYANT, Phil MAWBY	[View] [Download]
Abstract: In this paper, physics-based IGBT and diode models are used to simulate two 3-phase VSI systems using different power modules in SABER. The device parameters for two standard SEMIKRON power modules, the 1200V/75A single chip module and the 1200V/300A multi-chip module, are extracted following parameterization procedure. The effects of three typical degradations are considered, including solder fatigue, gate aging and sub-chip loss resulting from bond wire lift-off, which have different impacts on the device internal parameters and external characteristics. Device parameters, e.g. Rth ,Vth and chip active area are changed correspondingly in the simulation to represent the aging effects and a series of simulation runs are performed for an inverter system. Four aspects of converter terminal characteristics are investigated to identify any measurable signature used for condition monitoring (CM): the module case temperature, the output current harmonics, the phase-leg resistance and the dv/dt values associated with the rising and falling edges of the PWM output voltage. Theoretical analyses backed by simulation results are presented regarding the possibility of a practical CM scheme.

	Characterization of IGBT Devices for Use in Series Resonant Inverter for Induction Heating Applications By Jose JORDÃN, Cesar CASES, Jose Miguel MAGRANER, Vicente ESTEVE, Esteban SANCHIS, Enrique MASET, Enrique DEDE, Eva GUMBAU	[View] [Download]
Abstract: This paper aims to determine the maximum frequency achievable in a 25 kW series inverter for induction heating applications and to compare, in hard switching conditions, four fast transistors IGBTs 600A and 1200V modules encapsulated in 62mm from different suppliers. The comparison has been done at 25 and 125ÂºC in a set-up. Important differences between modules have been obtained depending on the die temperature.

	Closed Loop Temperature and Repetition Rate Control for Accelerated Pulse Stress Testing of Smart Power Switches By Hans-Peter KREUTER, Michael GLAVANOVICS, Christoph SCHREIBER	[View] [Download]
Abstract: Cyclic stress tests for smart power switches require a significant effort in test resources, particularly in test time, to provide statistically valid life time data. To address this issue we present a novel accelerated pulse stress test method to speed up the qualification process of smart power switches. A closed loop repetition rate controller employing individual temperature sensors stabilizes device operating points while preserving standardized test conditions. Temperature acquisition module and controller are implemented on a PXI-based system hosting a PC and an FPGA device. Finally the method is experimentally verified and lifetime data are compared to standard open loop test results.

	Common-Mode Choke Coils Characterization By Konstantin KOSTOV, Jorma KYYRÃ„	[View] [Download]
Abstract: Common-mode (CM) chokes are four-terminal devices with different CM and differential-mode (DM) characteristics. The paper reviews the models for two- and four-terminal inductors and presents two methods to obtain the CM and DM characteristics of four-terminal devices. More specifically, it shows how the insertion loss and π-equivalent circuits of a CM choke can be obtained using two- and four-port network parameters. However, these characterization methods are applicable not only to CM chokes, but to any four-terminal component or network, such as single-phase power filters. The results show that second order linear circuit models cannot describe accurately the CM and DM characteristics of a CM choke over a wide frequency range. For the studied example, the DM charac-teristics were more complex than the CM ones.

	Complementary MOS structures for common mode EMI reduction By MANH HUNG TRAN, Jean Christophe CREBIER	[View] [Download]
Abstract: The paper deals with the management and the reduction of conducted common mode EMI noise in power converters. Especially, it is presented how complementary P-N MOSFET structures, used in a specific manner, are able of great and natural common mode current reductions. The advantages obtained by the use of complementary MOSFET topologies are balanced with the additional conduction losses that P MOSFETs are responsible of. The paper presents these issues based on simulation and practical results.

	EMI/EMC troubleshooting techniques in switching mode power supplies By ARTURO MEDIANO	[View] [Download]
Abstract: This work is intended to describe the origin of EMI from a state of the art flyback power supply and to explain some experimental techniques with current and near field probes useful to pass EMC regulations, to optimize a design or, simply, to better understand the culprits of the problem. The dialogue (poster) session in EPE09 is appropiated to show the technique in a practical way to delegates interested in the subject and this document is a general description of that session.

	Extended Reliability of Substrate Solder Joints in Power Modules By DOMENICO BARONE, THOMAS HUNGER, REINHOLD BAYERER	[View] [Download]
Abstract: The life time of the solder joint between base plate and ceramic substrate is usually tested by passively heating and cooling the power module (thermal cycling). This provokes delamination in the solder layer. But, the silicon dies in the power module are actively heated in the application. The accelerated life time test simulating this load is power cycling. The modules commonly fail at the end of their life due to bond wire fatigue or cracks in the solder layer between the dies and the substrate. The paper studies the behavior of the substrate solder layer under power cycling conditions with respect to its passive thermal cycling capability. The high number of power cycles is utilized to evaluate the solder life time at low temperature swings. The method proposed is applied to modules with copper base plate and substrate solder containing lead. A comparison with simulation results confirms the applicability of the method. Improved manufacturing technology allows for an increased thermal cycling capability of modules with lead free substrate solder and copper base plates. Experimental results on the thermal cycling capability of modules with AlSiC base plates and lead free substrate solder are presented.

	Fault Anticipation Software System Architecture for Aircraft EMA By Miguel DELGADO	[View] [Download]
Abstract: This paper shows a Fault Anticipation Software System (FASS) architecture, for diagnosis and prognosis purposes, in order to be implemented in a FASS unit, that nowadays, is a necessary tool to diagnose aircraft Electro Mechanical Actuators which are been implemented in order to face up to â€œMore Electric Aircraftâ€ (MEA) technologies. This work shows the requirements in a FAS system, and a fault diagnosis and prognosis structure purposed to solve this challenge.

