Rolling bearing faults are generally slowly progressive; therefore the development of an effective diagnostic technique could be worth to detect such faults in their incipient phase and to prevent complete failure of the motor. The methods proposed in the literature for this purpose are mainly based on measuring and analyzing the vibration and current. Here, a novel technique based on the stray flux measurement in different positions around the electrical machine is proposed. The main advantages of this method are due to the simplicity and the flexibility of the custom flux probe with its amplification and filtering stage. The flux probe can be easily positioned on the machines and adapted to a wide range of power levels. The paper also reports an extensive survey on the stray flux based fault detection methods for induction motors, prior to introducing a novel sensor/diagnostic scheme.
It is shown that, given any finite set of pairs of random events in a Boolean algebra which are correlated with respect to a fixed probability measure on the algebra, the algebra can be extended in such a way that the extension contains events that can be regarded as common causes of the correlations in the sense of Reichenbach's definition of common cause. It is shown, further, that, given any quantum probability space and any set of commuting events in it which are correlated with respect to a fixed quantum state, the quantum probability space can be extended in such a way that the extension contains common causes of all the selected correlations, where common cause is again taken in the sense of Reichenbach's definition. It is argued that these results very strongly restrict the possible ways of disproving Reichenbach's Common Cause Principle.
A modular stator switched reluctance motor (SRM) for fault tolerant drive systems is proposed. Owing to the particular construction of the stator there is no mutual coupling between adjacent phases. Hence, the motor can work also when a part of the coils is faulted and the faulted modules can be replaced without uncoupling the machine from the load or gearbox. The sizing particularities are presented and the mathematical model of the motor is developed. The results obtained via finite element analysis are compared with the analytical ones, and with that resulting after testing the constructed laboratory model. All these prove that the proposed SRM can be used in safety-critical drives.
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