G.A. Capolino

A frequency-domain detection of stator winding faults in induction machines using an external flux sensor

The aim of this paper is to present the advantage of stator fault detection using an external flux sensor in working induction machine. In the past twenty years, axial flux sensors have been used for diagnosis purpose but rarely in presence of complex power supply such as voltage static inverter. In this paper, it is proved that a simple external flux sensor is more efficient than the classical stator current analysis to detect intern-turn short circuit in three-phase induction machine. The new result is that, even in presence of power supply harmonics, it is possible to detect easily the stator winding faults in the low frequency range of the flux spectrum with low frequency resolution.

Trends in Fault Diagnosis for Electrical Machines: A Review of Diagnostic Techniques

The fault diagnosis of rotating electrical machines has received an intense amount of research interest during the last 30 years. Reducing maintenance costs and preventing unscheduled downtimes, which result in losses of production and financial incomes, are the priorities of electrical drives manufacturers and operators. In fact, both correct diagnosis and early detection of incipient faults lead to fast unscheduled maintenance and short downtime for the process under consideration. They also prevent the harmful and sometimes devastating consequences of faults and failures. This topic has become far more attractive and critical as the population of electric machines has greatly increased in recent years. The total number of operating electrical machines in the world was around 16.1 billion in 2011, with a growth rate of about 50% in the last five years [1].

An equivalent internal circuit of the induction machine for advanced spectral analysis

The aim of this paper is to develop a method to validate an equivalent internal circuit of the three-phase squirrel-cage induction machine for advanced signal processing including fault diagnosis. The proposed method is based on the computation of the stator and rotor current spectra. An experimental setup for an 11-kW induction machine was developed in order to get numerical data for voltages and currents from the stator side. The comparison between the analytical computation, the simulation, and the experimental results, shows the model capability to reproduce the electromagnetic phenomena in the induction machine with mixed time and space harmonics. The proposed model can be used to design electrical fault detection devices with low cost and noninvasive sensors.

Diagnosis of broken-bars fault in induction machines using higher order spectral analysis.

Detection and identification of induction machine faults through the stator current signal using higher order spectra analysis is presented. This technique is known as motor current signature analysis (MCSA). This paper proposes two higher order spectra techniques, namely the power spectrum and the slices of bi-spectrum used for the analysis of induction machine stator current leading to the detection of electrical failures within the rotor cage. The method has been tested by using both healthy and broken rotor bars cases for an 18.5 kW-220 V/380 V-50 Hz-2 pair of poles induction motor under different load conditions. Experimental signals have been analyzed highlighting that bi-spectrum results show their superiority in the accurate detection of rotor broken bars. Even when the induction machine is rotating at a low level of shaft load (no-load condition), the rotor fault detection is efficient. We will also demonstrate through the analysis and experimental verification, that our proposed proposed-method has better detection performance in terms of receiver operation characteristics (ROC) curves and precision-recall graph.

Trends in Electrical Machines Control: Samples for Classical, Sensorless, and Fault-Tolerant Techniques

This article has given a significant number of examples of contemporary control techniques for EDs. Of course, many more special machines or specific applications can be investigated as well. However, with IMs, PMSMs, SRMs, and hydrogenerators, the most current industrial applications have been addressed. Most of the presented techniques are not yet fully used in industry and are still under evaluation before diffusion at a large scale in the industry. Therefore, many control techniques, such as FTC schemes, are still under investigation for industrial applications with reliability requirements. Even if there are no standard schemes to implement these modern control techniques, it has been commonly admitted that sensorless and fault-tolerant structures will be used more and more in the future and that they are fully implementable on low-cost digital platforms with a high degree of integration.

Analytical approach of the stator current frequency harmonics computation for detection of induction machine rotor faults

The aim of this paper is to analyze theoretically and experimentally the stator current of a three-phase squirrel cage induction machine in order to show how it is influenced by rotor faults. The approach used for this study analyzes the modification introduced by n broken rotor bars in the rotor cage magnetomotive force (MMF) and then, estimates the resulting frequency spectrum in the stator current. This approach is validated in a 3 kW-230 V/400 V-50 Hz-2850 rpm-2 poles three-phase induction machine, showing the sensible frequency components to this fault condition.

Diagnostic Technique based on Rotor Modulating Signals Signature Analysis for Doubly Fed Induction Machines in Wind Generator Systems

The paper introduces an advanced monitoring and diagnosis system for the detection of incipient electrical faults in doubly fed induction generators (DFIGs) used in wind generator systems. In this application the rotor power is supplied by a converter for the control of active and reactive power flow from the generator to the mains. The paper deals with a new diagnostic method based on the analysis of the rotor modulating signals. Simulation and experimental results confirm that the analysis of the spectra of rotor input modulating signals leads to an effective diagnostic procedure. The system is suitable to be easily embedded in the drive control system

Simulation of a doubly-fed induction machine for wind turbine generator fault analysis

For modern large wind farms, it is more and more interesting to design an efficient diagnostics system oriented to wind turbine generators based on doubly-fed induction machine (DFIM). In this paper, a complete system will be analyzed by suitable simulations to deeply study fault influence and to identify the best diagnostic procedure to perform predictive maintenance. All the research efforts have been developed on different signature analysis (XSA) in order to detect or to predict electrical and mechanical faults in wound-rotor induction machines. They will be applied on wind turbine generators and their effectiveness will be studied.

Improvement of frequency resolution for three-phase induction machine fault diagnosis

This paper deals with the use of the zoom FFT algorithm (ZFFTA) for the electrical fault diagnosis of squirrel-cage three-phase induction machines with a special interest in broken rotor bar situation. The machine stator current can be analysed to observe the side-band harmonics around the fundamental frequency. In this case, it is necessary to take a very long data sequence to get high frequency resolution. This is not always possible due to the hardware and software limitations. The proposed algorithm can be considered for solving high frequency resolution problem without increasing the initial data acquisition size. The ZFFTA is applied to detect incipient rotor fault in a three-phase squirrel-cage induction machine by using both stator current and stray flux sensors.

Torque Ripples Suppression for Six-Phase Induction Motors Under Open Phase Faults

This paper introduces a new disturbance free operation method for six-phase induction motors. The machine is supposed to loss one or more phases and to have a pulsating torque. In order to improve the motor torque, we propose a new control law satisfying a condition required to have a smooth torque. The simulation and experimental results illustrate the validity and the efficiency of the proposed method for disturbance free operation of six-phase induction machines