EPE Association: EPE 2001 - Topic 08b: Measurements Techniques

EPE 2001 - Topic 08b: Measurements Techniques
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2001 - Conference > EPE 2001 - Topic 08: MEASUREMENTS AND SENSORS > EPE 2001 - Topic 08b: Measurements Techniques

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   A New Technique for Unbalanced Current and Voltage Meas. with ANN
By F. J. Alcántara; P. Salmerón; J. Prieto [View]
[Download]

Abstract: In this paper a new measurement procedure based in neural networks for the estimation of the current and voltage symmetrical components is presented. The theory foundations are the Park Vectors representation for a three-phase voltage/current. The measurement system scheme is built with three neural network blocks. The first block is a feddforward neural network that computes the Park vectors and the zero phase sequence components. The second block is an adaptative linear neuron (ADALINE) that estimates the harmonic complex coeficients of the current/voltage Park vectors. A third block is another feedforward neural network that obtains the symmetrical components of each individual voltage and current harmonic. Finally, the estimation procedure of the symmetrical components of a three-phase, unbalanced, nonlinear load current was applied to a practical case.

   A Novel Solution For Phase Current Sensing In Pwm-Vsi Based Ac Drives
By F. Parasiliti; R. Petrella; M. Tursini [View]
[Download]

Abstract: In this paper a novel solution for phase current sensing in PWM–VSI based AC drives is presented, based on a resistive sensors put in series to the lower switches of the inverter legs. It allows current sensing during each modulation cycle within the whole operating area of the inverter. Inside the overmodulation area a simple but effective modification of the modulation pattern is proposed which does not increase the complexity of the implementation almost at all. Encumbrance, complexity and cost resemble the solution using a single sensor on the DC link, but almost no operating limitations are introduced. Experimental results are presented in order to show the performance and effectiveness of the proposed method.

   A Single-Sensor Principle for Power Converters
By D. Qiu; S.Y.R. Hui; H. Chung [View]
[Download]

Abstract: A simple and effective single-sensor estimation method is described in this paper. Using only one sensor, the proposed method can provide all necessary information for feedfoward and feedback control and parameter estimation. The principle is demonstrated in a commonly used half-bridge converter under high-frequency operation. The input voltage, load resistance, load voltage and output power are estimated in this example. It is found that the proposed method can estimate these variables and parameters with high degree of accuracy. The method can reduce the number of sensors and eliminate the requirement of complex isolated feedback circuitry in power converters.

   Coil and Cable Behaviour for Rogowski Current Transducers
By W. F. Ray; C. R. Hewson [View]
[Download]

Abstract: Rogowski current transducers comprise a Rogowski coil and integrator connected by a co-axial cable. The coil and cable behave as transmission lines with different impedances and current termination presents difficulties which can result in reflexions which appear as rings on the measured waveform. This paper investigates and models the coil-cable behaviour and the integrator behaviour and compares model predictions with experimental measurements.

   DSP controlled Test Bench for Linear Actuators - Design and Choices
By P. Germano; C. Kuert; M. Jufer [View]
[Download]

Abstract: Linear motion is interesting in various applications fields such as automotive, medical or heating/ventilation/air conditioning. Linear actuators are used for flow rate regulation purposes. Knowing their characteristics and analysing their behaviour are important to improve the performances. An original DSP controlled automatic test bench has been designed and developed to characterise linear actuators, with low manual handling and enhanced measurement accuracy. The mechanical elements of the test bench consist in a load part and a test part coupled through a spring. A force sensor is placed between the load part and the spring. A linear optical encoder, fixed on the test part, directly measures the position of the test part. The measurement process takes place in two phases: first, the stress is applied on the actuator using the feed-back loop (DSP 1 in "force regulation" mode). Secondly, the actuator is started through the "DSP 2 frequency generator". The load part position is controlled according to the actuator position (DSP 1 in "position follower" mode). The absolute position and the force signals are acquired during displacement cycle. The 2 main measurement processes are based on a dichotomous method. To reach the maximal force of the actuator, the load is increased or decreased depending on the result of the previous measurement. The test bench is able to draw the following characteristic curves: force vs. current, force vs. speed, backlash/precision/stiffness/hysteresis vs. position and reverse force.

