Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.

Parameter Design for a High-Speed Permanent Magnet Machine Under Multiphysics Constraints

Abstract: Regarding high-speed permanent magnet machines (HSPMMs), there is a lack of complete and detailed design processes for main parameters under multiphysics constraints, which makes it difficult to obtain high-reliability designs for designers of HSPMMs. This paper presents a detailed and complete design process for the main parameters of an HSPMM under multiphysics constraints. Firstly, the initial sizes are obtained through electromagnetic and mechanical design theory. Then, the influence of design parameters on rotor stress is analyzed in detail, including PM material, rotor temperature, sleeve thickness, PM thickness and rotor diameter. Furthermore, the rotor dynamics have also been studied in detail, including the effects of bearing stiffness, impeller mass, rotor diameter, core length, and gyroscopic effect on critical speed. Afterwards, the comprehensive research on the electromagnetic filed and the loss characteristics is performed. The cooling system is designed and the thermal field is also studied in Ansys-Cfx. Besides, the coupled temperature-stress analysis is established considering the interaction between temperature and mechanical characteristics. Finally, a full-size HSPMM prototype has been fabricated and tested to validate the detailed multiphysics design process.

Monitoring lane changes by motor vehicle involves using distance sensors to monitor semi-areas for whether vehicles/obstructions are located or approaching with critical speed in other lanes

Abstract: The method involves using electronic detection of lane markings, whereby an acoustic and/or visual warning signal is generated in critical situations. Lane monitoring is combined with camera-aided electronic image evaluation of the semi-area in front of and/or behind the motor vehicle. Distance sensors (10) are used to monitor the semi-area for whether vehicles or obstructions are located or approaching with critical relative speed in the other lanes.

Double frequency sliding and wavelet analysis for rotor fault diagnosis in induction motors under time-varying operating condition

Abstract: The detection of rotor faults in squirrel cage motors has long been an important but difficult matter in the area of electrical machine diagnosis. Under time-varying condition, the typical rotor fault frequency components (RFFCs), which appear in the phase current spectrum of faulted motors, are spread in a bandwidth proportional to the speed variation and are difficult to detect accurately. Thereby a new diagnosis method based on the combined use of bi-frequency sliding (BFS) and discrete wavelet transform (DWT) is proposed here for stator phase current analysis. Simulation and experimental results are reported to validate the effectiveness of the proposed approach under critical speed varying conditions.