Mariana Iorgulescu

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.

Study of three-phase bridge rectifier diagnosis based on output voltage and current analysis

The paper is indented for detection and diagnosis of three-phase bridge rectifier faults. The diagnosis is desirable in order to ensure product quality and improved operational efficiency of rectifiers as the mains power supply. The currents of three phase bridge rectifier are analyzed in order to achieve information for the detection of faults. We observe current and output voltage differences between “healthy” rectifier and rectifier without one phase or one diode for resistive load and resistive-inductive load (RL). The analysis of output voltage and current provides a method to rectifiers faults diagnosis. For diagnosing failure rectifying elements, fault detection and simulating of rectifier was presented in this paper. The output voltage and current of rectifier was comparison with simulation signals in phase to obtain the difference signals. Between simulation test and rectifier functioning, without fault and with faults, it observed any differences. The developed method is scalable to power ratings and it has been successfully demonstrated with data from three phase bridge rectifier with 1A diodes.

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.

Aspects of learning techniques in power system

This paper aims at describing the problems encountered during the learning process of the functioning of a power energy system and some solutions applied to this experience. For a better training of future electromechanical engineers, it is necessary to gain practical skills using specialized equipment during practical sessions. Using high voltage electrical equipment in the lab is not available. Therefore it is necessary to develop computer assisted learning processes. In this way students can simulate or assist maneuvers taking place in the real system. In this way, they can learn the hazards and damages that may occur as a result of wrong maneuvers. These procedures will enhance the quality of learning and teaching engineering.

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.

Continuity of Electricity Supply and Specific Indicators

The power quality in supplying the consumers is very important taking into consideration the plants’ diversity. In fact, the quality of electricity includes two components: the quality of the voltage curve—symmetrical and sinusoidal of this; quality of service—uninterrupted or interrupted short/long term. The Performance Standard imposes the quality of the distributed power in distribution service and establishes performance indicators in the provision of the distribution service, “the quality of distribution service is measured with respect to the supply continuity to the end users”. The Performance Standard sets out the performance indicators for: continuity of customers electricity supply; technical quality of distributed electricity; commercial quality of the power distribution service. The chapter aims to present an analysis of one of the components of the electricity quality, the continuity in the electricity supply of the consumers, indicating possibilities for improvement of the electricity. The indicated improvement is related to the installation of remote-controlled equipment for the rapid isolation of defects in the medium voltage network, correlated with the identification of the mounting location, which brings maximum benefits in terms of reducing the continuity indicators, especially: System Average Interruption Frequency Index (SAIFI) represents the number of customer interruptions divided by the total customers served for one year. System Average Interruption Duration Index (SAIDI) represented by the sum of customer-sustained outage minutes per year divided by the total customers served for one year. Beside the definitions of the continuity indicators, it also presents the formulas based on which they are calculated as required by the regulations in force, ways of continuously decreasing them, how to predict the targets of these indicators, both for planned interruptions and for unplanned interruptions. A case study is presented as a “self-healing” automation to isolate faults on a medium voltage line through reclosers and a General Packet Radio Service (GPRS) as a packet oriented mobile data service on the 2G/3G/4G cellular communication system’s global system for mobile communications (GSM), communication using a protocol specific to data transfer.

Study of energy efficiency in industry

This paper presents the study of energy efficiency in industry based upon information measurements, audits and technological processes. The economic operators analysed in this study are companies with primary activity in metalworking, food and bakery industry. The products of these companies belong to categories like: bread and specialities of bread, industrial scales, bearings and meat processing.