   Flow Calorimeter for Power Electronics
By A. Van Den Bossche [View]
[Download]

Abstract: A flow calorimetric system is proposed which measures the temperature rise of the air across the room of the device under test. The mass flow of the air is stabilised by controlling a fan in such way, that the temperature rise of a known dissipation is kept constant. The efficiency of power electronic converters is continuously increasing. The current and voltage waveforms contain frequencies that can disturb a wattmeter. This is in particular true for variable speed drives. The output voltage of frequency converters contains indeed slopes up to 20V/ns, which reduce the accuracy of a wattmeter. The accuracy of a wattmeter is also limited due to the fact that two similar values are subtracted. With an efficiency of 95% and a wattmeter accuracy of 1%, the accuracy for the losses is only about 40%. A calorimeter based direct loss measurement can be much more accurate. Calorimeters are mentioned as a possible method for magnetic materials [1], inductors [2], for transformers [3], as a method for measuring motor losses [4] and for general apparatus and systems [5] [6].

   High Performance Speed Measurement Method
By A. Bünte; S. Beineke; U. Schumacher [View]
[Download]

Abstract: The following is a presentation of a high performance speed measurement method, which suppresses systematic errors of encoders with sinusoidal line signals. The proposed method is based on a special transformation and a low-pass filter. Compared to state-of-the-art methods, only few additional hardware efforts are required. By means of this new scheme, dynamics and smooth running characteristics of servo drive systems are improved considerably.

   Precision low cost electric motor flux & torque measurement method
By F. Giulii Capponi; A. Stabile; A. Di Napoli; A. Violi [View]
[Download]

Abstract: Torque and flux measurements in ac motor are often a complicated matter. For flux measurement, a coil or a field sensor must be inserted inside stator windings causing relevant costs especially for big machines. Anyway, measurement has not great accuracy since calibration is not easy. For torque measurement, a telemetry system can be installed on rotor axle but, especially for notable accuracy, this system has high costs. Sometimes is not possible to install a telemetry directly on rotor axle and a gear box must be interposed, losing every chance to obtain a precise measurement. Cost and measurement uncertainties increase with machine size so that, for high power (more than 500 kW), this is about an insoluble matter. In this paper, a method based on a state observer is proposed, that overcomes all disadvantages of other methods because only voltages and current measurement is needed. For more accuracy, only rotor speed measurement is needed in addition.

   Speed measurement method for digital control system
By S. Brock; K. Zawirski [View]
[Download]

Abstract: In the paper a modified digital speed measurement method is proposed. The method has a good static accuracy, like well known other measurement procedures, but its advantage consists in a constant sampling period. The method is implemented on single chip microcontroller. Experimental results proved good properties of the proposed concept.

EPE 2001 - Topic 08b: Measurements Techniques
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2001 - Conference > EPE 2001 - Topic 08: MEASUREMENTS AND SENSORS > EPE 2001 - Topic 08b: Measurements Techniques
	[return to parent folder]

	A New Technique for Unbalanced Current and Voltage Meas. with ANN By F. J. Alcántara; P. Salmerón; J. Prieto	[View] [Download]
Abstract: In this paper a new measurement procedure based in neural networks for the estimation of the current and voltage symmetrical components is presented. The theory foundations are the Park Vectors representation for a three-phase voltage/current. The measurement system scheme is built with three neural network blocks. The first block is a feddforward neural network that computes the Park vectors and the zero phase sequence components. The second block is an adaptative linear neuron (ADALINE) that estimates the harmonic complex coeficients of the current/voltage Park vectors. A third block is another feedforward neural network that obtains the symmetrical components of each individual voltage and current harmonic. Finally, the estimation procedure of the symmetrical components of a three-phase, unbalanced, nonlinear load current was applied to a practical case.

	A Novel Solution For Phase Current Sensing In Pwm-Vsi Based Ac Drives By F. Parasiliti; R. Petrella; M. Tursini	[View] [Download]
Abstract: In this paper a novel solution for phase current sensing in PWM–VSI based AC drives is presented, based on a resistive sensors put in series to the lower switches of the inverter legs. It allows current sensing during each modulation cycle within the whole operating area of the inverter. Inside the overmodulation area a simple but effective modification of the modulation pattern is proposed which does not increase the complexity of the implementation almost at all. Encumbrance, complexity and cost resemble the solution using a single sensor on the DC link, but almost no operating limitations are introduced. Experimental results are presented in order to show the performance and effectiveness of the proposed method.

	A Single-Sensor Principle for Power Converters By D. Qiu; S.Y.R. Hui; H. Chung	[View] [Download]
Abstract: A simple and effective single-sensor estimation method is described in this paper. Using only one sensor, the proposed method can provide all necessary information for feedfoward and feedback control and parameter estimation. The principle is demonstrated in a commonly used half-bridge converter under high-frequency operation. The input voltage, load resistance, load voltage and output power are estimated in this example. It is found that the proposed method can estimate these variables and parameters with high degree of accuracy. The method can reduce the number of sensors and eliminate the requirement of complex isolated feedback circuitry in power converters.

