A. J. Marques Cardoso

Rotor Cage Fault Diagnosis in Three-Phase Induction Motors by Extended Park's Vector Approach

This paper introduces a new approach, based on the spectral analysis of the motor current Parks Vector modulus, for detecting the occurrence of rotor cage faults in operating three-phase induction machines. The major theoretical principles of the Extended Parks Vector Approach are described. Both simulation and laboratory test results demonstrate how the presence of rotor cage faults can be effectively detected by the application of this new approach. These results are also correlated with the ones obtained by the conventional motor current spectral analysis and by the classic Parks Vector Approach.This paper introduces a new approach, based on the spectral analysis of the motor current Parks Vector modulus, for detecting the occurrence of rotor cage faults in operating three-phase induction machines. The major theoretical principles of the Extended Parks Vector Approach are described. Both simulation and laboratory test results demonstrate how the presence of rotor cage faults can be effectively detected by the application of this new approach. These results are also correlated with the ones obtained by the conventional motor current spectral analysis and by the classic Parks Vector Approach.

Rotor cage fault diagnosis in three-phase induction motors, by Park's vector approach

The subject of on-line detection of rotor cage faults in three-phase induction motors is discussed, and a noninvasive approach, based on computer-aided monitoring of the stator current Parks vector, is introduced, Both simulation and laboratory test results demonstrate the effectiveness of the proposed technique, for detecting broken rotor bars or end-rings in operating three-phase induction machines. On-site tests conducted in a power plant, using the diagnostic instrumentation system developed, are also reported.

Voltage source inverter fault diagnosis in variable speed AC drives, by the average current Park's vector approach

This paper introduces a new approach, based on the average motor supply current Parks vector monitoring, for diagnosing voltage source inverter faults in variable speed AC drives. Both simulation and laboratory tests results demonstrate the effectiveness of the proposed on-line diagnostic technique.

A Permeance-Based Transformer Model and Its Application to Winding Interturn Arcing Fault Studies

This paper investigates the behavior of power transformers under the occurrence of permanent or intermittent winding insulation faults. For the study of these phenomena, a simple and efficient permeance-based electromagnetic transformer model is proposed, which is based on the simultaneous consideration of magnetic and electric equivalent circuits. To incorporate the internal faults in this model, a suitable equivalent circuit of the faulty winding is described. With the aid of this transformer model, the onload exciting current Parks Vector Approach will be applied for diagnosing the occurrence of permanent and intermittent winding faults. Experimental and simulation tests results are presented in this paper, which demonstrate not only the adequacy of the digital transformer model for winding fault studies, but also the effectiveness of the proposed technique for detecting winding interturn insulation faults in operating three-phase transformers.

A new approach for real-time multiple open-circuit fault diagnosis in voltage source inverters

Practically all the diagnostic methods for open-circuit faults in voltage source inverters (VSI) developed during the last decades, are focused on the occurrence of single faults and do not have the capability to handle and identify multiple failures. This paper presents a new method for real-time diagnostics of multiple open-circuit faults in voltage source inverters feeding ac machines. In contrast with the majority of the methods found in the literature which are based on the motor phase currents average values, the average absolute values are used here as principal quantities in order to formulate the diagnostic variables. These prove to be more robust against the issue of false alarms, carrying also information about multiple open-circuit failures. Furthermore, by the combination of these variables with the machine phase currents average values, it is possible to obtain characteristic signatures, which allow for the detection and identification of single and multiple open-circuit faults.

Fault diagnosis on a pwm rectifier ac drive system with fault tolerance using the average current Park's Vector approach

Motor drives reliability is becoming a fundamental aspect of their general performance due to the widespread use of motor-drive systems in numerous critical applications. Therefore, strategies able to operate under faulty conditions are of extreme importance. However, for them to operate there is the obvious need of detecting, identifying and locating the fault.

Thermal Performance of a Three-Phase Induction Motor Under Fault Tolerant Operating Strategies

This paper presents the thermal behavior of a three-phase induction motor under direct torque control, when supplied by a three-phase voltage source inverter with fault tolerant capabilities. For this purpose, a fault tolerant operating strategy based on the connection of the faulty inverter leg to the dc link middle point was considered. The motor thermal profile is obtained through the use of nine thermocouples positioned in both stator and rotor circuits. The experimental results obtained under fault compensated operation show that, as far as the motor thermal characteristics are concerned, it is not necessary to reinforce the motor insulation properties since it is already prepared for such an operation.

Experimental study of the effect of positive sequence voltage on the derating of induction motors under voltage unbalance

This paper presents the results of an experimental study on derating of an induction motor under different voltage unbalanced conditions and its comparison with the NEMA standard MG1 voltage unbalance derating graph. During the derating tests the 4 kW squirrel cage induction motor temperature rise was kept constant at the rated value and the windings temperature was measured on-line by means of an accurate digital thermal monitoring system with nine thermocouples positioned in both stator and rotor circuits. The obtained results show that the positive sequence voltage plays an important role in the derating performance of the induction motor under unbalanced conditions, and that the unbalance voltage indices currently used do not allow for accurately measuring this influence.

An Experimental Technique for Estimating the ESR and Reactance Intrinsic Values of Aluminum Electrolytic Capacitors

This paper presents an experimental technique that allows the determination of the reactance and ESR intrinsic values of aluminum electrolytic capacitors. The equivalent circuit of an electrolytic capacitor comprises an equivalent series inductance (ESL), an equivalent series resistance (ESR) and a capacitance (C), whose values change with frequency. Therefore, the behavior of an electrolytic capacitor varies from approximately a simple capacitor for low frequencies, to a resistor at its resonance frequency, and finally to an inductor for frequencies higher than its resonance frequency. The knowledge of the resonance frequency of the electrolytic capacitors, as well as their equivalent circuit at the operating frequency becomes of paramount importance for designing purposes. The ESR is one of the most critical problems of static converters that operate near the resonance frequency of the electrolytic capacitors. An increased ESR value leads to a significant increase in the alternate component of the output voltage, requiring a constant action of the control system. To validate the proposed technique and to demonstrate its applicability some experimental and simulated results are presented

Converters fault-diagnosis in PMSG drives for wind turbine applications

In order to compensate the worldwide energy consumption that is still rising, the wind energy is becoming more and more important. For this reason, the analysis of wind energy conversion systems, in which the occurrence of faults has a high negative impact, becomes a very important issue. Considering this, the aim of this paper is to present some diagnostic methods for open-circuit faults in the two power converters of a permanent magnet synchronous generator (PMSG) drive for wind turbine applications. To achieve this goal, fault analysis is the first step, in order to know which parameters can be used for the diagnosis. The following step is the development of reliable diagnostic methods. Various simulation results, considering multiple faults in the grid-side converter and a single fault in the PMSG-side converter, are presented.