Search

Condition monitoring plays a pivotal role in safeguarding three‐phase induction motors (IMs) commonly utilized in industrial and commercial settings. This study focuses on wound rotor induction motors (WRIMs), specifically addressing the adverse impact of the stator and rotor winding inter‐turn short circuits. Unlike prevalent literature concentrating on squirrel cage induction motors (SCIMs) and emphasizing stator inter‐turn and broken rotor bar faults, this paper introduces a comprehensive technique applicable to detecting inter‐turn faults (ITFs) in WRIMs. The proposed method ensures stable motor operation and averts catastrophic failures.Experimental validation is conducted on a three‐phase, 7.5 hp, 415 V WRIM, affirming the technique's effectiveness under conditions of unbalanced source voltages and asymmetries in stator and rotor windings. The approach employs motor currents‐based experimental emulation, utilizing loci of instantaneous symmetrical components of three‐phase stator currents, £ (is1 – is2) and rotor currents £ (ir1 – ir2) for stator and rotor ITFs detection, respectively. Termed the ‘Wing Technique’ (WT), this method derives its name from the distinctive ‘Wing Shape’ formed by these loci. [ABSTRACT FROM AUTHOR]

This paper proposes a novel three-phase 24-pulse diode converter topology derived from cascading two 12-pulse rectifiers. Unlike existing designs that use multi-tap Interphase Reactors (IPR) or transformers, our configuration eliminates the need for interface transformers or reactors, significantly reducing cost and complexity. The topology provides galvanic isolation between input and output, making it suitable for high-power applications like high voltage direct current (HVDC) transmission. Theoretical analysis shows the design achieves low input current harmonic distortion by canceling harmonics up to the 21st order. Experimental results from a reduced-scale 500W prototype validate the topology, demonstrating an output voltage of 547.6V, input current total harmonic distortion (THD) of 4.4%, and efficiency of 87.4% at full load. This simple yet effective design offers a competitive balance of performance and practicality for multi-pulse AC-DC conversion.

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Background In general, the diagnosis of pedicle screw (PS) loosening is evaluated qualitatively based on the presence of a radiolucent area around the implant wider than 1 mm on plain radiographs and computed tomography (CT). Digital tomosynthesis is a novel imaging technology that can acquire reconstructed tomographic images of patients in different postures with relatively low radiation. In this study, PS loosening is evaluated quantitatively by measuring the PS displacement angle in the vertebrae using digital tomosynthesis. Methods We evaluated 41 patients who underwent posterior spinal fusion surgery using PS. The 72 pedicle screws at the cranial end of the fused segments were evaluated. The patients were divided in two groups, one with PS loosening (7 patients, 12 screws) and the other without PS loosening (34 patients, 60 screws), based on conventional CT findings. All patients underwent tomosynthesis in two different postures during a single CT session. Results The displacement angles of the PS in patients in a lying position and in a standing position were measured using selected slices of the same cross-sectional view from digital tomosynthesis. The displacement angle was significantly greater in the PS loosening group (5.7°) than in the group without PS loosening (0.6°) (p

