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Short-circuit faults in permanent magnet (PM) machines have consistently been a hindrance for safety-critical applications. However, short-circuit currents, especially turn-to-turn short-circuit currents, are difficult to detect and suppress in a timely manner. This article investigates the automatically variable impedance characteristics of the toroidal winding, which restricts the turn-to-turn short-circuit current to an allowable level without terminal short circuit. An analytical model considering the saturation effect of toroidal winding is proposed to reveal the fault tolerance mechanism as well as the mapping relationship between yoke-annular-leakage and fault-tolerant performance. It is found that variable impedance PM machines with toroidal winding have superior fault tolerance performance compared to conventional fractional-slot concentrated-winding and lap winding. Besides, there is a contradictory relationship between its fault tolerance and electromagnetic performance. Furthermore, the laws of phase belt angle and pole number on the electromagnetic and fault-tolerant performance of toroidal winding are first presented in this article. The design criteria and the feasible pole-slot combinations that have inherent fault-tolerant capability are given. Finally, the prototype is built and tested. The experimental results match well with the analytical ones.

Fault diagnosis systems based on search coils are widely used for detecting the interturn short-circuit fault, which is one of the most common electrical faults in electrical machines. Although various search coil structures have been proposed, there is not a systematic method proposed for the design of search coils. In addition, there is not a quantitative evaluation standard to evaluate the performances of search coils in each aspect, making it difficult to judge whether the proposed search coil structure is the optimal one. In this article, the reliability, sensitivity and positioning ability of search coils are derived and evaluated by four defined characteristic indexes. And based on these four characteristic indexes, a systematic search coil design method based on the mutual inductance matrix is also proposed. With the proposed design method, the optimal search coil structures for different permanent magnet synchronous machines are designed and optimized. It is found that the search coils designed by the proposed method have good performance in reliability, sensitivity and positioning ability. The performances of designed search coils are validated by the finite element analysis and experiment.

The compound FR901379, a sulfated echinocandin produced by the filamentous fungus Coleophoma empetriF-11899, is an important intermediate for the synthesis of the antifungal drug micafungin. In this study, we established an efficient clustered regularly interspaced short palindromic repeats/Cas9-based gene editing tool for the industrial production strain C. empetriSIPI1284. With this method, the efficiency of gene mutagenesis in the target locus is up to 84%, which enables the rapid gene disruption for the analysis of FR901379 biosynthetic genes. Next, we verified the putative functional genes of the FR901379 biosynthetic gene cluster via gene disruption and gene complementation in vivo. These core functional genes included the nonribosomal peptide synthetase gene (CEnrps), the fatty-acyl-AMP ligase gene (CEligase) responsible for the formation of the activated form of palmitic acid and its transfer to CEnrps, four nonheme mononuclear iron oxygenase genes (CEoxy1, CEoxy2, CEoxy3, and CEoxy4) responsible for the synthesis of nonproteinogenic amino acids, l-homotyrosine biosynthesis genes (CEhtyA-D), two cytochrome P450 enzyme genes (CEp450-1and CEp450-2), and a transcription regulator gene (CEhyp). In addition, by screening the whole genome, we identified two unknown genes (CEp450-3and CEsul) responsible for the sulfonyloxy group of FR901379, which were separated from the core FR901379 biosynthetic cluster. Furthermore, during gene disruptions in the research, we obtained a series of FR901379 analogues and elucidated the relationship between the groups and antifungal activities.