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In order to relieve the problem of bearing wear in high-speed permanent magnet generator, a semi-symmetrical double winding structure with the same number of poles is proposed in this paper. The coupling of the winding magnetic fields enables the rotor to be subjected to a radial electromagnetic force along the direction of overcome gravity, which could effectively extend the service life of the bearings. Firstly, the design principle of the semi-symmetrical double winding structure and the winding MMF are analyzed based on the AC machine winding theory, and the elliptical magnetic field characteristics of the harmonic winding are clarified. Combining the characteristics of order and frequency for harmonic magnetic field, the magnetic fields coupling mechanism of the double winding is revealed, and the analytic model of the power generation and radial electromagnetic force are determined. Secondly, based on rolling contact fatigue theory, the service life improvement of bearing by the double winding structure is certificated. In addition, the magnetic fields of double winding are decoupling calculated by using the finite element method, and the consistency of results between the theoretical analyses and the finite element calculations is determined. Finally, the calculation accuracy of the finite element analysis is demonstrated by experiments on the prototype. [ABSTRACT FROM AUTHOR]

In order to solve the problem of insufficient torque for flux weakening in permanent magnet machines, a novel flux–torque regulation hybrid excitation machine with axial–radial magnetic circuit (FTRHEM) is proposed. To solve the problem that the cogging torque of the proposed machine is caused by multiple factors and the coupling relationship is complicated, an analytical expression for the cogging torque is derived first. Then, the influence of the axial excitation device on the cogging torque is determined. The influence mechanism of the relative position between the axial excitation device and stator on the cogging torque is revealed. A dislocation method is proposed to reduce the cogging torque, and its effectiveness is verified by finite element analysis (FEA). Furthermore, the reduction of the cogging torque in FTRHEM with different pole–slot combinations by this method is comprised and analyzed, which demonstrates the feasibility of the method. Finally, the FEA results are combined with experiments to verify the accuracy of simulations. [ABSTRACT FROM AUTHOR]

Aiming at the problems of the low output torque and low overload capacity of induction motors caused by the decrease in the main flux at high speeds, the influence of split-winding on motor performance is studied in this paper, and the performance of the motor is optimized by a study of the winding split turns and winding split segments. First, the influences of winding turns and frequency on motor performance parameters are analyzed by an analytical algorithm, and the mechanism of split-winding on motor performance is revealed. Second, the performance of the motor before and after winding splitting is calculated by the finite element method, and the influences of winding splitting on the output torque and overload capacity are clarified. Through the study of the winding split turns and the number of winding split segments, the best speed at the winding split and the optimum number of winding split segments are determined, which provides a basis for the winding split principle when an induction motor is designed with split-winding. Finally, the performance of a prototype before and after a winding split is tested and the accuracy of the finite element calculation is verified. [ABSTRACT FROM AUTHOR]

Low-phosphorus stress significantly impacts the development of maize kernels. In this study, the phosphor efficient maize genotype 082 and phosphor deficient maize genotype Ye107, were used to construct an F2:3 population. QTL mapping was then employed to determine the genetic basis of differences in the maize kernel traits of the two parents in a low-phosphorus environment. This analysis revealed several major QTL that control environmental impacts on kernel length, width, thickness, and weight. These QTL were detected in all three environments and were distributed on five genome segments of chromosomes 3, 5, 6, and 9, and some new kernel-trait QTL were also detected (eg: Qkwid6, Qkthi3, Qkwei9, and Qklen3-1). These environmentally insensitive QTL can be stably expressed in low phosphorus environments, indicating that they can lay a foundation for the breeding of high phosphorus utilization efficiency germplasm. [ABSTRACT FROM AUTHOR]

The introduction of suspension winding generates radial suspension force in bearingless permanent magnet synchronous motors (BPMSMs). However, the addition of suspension winding in the stator slots reduces the slot area of the torque winding. This results in a decrease in the motor torque characteristics, while the thermal load increases. Therefore, to obtain the optimal operating performance of the motor, the variations in torque performance and suspension characteristics are studied with the slot area allocation ratio (SAAR) of the dual winding in this paper. First, the expressions for the electromagnetic torque and radial suspension force with SAAR are derived by the Maxwell tensor method. The effects of the winding parameters on the BPMSM performance are determined and the influences of the current and turn number of the dual winding are considered in the expressions. Subsequently, the effects of thermal load on the torque and suspension force are analyzed by the finite element method (FEM). The optimal motor operating performance with the total thermal load constraint is determined. On this basis, the effects of the dual winding SAAR on the torque and suspension force are studied, the coupling relationship between the torque and the suspension force is obtained, and the optimal matching relationship of the torque and the suspension force at different SAAR values are determined. Finally, the accuracy of the analyses is confirmed by performing static and dynamic experiments on a prototype. [ABSTRACT FROM AUTHOR]

Head smut (HS) is one of the most devastating diseases of maize in spring production regions in China. Quantitative trait loci (QTL) for HS resistance were identified in this study to provide theoretical and applied tools for breeding HS resistance in maize. QTL associated with HS resistance were identified in a F2:3 population derived from a T32 (highly resistant genotype) × HC (highly susceptible genotype) cross. Analysis in each of three environments and a collective analysis across all three environments were used to identify QTL in the F2:3 population. A significant difference in HS resistance was found between the inbred lines, 'T32' and 'HC'. Large genetic variation and transgressive segregation in the F2:3 population were observed between the three different sites, Guian (GA), Huaxi (HX), and Pingba (PB). Two stable and novel QTL for resistance to HS were detected in the different environments that were located within the bnlg1014 to umc2224 (qHS1) interval on chromosome 1 and in the umc1006 to umc1857 (qHS6) interval on chromosome 6. Both QTL can be used for further fine mapping, marker-assisted selection breeding, and theoretical studies on HS resistance in maize. [ABSTRACT FROM AUTHOR]