Background: In general, the diagnosis of pedicle screw (PS) loosening is evaluated qualitatively based on the presence of a radiolucent area around the implant wider than 1 mm on plain radiographs and computed tomography (CT). Digital tomosynthesis is a novel imaging technology that can acquire reconstructed tomographic images of patients in different postures with relatively low radiation. In this study, PS loosening is evaluated quantitatively by measuring the PS displacement angle in the vertebrae using digital tomosynthesis.Methods: We evaluated 41 patients who underwent posterior spinal fusion surgery using PS. The 72 pedicle screws at the cranial end of the fused segments were evaluated. The patients were divided in two groups, one with PS loosening (7 patients, 12 screws) and the other without PS loosening (34 patients, 60 screws), based on conventional CT findings. All patients underwent tomosynthesis in two different postures during a single CT session.Results: The displacement angles of the PS in patients in a lying position and in a standing position were measured using selected slices of the same cross-sectional view from digital tomosynthesis. The displacement angle was significantly greater in the PS loosening group (5.7°) than in the group without PS loosening (0.6°) (p<0.01). Based on the ROC analysis, the optimal cut-off value of the PS displacement angle for identification of loosened screws was 1.7° with a sensitivity of 100% and specificity of 93% (AUC = 0.98).Conclusions: This new method using digital tomosynthesis has the potential to aid diagnosis of PS loosening quantitatively and more accurately than conventional evaluations. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper provides theoretical and experimental discussions on the characteristics of the modular multilevel converter (MMC) when phase-shifted carrier sinusoidal pulse-width modulation (PSC-SPWM) is applied. Harmonic-cancellation characteristics of output voltage and circulating current are analyzed on the basis of a general implementation of PSC-SPWM with two freedom displacement angles. Five available PSC-SPWM schemes with different carrier displacement angles were obtained, and a detailed performance comparison about output voltage and circulating current harmonic characteristics is presented. On the basis of the equivalent circuit with ideal transformer representation of the SMs, capacitor voltages affected by PSC-SPWM schemes are also briefly analyzed. The proposed PSC-SPWM schemes can unify two different cases of odd and even SM situations for output voltage and circulating current harmonic minimization, respectively. Lastly, the optimal schemes for practical MMC application were verified by simulation and experiments on an MMC prototype.

A microseismic monitoring technique is adopted to investigate the distribution regularity of microseismic events released by the coal mining - induced roof rock mass along the vertical and horizontal directions in combination with mine geological data. On the basis of the quantity and energy distributions of the microseismic events recorded using the microseismic monitoring technique, a zoning method is first established for the roof strata movement in the vertical and horizontal directions. The vertically zoning method is then applied to analyze the microseismic monitoring results obtained in the Dongjiahe Coal Mine, which divides rock mass into six zones along the vertical direction, i.e. the caved zone, the block zone, the vertical fracture through-going zone, the vertical fracture zone, the separation zone and the continuous zone. The horizontally zoning model divides the roof strata movement into three zones, i.e. the calm zone, the generation zone impacted by working face and the historical generation zone. After that, based on the horizontally zoning model, a method is developed to determine the displacement angle using the microseismic monitoring data, which has been verified in the Dongjiahe Coal Mine. [ABSTRACT FROM AUTHOR]

Gravitropism of maize and rice coleoptiles was investigated with respect to its dependence on the angle of displacement or the initial stimulation angle (ISA). Close examination of curvature kinetics and the response to a drop in stimulation angle (SA) indicated that the gravitropic response during an early but substantial part of curvature development is directly related to the ISA, there being no effect of the reduction of SA resulting from the curvature response itself. On the basis of this finding, the relationship between the steady SA and the curvature rate was determined. In maize, the curvature rate increased linearly with the sines of SAs up to an SA of 90°. Rice coleoptiles, however, showed a saturation curve in the same range of SAs. The saturation profile was nearly identical between coleoptiles grown in air and those submerged in water, although the latter elongated much faster. Rice coleoptiles appeared to be far more sensitive to gravity than maize coleoptiles. It is concluded that the sensitivity to gravity, assessed through dependence on ISA, is a property inherent to a given gravitropic organ. Long-term measurements of curvature indicated that the coleoptiles bend back past the vertical. This overshooting was marked in submerged rice coleoptiles. [ABSTRACT FROM AUTHOR]

This paper provides theoretical and experimental discussions on the characteristics of the modular multilevel converter (MMC) when phase-shifted carrier sinusoidal pulse-width modulation (PSC-SPWM) is applied. Harmonic-cancellation characteristics of output voltage and circulating current are analyzed on the basis of a general implementation of PSC-SPWM with two freedom displacement angles. Five available PSC-SPWM schemes with different carrier displacement angles were obtained, and a detailed performance comparison about output voltage and circulating current harmonic characteristics is presented. On the basis of the equivalent circuit with ideal transformer representation of the SMs, capacitor voltages affected by PSC-SPWM schemes are also briefly analyzed. The proposed PSC-SPWM schemes can unify two different cases of odd and even SM situations for output voltage and circulating current harmonic minimization, respectively. Lastly, the optimal schemes for practical MMC application were verified by simulation and experiments on an MMC prototype. [ABSTRACT FROM AUTHOR]