Andrea Andenna

Estimation of Induction Motor Operating Power Factor From Measured Current and Manufacturer Data

Three-phase induction (asynchronous) motors (IM) are industrial work-horses, making the protection of IM a very important topic. IM protection devices typically monitor the motor current and/or voltage to provide the motor protection functionalities like current overload, over/under voltage, etc. One of the interesting parameters to monitor is the operating power factor (PF) of the IM, which provides better underload protection compared to the motor current-based approaches. Traditionally, PF estimation would require both the voltage and the current measurements in order to apply the displacement method. In this paper, we present a method of determining the operating PF of the IM using only the measured current and the manufacturer data that are typically available from the nameplate and/or datasheet. Experimental results are presented to substantiate the feasibility of the proposed method, validated alongside the state of the art PF estimation methods. Operational PF can be effectively used for underload detection, like in a pump application, or PF compensation for improving the power quality.

Harmonic analysis-based diagnostics of noflow pulsation in vortex and swirl flowmeter

The vortex/swirl flowmeters are meant to measure the flowrate based on the measurement of the flow frequency. Due to the frequency-dependent computation of the flowrate, noflow pulsation causes a false positive, i.e., it indicates certain amount of flowrate when actually there is no flow. This happens when for example, the valves of the flow pipe are closed causing no flow, but some pumps are working against the closed valves to cause some pulsating pressure waves within the closed valves. The flowmeter mistakenly recognizes this as a flow and picks up the wrong frequency. This paper focuses on the diagnostic function of this particular noflow pulsation problem. Experiments, diagnostic algorithm and application results utilizing the presence of harmonics are reported in this paper.

Toward embedded broken rotor bars detection in induction machines

Low-complexity broken rotor bar detection methods amenable to an embedded implementation are dealt in this paper. A novel method based on zoom-FFT has been developed, and compared to an existing method based on zero-crossing time (ZCT) processing using real data from faulty and healthy motors. Numerical tests show that both methods can reliably detect broken rotor bars. ZCT processing entails better performance than zoom-FFT for low load and low current, but zoom-FFT is easier to tune, thus being preferable for embedded systems such as motor controllers, soft starters and drives that have to operate with a vast variety of motors.

Embedded Diagnosis for Pressure Transmitters. Automatic Detection of the Impulse Lines Plugging in Differential Pressure Transmitters (Eingebaute Diagnose für Drucksensoren. Automatische Detektion von verstopften Messleitungen bei Differenzdrucktransmittern)

The paper shows the successful implementation of the plugged-impulse-lines diagnostic function in a differential pressure transmitter. The algorithm is self-adaptive to the specific process conditions at the time of installation and proved to be applicable for both liquids and gases. Special care was taken for avoiding false alarms and having at the same time good diagnosis effectiveness. Several field tests proved the usability of the plugged-impulse-line detection function in industrial applications. Der Artikel präsentiert die erfolgreiche Implementation einer Diagnosefunktion zur Detektion von verstopften Messleitungen bei Differenzdrucktransmittern. Der Algorithmus passt sich automatisch an die spezifischen Prozessbedingungen nach der Installation an. Dabei funktioniert die Diagnose unabhängig vom Phasenzustand des Messmediums (flüssige und gasförmige Medien). Insbesondere wurde der Algorithmus so entworfen, dass im Speziellen Fehlalarme verhindert und trotzdem Verstopfungen der Messleitungen effizient diagnostiziert werden. Feldtest unter unterschiedlichen Prozessbedingungen haben eine ausgezeichnete Eignung des eingebetteten Diagnosealgorithmus für industrielle Anwendungen bewiesen.

Optimized Algorithm for Industrial Process Instrumentation Calibration based on Nonlinear Function Approximation

Calibration is an all important operation in the instrumentation industry for determining the relationship between the output(s) (or response) of a measuring instrument and the value of the input(s). Common industrial practice is to use a finite number of calibration points covering the entire calibration range. The common calibration method is to select the equidistant (over the calibration range) operating (calibration) points and performing linear interpolation operation between them. Although this ensures uniformity, but it does not guarantee effective and optimal composite modeling of the linearity and the non-linearity involved. In this paper, we propose a nonlinear function approximation-based optimized calibration technique which takes into account the composite effect of the underlying linear and nonlinear behavior of the process. Application examples are cited to substantiate the improved accuracy of the proposed algorithm over the common calibration practice.