The stator–rotor slot combination is an important parameter in the design of high-voltage induction motor (HVIM). The different design of the stator–rotor slot combination will have an effect on the performance of the HVIM, such as torque, air-gap flux density, loss and so on. In order to analyze its influence, 10 kV, 1000 kW HVIM is taken as an example and the finite element model is established. The correctness of the model is verified by experiments. Firstly, based on the finite element method, the electromagnetic field of HVIM with different rotor slots is solved, and performance parameters of the HVIM are obtained. Based on these parameters, the air-gap magnetic density, overload capacity, average torque and torque ripple of the HVIM are studied, and the distribution rules under the different number of rotor slots are obtained. In addition, the difference of stator core loss and rotor eddy current loss of different rotor slots is analyzed, and the variation mechanism of loss change is revealed. Finally, the performance parameters of the HVIM with different rotor slots are compared, and the reasonable number of rotor slots is obtained. The conclusion of this paper provides reliable theoretical guidance for improving motor performance. [ABSTRACT FROM AUTHOR]

The permanent magnet thickness (PMT) is an important parameter in the design of the permanent magnet machine, and it directly affects the air-gap magnetic field and performance of generator. In this paper, a 117-kW, 60,000-rpm, high-speed permanent magnet generator (HSPMG) is taken as an example, and a two-dimensional finite element model (FEM) is established. By comparing calculation result and test data, the accuracy of the model is verified. The air-gap flux density waveform is obtained by the FEM, and the waveform is decomposed by the Fourier transform principle. The nonlinear variation law of harmonic content with the increase in PMT is obtained, and the nonlinear variation mechanism of air-gap flux density is revealed. On this basis, the variation law of voltage and voltage regulation with the increase in PMT is given, and the PMT is optimized. In addition, the nonlinear variation law of the loss is determined. The research shows that the purpose of optimizing performance of HSPMG can be achieved by adjusting the PMT. The PMT is finally determined when the generator performance is optimal. The conclusions provide some reference for the research of HSPMG. [ABSTRACT FROM AUTHOR]

To provide theoretical and applied references for acid phosphatase (APase) activity of maize, this study was to identify quantitative trait locus (QTL) for APase activity in root and rhizosphere soil of maize under low phosphorus (p) stress. The correlation and the QTL of APase activity in root (APR) and APase activity in rhizosphere soil (APS) were studied for the F population derived from the cross 082×Ye107 under low P stress in two sites. Analysis for each environment and joint analysis across two environments were used to identify QTL for the F population. A significant difference in APR and APS was found between 082 (P efficient genotype) and Ye107 (P deficient genotype). A large genetic variation and transgressive segregation of the F population were observed in Beibei and Hechuan. One stable QTL for APR was detected in different environments, which was located in the interval bnlg1350 to bnlg1449 on chromosome 3. Two stable QTLs for APS were detected, which were located in the interval umc2083 to umc1972 on chromosome 1 and in the interval umc2111 to dupssr10 on chromosome 5. The stable QTLs can be used in MAS breeding and theoretical study of maize. [ABSTRACT FROM AUTHOR]

Acid phosphatase (APase) is very important in phosphorus (P) scavenging and remobilization in plants. The aim of this study was the fine mapping of quantitative trait loci (QTL) for APase activity (APA) in maize ( Zea mays L.) leaf. The QTL for APA were studied in the F2:3 population derived from the cross 082 × Ye107 under low P stress in two sites. A significant difference in APA was found between 082 (P-efficient genotype) and Ye107 (P-deficient genotype). Each environment was analyzed to identify the QTL. Six QTL for APA were found, comprising two QTL at Beibei (BB) and four QTL at Hechuan (HC), China. A QTL denoted as AP9 showed a stable expression under different environments on chromosome 9, and explained 10.21 and 16.81 % of phenotypic variation at BB and HC, respectively. For the fine mapping of this QTL, seven individuals selected via marker-assisted selection in the BC3F1 population were used to produce the BC3F2 lines by selfing and to allow recombination within the region containing the target QTL. High-resolution genetic and physical maps were further constructed for the fine mapping of AP9 using 12 simple sequence repeat markers and the BC3F2 population consisting of 1,441 individuals. As a result, the location of AP9 was narrowed down to a 546-kb fragment on chromosome 9. [ABSTRACT FROM AUTHOR]

Due to its simple and robust structure with no windings or PMs on the rotor, the doubly salient motor has been studied in recent years for potential use. However, relatively low torque density and high torque ripples are the main obstacles to its development. To simultaneously improve the torque characteristics and enhance the flux regulation capability, a novel 18/11-pole hybrid excitation doubly salient motor (HEDSM) with a new winding structure is proposed in this paper, with the structure and working principle described. The influence of parameters is analyzed, based on which the motor is optimized. After that, the working performance, including the flux linkage, the back-EMF, the torque characteristic, the flux regulation capability, and motor losses, are investigated in detail by finite element analysis. By comparing the novel HEDSM with the traditional doubly salient electromagnetic motor (DSEM), excellent torque performance and flux regulation capability are revealed. [ABSTRACT FROM AUTHOR]