	Performance Evaluation of Frequencial Behavior of Layout (PCB + Parts) of the Electronic Ballasts to Fluorescent Lighting in the Electromagnetic Interference (E By Paulo RANGEL, Adriano RIES, Adroaldo RAIZER, James ROUDET	[View] [Download]
Abstract: This article presents a study about the non-ideal and frequency dependent behavior of the set which constitutes the layout, that is, the Printed Circuit Board (PCB) linked to electro-electronic components in electronic ballasts for fluorescent lighting, related to the conducted disturbance at mains terminals (electromagnetic interference - EMI). The determination and experimental proof of PCB and some specific components non-ideal models are made and the results applied in order to obtain an answer concerning the EMI through a computational simulation. The results are discussed and compared with the EMI measurements and tests in an implemented prototype in a lab.

	POWER MANAGEMENT IN MULTI-SOURCE MULTI-LOAD ENERGY HARVESTING SYSTEMS By Stefano SAGGINI, Paolo MATTAVELLI	[View] [Download]
Abstract: The forthcoming scenario of the wireless sensor network and the so called Pervasive Computing would greatly boost if all electronic systems involved in their deployment could feature some sort of energy self-sufficiency. In this application an aggressive power management solution is required in order to collect a sufficient amount of energy in storage elements in general from different power sources. This paper is focused on the development of the power supply systems, in particular on switching converters for energy harvesting applications. Its main goal is the development of high efficiency conversion systems, featuring the minimum number of conversion stages and of magnetic components, and the optimization of the power management. In particular the paper is focused on multi-input/multi-output dc-dc converters, enabling the connection of one or more sources of energy (solar, vibrational, RF, etc.), of some energy accumulation devices (micro-batteries, capacitors, supercapacitors), and several loads (microcontroller, transmitter, sensors, etc.). The modulation techniques and the power management are also discussed, to comply with multi-source/multi-load conditions.

	Prediction of the EMC behaviour of switch mode power supplies in boundary conduction mode including switching frequency limitations By Daniel KUEBRICH, Thomas DUERBAUM	[View] [Download]
Abstract: The conducted EMC behavior of a single phase PFC converter operating in boundary conduction mode is predicted by an analytical simulation process. The simulation routines are very flexible in use allowing also for simulation of switching frequency limitations, valley switching and valley skipping. The straight forward simulation process for differential mode disturbances including all blocks of the EMC measurement equipment is described in detail. The benefit of this approach is that it can be adapted to every converter type. In this paper it has been applied to predict the differential mode disturbance level of a PFC boost converter operating in boundary conduction mode. The simulated disturbance levels are compared with results of an EMC measurement on a sample PFC converter. Furthermore, the impact of switching frequency limitations on the differential mode EMI behavior is discussed.

	Sensorless pump operation estimation By Tero AHONEN, Jussi TAMMINEN, Jero AHOLA, Juha KESTILÃ„	[View] [Download]
Abstract: Pumps are widely used in industrial applications, and they account for nearly a quarter of the electric energy consumption in the European industry. Pumps are often overdimensioned or they may be driven inefficiently, which causes unnecessary energy costs. If the pump drive is not equipped with appropriate measurements, inefficient pump operation may remain undetected for years and lead to a premature pump failure that also has an increasing effect on the pump driveâ€™s life cycle costs. Hence, pump operation monitoring may give a possibility for notable cost savings even if the pump is driven with a frequency converter. Since modern frequency converters provide estimates on the motor operation, they are a natural choice to monitor also the pump operation. In this paper, model-based estimation methods for the pump operating point are presented. Estimation methods are based on the internal measurements of the frequency converter, and therefore, external measurements are not necessary. Hence, the methods are a simple and cost-effective alternative to analyze pump operation: they can be applied in the control, optimization, and auditing purposes of a variable-speed-driven pump. Theoretical background is given for the methods, and they are evaluated with laboratory tests. According to the test measurements, estimation methods are applicable in auditing purposes.

	Short-Circuit Critical Frequency for Induction Heating Parallel Resonant Inverters By Jose JORDÃN, Jose Miguel MAGRANER, Cesar CASES, Vicente ESTEVE, Enrique DEDE, Esteban SANCHIS-KILDERS, Enrique MASET, Eva GUMBAU	[View] [Download]
Abstract: In induction heating applications, the component being heated is very close to the heating coil. Due to the high temperatures reached during the process, isolation is not always possible and short-circuits may happen. Two main types of short-circuit should be considered: complete inductor's short-circuit and short-circuit between windings. Parallel resonant oscillators are widely used in induction heating applications together with a current fed inverter to generate the alternating current. Parasitic inductance in the connection between the inverter and the oscillator tank may generate high over-voltages if the switching is uncontrolled. The aim of the paper is to describe the protections needed to avoid the failure of the transistors due to over-voltages which may occur during the short-circuit process. Short-circuit critical frequency is calculated and determines whether over-voltages will appear after short-circuit occurs.

	Virtual Machine - A Hardware in the Loop Test for Drive Inverters By Till BOLLER, Ralph KENNEL	[View] [Download]
Abstract: This paper presents a new approach for hardware in the loop testing of voltage source inverters for drive applications. For this purpose the inverter is not connected to a real machine, but to a second power inverter instead, which acts like an electrical machine. Thereby the inverter under test can operate in its normal mode, which in the most of the cases is a field oriented current control with superimposed speed controller.