Search

The article presents the technique of modeling spindles of machines for estimating bearing wear and forecast endurance.

This paper deals with the bearing wear and the early detection of possible damages in bearings of variable-speed, converter-fed electrical motors. A description covering the issue of bearing currents in converter-fed drives is presented. However, this work focuses on the practical experiences of bearing wear influence on electric motors performance. Explicit information concerning a bearing damage due to corrugation caused by electrical currents through the bearing can only be extracted by a combined analysis of the electrical and the mechanical behavior of the bearing. For this purpose systematic measurements have to be exploited, where both the electrical measurement of bearing currents and the mechanical measurement of the bearing vibration status have to be combined for determining the bearing condition state. A comparison between different vibration measurement methods provides a systematic approach enabling detection and classification of possible changes in bearings of the drive system i.e. motor and the attached load machine, in a very early state. Finally, a description of the possibilities to determine the electrical bearing load in a drive system and the correlation of its possible limit values to the mechanical bearing condition is highlighted.

Active magnetic bearings can not only solve the bearing wear and life problems but also reduce the loss and noise of bearings, which makes it more and more popular in the use of high speed motor. In this paper, the design procedure and control method are presented for four-axis magnetic bearings designed for a 200kW/40000rpm high speed motor. The working principle and actuator model of magnetic bearings are introduced and graphically illustrated at first. Both analytical method and finite element analysis (FEA) method are used to design the actuator of the magnetic bearings and their results are compared to validate the results. Then the layout of the high speed motor integrated with the designed active magnetic bearings is introduced. To improve the dynamics performance of the high speed motor system, the rotor dynamic of high-speed rotor are also analyzed in detail. In the end, a novel converter for the magnetic bearing drive is introduced. Moreover, an effective control method is simulated in detail and the simulation results show the feasibility of the control method.

Firstly, the concepts and classification about visualized data mining technology have been elaborated in this paper, then the technology of data mining, data visualization and regression analysis are discussed, Finally, combined with the example of sliding bearing wear coefficient test, using data mining, data visualization and regression analysis technology, this paper design a system to implement visualized data mining technology under the web environment.

This paper deals with the early detection and monitoring of possible bearing damage of variable-speed, converter-fed electric motors. After a brief description about the issue of bearing currents in converter-fed drives, the main subject will be outlined with the focus on practical experience. A measurement systemology is used for this purpose, where the electrical measurement of bearing current events as well as the mechanical measurement of the vibration status of the bearing is taken into account. A comparison between different vibration measurement methods leads to a systemology, which allows to detect possible changes in the motor bearing in a very early state of operation.

The basic interrelationships that are required to investigate the cross-system subject of “bearing currents in converter operation”, are discussed in this paper. In order to obtain an integrated overview of the situation, it is decisive that the main points of the investigation are not discussed individually, but must be considered from an overall point of view. Results from the parameter test area and their link to the overall situation are shown. Higher-level systemology to simulate electric currents flowing through a bearing is outlined, taking into account the various processes that take place in the bearing. The paper is completed by presenting a new type of bearing current sensor system. A review of the steps still required is provided in the conclusion.

This paper deals with the diagnosis of faults in roller-element bearings as the core of a dedicated Condition based Maintenance (CBM) system. Vibration signals recorded by accelerometers feed into a classification model in charge of monitoring and evaluating bearing wear. The chosen feature extraction technique is based on the computation of the Discrete Fourier Transform (DFT) and on the estimation of the normalized frequency content in each of the considered spectrum sub-bands as an indicative measure of the state of health of the roller-element bearing. Three different damage attributes have been investigated. For each attribute, both Support Vector Machines (SVM) and neurofuzzy Min-Max classifiers have been employed as the core of the diagnostic system. Test results show that it is possible to achieve high accuracy in all diagnostic problems considered. The pre-processing procedure and the classification stage, especially in the case of Min-Max fuzzy networks, do not require demanding computational hardware resources, and as a result, a simple and effective diagnostic system can be designed by feeding the synthesized Min-Max classifiers with the spectral features computed from vibration sensor outputs.

The main research of the thesis was based on the analysis to the wearing and plugging in the pneumatic conveying pipeline and the elaboration on the mechanism of the accident. Several methods of dealing with ash blocking and several kinds of pipelines which fit for decreasing wear and bearing wear in the pneumatic conveying system were introduced.

Polysilicon variable-capacitance rotary harmonic side-drive micromotors and results from operational and frictional studies of these motors are described. Quantitative studies of wear under electric excitation are also reported. Voltages as low as 26 V across 1.5- mu m gaps are sufficient for operation. Frictional force estimates of 0.15 mu N at the bushings and 0.04 mu N in the bearings are obtained from measurements of stopping voltages. Extended operation of these motors to near 100 million wobble cycles at excitation frequencies of 10000 r.p.m. and 25000 r.p.m. for operational durations of 150 h and 71 h, respectively, are studied. The results indicate that bearing wear is significant and results in changes in the gear ratio of the motors by as much as 20%. Typical gear ratios are near 90 at the start of motor operation and decrease to about 70 as the bearings wear out. >