	Coil and Cable Behaviour for Rogowski Current Transducers By W. F. Ray; C. R. Hewson	[View] [Download]
Abstract: Rogowski current transducers comprise a Rogowski coil and integrator connected by a co-axial cable. The coil and cable behave as transmission lines with different impedances and current termination presents difficulties which can result in reflexions which appear as rings on the measured waveform. This paper investigates and models the coil-cable behaviour and the integrator behaviour and compares model predictions with experimental measurements.

	DSP controlled Test Bench for Linear Actuators - Design and Choices By P. Germano; C. Kuert; M. Jufer	[View] [Download]
Abstract: Linear motion is interesting in various applications fields such as automotive, medical or heating/ventilation/air conditioning. Linear actuators are used for flow rate regulation purposes. Knowing their characteristics and analysing their behaviour are important to improve the performances. An original DSP controlled automatic test bench has been designed and developed to characterise linear actuators, with low manual handling and enhanced measurement accuracy. The mechanical elements of the test bench consist in a load part and a test part coupled through a spring. A force sensor is placed between the load part and the spring. A linear optical encoder, fixed on the test part, directly measures the position of the test part. The measurement process takes place in two phases: first, the stress is applied on the actuator using the feed-back loop (DSP 1 in "force regulation" mode). Secondly, the actuator is started through the "DSP 2 frequency generator". The load part position is controlled according to the actuator position (DSP 1 in "position follower" mode). The absolute position and the force signals are acquired during displacement cycle. The 2 main measurement processes are based on a dichotomous method. To reach the maximal force of the actuator, the load is increased or decreased depending on the result of the previous measurement. The test bench is able to draw the following characteristic curves: force vs. current, force vs. speed, backlash/precision/stiffness/hysteresis vs. position and reverse force.

	Flow Calorimeter for Power Electronics By A. Van Den Bossche	[View] [Download]
Abstract: A flow calorimetric system is proposed which measures the temperature rise of the air across the room of the device under test. The mass flow of the air is stabilised by controlling a fan in such way, that the temperature rise of a known dissipation is kept constant. The efficiency of power electronic converters is continuously increasing. The current and voltage waveforms contain frequencies that can disturb a wattmeter. This is in particular true for variable speed drives. The output voltage of frequency converters contains indeed slopes up to 20V/ns, which reduce the accuracy of a wattmeter. The accuracy of a wattmeter is also limited due to the fact that two similar values are subtracted. With an efficiency of 95% and a wattmeter accuracy of 1%, the accuracy for the losses is only about 40%. A calorimeter based direct loss measurement can be much more accurate. Calorimeters are mentioned as a possible method for magnetic materials [1], inductors [2], for transformers [3], as a method for measuring motor losses [4] and for general apparatus and systems [5] [6].

	High Performance Speed Measurement Method By A. Bünte; S. Beineke; U. Schumacher	[View] [Download]
Abstract: The following is a presentation of a high performance speed measurement method, which suppresses systematic errors of encoders with sinusoidal line signals. The proposed method is based on a special transformation and a low-pass filter. Compared to state-of-the-art methods, only few additional hardware efforts are required. By means of this new scheme, dynamics and smooth running characteristics of servo drive systems are improved considerably.

	Precision low cost electric motor flux & torque measurement method By F. Giulii Capponi; A. Stabile; A. Di Napoli; A. Violi	[View] [Download]
Abstract: Torque and flux measurements in ac motor are often a complicated matter. For flux measurement, a coil or a field sensor must be inserted inside stator windings causing relevant costs especially for big machines. Anyway, measurement has not great accuracy since calibration is not easy. For torque measurement, a telemetry system can be installed on rotor axle but, especially for notable accuracy, this system has high costs. Sometimes is not possible to install a telemetry directly on rotor axle and a gear box must be interposed, losing every chance to obtain a precise measurement. Cost and measurement uncertainties increase with machine size so that, for high power (more than 500 kW), this is about an insoluble matter. In this paper, a method based on a state observer is proposed, that overcomes all disadvantages of other methods because only voltages and current measurement is needed. For more accuracy, only rotor speed measurement is needed in addition.

	Speed measurement method for digital control system By S. Brock; K. Zawirski	[View] [Download]
Abstract: In the paper a modified digital speed measurement method is proposed. The method has a good static accuracy, like well known other measurement procedures, but its advantage consists in a constant sampling period. The method is implemented on single chip microcontroller. Experimental results proved good properties of the proposed concept.