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This paper presents a new method to diagnose rotor faults in operating three-phase induction motors under the presence of time-varying loads. The proposed diagnostic strategy relies on a combined analysis of the amplitude and phase spectra of the instantaneous active and reactive powers of the motor, and allows to discriminate the effects introduced by a rotor fault from the ones caused by an oscillating load torque, even when these phenomena occur simultaneously. A theoretical analysis carried out using a linearized model of the induction motor in a synchronous reference frame, complemented with several simulation and experimental results, confirms the validity of the proposed diagnostic approach. [ABSTRACT FROM AUTHOR]

The monitoring of power converters is critical for obtaining systems with self-diagnostic capabilities and fault-tolerant features. This paper presents an analytical work concerning the operation of matrix converters (MCs) under the presence of open-circuit faults and discusses the applicability of a method for the diagnosis of this type of failures. The proposed method uses the absolute values of nine modulated error voltages for the continuous monitoring of the condition of the bidirectional switches of an MC. This method allows a fast detection and location of the faulty switches, independent of the modulation strategy of the converter, its voltage transfer ratio, output frequency, or type of load connected to it, both in steady-state and transient regimes. The theory, validated by simulation and experimental results, demonstrates the applicability of the proposed technique for the diagnosis of faults in MCs. [ABSTRACT FROM AUTHOR]

This paper proposes the use of the multiple reference frames theory for the diagnosis of stator faults in three-phase induction motors. The development of a simplified mathematical motor model allowed the establishment of the equivalent circuits of the motor, in d-q-0 axes, in the presence of suitor interturn short circuits. The use of the stationary reference frame, clockwise and counterclockwise synchronous reference frames, allows the extraction and manipulation of the information contained in the motor supply currents in a way that the effects introduced by the fault are easily isolated and measured. A severity factor is defined and the simulation and experimental results presented demonstrate its independence in relation to the working conditions of the motor, such as the load level and unbalances in the voltage supply system. Although the technique is here introduced for the diagnosis of suitor faults, it is possible to extend its use for the diagnosis of other asymmetries such as broken rotor ban and air-gap eccentricity. [ABSTRACT FROM AUTHOR]