Robert Beloiu

Vibration monitoring for diagnosis of electrical equipment's faults

This paper describes diagnosis of electric faults based on vibration monitoring. Detection and diagnosis of incipient faults are desirable in order to ensure product quality and improved operational efficiency of electrical equipment running off the power supply mains. These faults could appear in any electrical equipment, but this paper focuses on the transformer, dc, three phase and single phase induction motors. In order to perform the diagnosis signals of vibration from the piezoelectric accelerometer are analyzed. This accelerometer is installed on the frame of the equipment. The Fast Fourier Transform is applied to the acquired signals. We observe significant vibration spectrum differences between “healthy” equipment and electrical equipment with faults. The high-frequency spectral analysis of vibration provides a method to detect equipment faults.

A practical approach for an introductory control engineering course

A methodology of the organization of practical classes of Control Systems course is presented in this paper. There are several voices in the community of educators and researchers over the benefits of using software simulation tools comparing the classical ones for implementing laboratory classes in engineering education curriculum. The aim of this approach is to make the students see the relation between theoretical concepts, MATLAB representations and physical circuits that can be used to implement compensators.

Study of DC motor diagnosis based on the vibration spectrum and current analysis

In this paper fault detection of permanent magnet dc motor is described. In past, Current Signature Analysis (CSA) has become an established tool for online fault analysis of AC induction motors. Presently, very little research has been performed using current signature analysis on DC motors. This paper is a brief introduction to fault diagnosis of DC motors using vibration and current signature analysis. In order to do the diagnostics there are analyzed vibration from the piezoelectric accelerometer. The accelerometer is mounted on the frames motor. Also, for the current measurement its used ampere sensor. Initially the measurements were realized by using “healthy” DC motor. Then we made successive measurements for the same type of motor with provoked faults. The many faults of DC motors are regarding collectors motor, the commutator short circuit and displaced permanent magnet out of poles in polar axe. We observe significant vibration and also current spectrum differences between “healthy” motors and faulty electrical motor. The spectral analysis of current and vibration provides a method to detect DC motors faults. Using these methods, diagnostic of commutator short circuit and displaced permanent magnet out of poles in polar axe, would be detected even if the motor operated unload.

Faults diagnosis for electrical machines based on analysis of motor current

This paper introduce faults diagnosis based on current analysis. The current spectrum of a three phases and single phase induction motor and also of a DC motor, are analyzed in order to achieve information for the detection of different faults. In order to perform the diagnosis we analyzed signals of current from the ampere sensor. The Fast Fourier Transform is applied to the signals acquired. We observe significant current spectrum differences between healthy motors and motors with faults. The high-frequency spectral analysis of current provides a method to detect bearing faults, broken rotor bars faults and commutator short circuit and presence of a displaced permanent magnet out of poles in polar axe. The system developed is scalable to different power ratings and it has been successfully tested with data from 0.75kW three phases induction motor, 0.65kW single phase induction motor and DC motor with permanent magnet.

Rotor bars diagnosis in single phase induction motors based on the vibration and current spectrum analysis

Generally, detection and diagnosis of incipient faults are desirable in order to ensure product quality and improved operational efficiency of induction motors running off the mains power supply. In this paper, the vibration and current spectrum of an induction motor are analyzed in order to achieve information for the detection of rotor bars faults. We observe significant vibration and current spectrum differences between healthy motors and motors with broken rotor bars. The high-frequency spectral analysis of vibration and current provides a method to detect broken rotor bars faults. The developed system is scalable to power ratings and it has been successfully demonstrated with data from 0.65 kW single phase induction motor.

Dynamic electronic model for a DC motor - Simulation and experimental validation

Modelling of a real system using different approaches is wide spread in the research and academic communities. There are many studies in literature that treats different ways of simulating systems more or less complex. In this paper, we developed a different approach for modelling a separate excitation DC motor. The proposed article is focused on finding a suitable model that represents the dynamic regime of such motors. Our approach uses an electronic implementation of the mathematical model of the DC motor. A special attention was given to the experimental determination of the mechanical parameters. By this approach the beneficiaries of this system, which will be engineering students, can have a better understanding on how the electronic circuits could be used to simulate a real system. Also our approach could serve for implementing remote laboratories for systems modelling-simulation for electrical engineering studies.

Noise and vibration monitoring for diagnosis of DC motor's faults

This paper describes faults detection and diagnosis of permanent magnet dc electric motors based on noise and vibration monitoring. Detection and diagnosis of incipient faults are desirable in order to ensure product quality and improved operational efficiency of electrical equipment and to avoid the power off from supply mains. In order to do the diagnosis there are analyzed noises from the microphones and vibration from the piezoelectric accelerometer. The microphones are installed around of the frame of the equipment and the accelerometer is mounted on the frames motor. The Fast Fourier Transform is applied to the acquired signals. We observe significant noise and vibration spectrum differences between “healthy” motors and faults electrical motor. The high-frequency spectral analysis of noise and vibration provides a method to detect motors faults.

Real-time strategy to optimize the fuel flow rate of fuel cell hybrid power source under variable load cycle

A real-time optimization (RTO) strategy for the Fuel Cell Hybrid Power Sources (FCHPS) is proposed in this paper. The optimization strategy is based on the Global Extremum Seeking (GES) search of the optimal value of the fuel flow rate of the FC stack. The airflow rate is controlled by the FC current as in the Static Feed-Forward (sFF) RTO strategy, where both fueling flow rates are controlled by the FC current. The performance of the proposed Fuel_GES-RTO strategy is shown in comparison with the sFF-RTO strategy for constant and variable load. In the last case, a Load-Following (LF) control of the boost converter is used for both strategies.

Electrical Power Systems

The general description of architecture and classification of power systems are presented at the beginning of the first chapter. Afterwards the basic concepts and analysis methods of electrical power systems are given, being accompanied by many examples of calculation. Also the power flow between the generators and consumers has been considered. In order to characterize the parameters of power systems next section of the first chapter is dedicated to measurement methods of power systems parameters. Electrical energy needed to power industrial or household electric consumers, like any other product, should satisfy specific quality requirements. In this respect the power quality aspects and the standards for power systems parameters are presented. The flow of reactive power and energy in power systems produces significant effects on the optimal functioning of suppliers and customers which are connected. Therefore in the last section of first chapter is defined the importance of reactive power in AC power systems and on its various understandings. Usually the first chapter is closed with a large list of bibliographic references.

Hands-on solutions for teaching basic introductory control systems course

The Control Systems course is taught in educational electric engineering programs all over the world. The method used for teaching this course is mainly by mathematical representation and software simulation of systems behavior. In this work the author presents a different approach, which is based on making hands-on experimental applications. The solution presented in this article is based on decomposing and re-arranging the transfer function representation of a dynamic system in order to implement it using electronic circuits. Combining the presented method with a popular simulation software leads to the implementation of practical and effective laboratory classes for this course.