This paper presents a low-cost fault-tolerant system for open-phase fault in a power converter fed permanent magnet synchronous machine. The proposed fault-tolerant system is based on field orientation control with additional fault tolerance functionality. A current predictive method for open-phase fault detection is presented, together with an estimation of the threshold level for detection. The proposed method is based on the prediction of stator current for the next sampling interval. Furthermore, a new method for post-fault operation of the machine is proposed. For optimal performance of the complete drive a pre-firing angle is introduced in order to avoid the temporary generation of negative torque. This improvement increases the average generated post-fault electromagnetic torque, and consequently it reduces the mechanical stress on various machine parts. The proposed fault detection and postfault operation solutions were simulated in Matlab, and they were also tested on an experimental setup. The results show several advantages of the proposed fault-tolerant solution, like its short fault-detection time, substantial robustness against variation of machine parameters or load fluctuations, and negligible implementation costs, since no hardware modifications are needed. The fault detection algorithm does not require high computing power, and it operates well even during transients.

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In this paper first a current predictive method for single open-phase fault detection in a three phase drive with a permanent magnet synchronous machine is presented. The proposed method is based on a predictive stator current calculation. For each sampling interval the difference between the actual stator current and its predicted value in a previous sampling interval is calculated. To identify the location of a single open-phase fault, an identification method is presented which is based on the analysis of the stator current vector angle. After the single open-phase fault is detected and identified it is desirable for the electrical machine to continue operating with a reduced number of phases. For this purpose, a modified direct torque control algorithm for the fault-tolerant control is implemented. In order to improve the performance of the drive, a pre-firing angle is additionally introduced. All proposed methods have been simulated in Matlab/Simulink and verified on an experimental model. Detekcija odspojene faze i na kvarove otporno upravljanje pretvaračem napajanim sinkronim motorom s permanentnim magnetima. Učlanku je prvo predstavljena metoda za detekciju kvara odspojene faze u trofaznom elektromotornom pogonu sa sinkronim motorom s permanentim magnetima zasnovana na predikciji struja statora. U svakom koraku uzorkovanja računa se razlika izmeu trenutne mjerene struje statora i prediktirane vrijednosti iz prethodnog koraka. U svrhu odreivanja lokacije odspojene faze, predstavljena je metoda identifikacije zasnovana na analizi kuta vektora struje statora. Nakon otkrivene i utvrene odspojene faze, poželjno je nastaviti rad električnog stroja sa smanjenim brojem faza. U ovu svrhu implementiran je izmijenjeni algoritam izravnog upravljanja momentom za postizanje na kvarove otpornog upravljanja. Da bi se unaprijedilo vladanje sustava elektromotornog pogona, dodatno je uveden kut prethoenja aktivacije impulsa. Sve predložene metode simulirane su u Matlab/Simulink okruženju i provjerene na eksperimentalnom postavu.Ključne riječi: Sinkroni motor s permanentnim magnetima, na kvarove otporan sustav, kvar jedne odspojene faze, na kvarove otporno upravljanje, kut prethoenja aktivacije impulsa