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Analytical method for vibration and noise prediction in electrical machines is computationally efficient and widely used. In conventional analytical approaches, the slotted stator is simplified as a cylinder, and it is generally believed that the vibration is more sensitive to the air-gap forces with low spatial orders, hence, those high-order air-gap forces are usually neglected. In this paper, the force distribution on the slotted stator is analyzed using a force transformation model and a new phenomenon, i.e., the modulation effect, is found, which indicates that a high-order air-gap force could also induce a low-mode stator vibration with a large amplitude. As a result, the conventional analytical methods are not so accurate for machines with a strong modulation effect, such as fractional-slot concentrated-winding machines. The existence condition for the modulation effect is also discussed in this paper. Finite-element analysis and experiments have been done to verify the analysis results. [ABSTRACT FROM AUTHOR]

Based on the nonlocal Kirchhoff plate theory, the thermo-electro-mechanical vibration responses are studied for a rectangular piezoelectric nanoplate resting on viscoelastic foundation with various boundary conditions. In doing this, the governing equations of motion are first derived for vibration analysis, where thermo-electro-mechanical loadings, nonlocal effect, piezoelectric effect and viscoelastic foundation have been taken into consideration. Subsequently, the Galerkin strip distributed transfer function method is proposed to solve the governing equations, which enables one to obtain the semi-analytical solutions of natural frequencies for piezoelectric nanoplates with arbitrary boundary conditions. Here, the developed mechanics model is first validated by comparing the obtained results with those available in the literature. Also, the effects of nonlocal parameter, boundary conditions, viscoelastic foundation, external electric voltage, increment temperature, biaxial force and geometric dimensions on the vibration behaviors are carefully examined for the piezoelectric nanoplate. The results demonstrate the efficiency and robustness of the developed model for vibration analysis of a complicated multi-physics system comprising piezoelectric nanoplates, viscoelastic foundation and thermo-electro-mechanical loadings. [ABSTRACT FROM AUTHOR]

Magnetic forces in electrical machines cause vibrations on the structure and its connected components. This leads to undesired noise and vibration in the total system. This paper deals with explanation and reduction of alternating force generation at the connection point of a motor due to radial forces acting on the stator teeth with an electric wheel hub drive being used as example. These alternating forces have a disturbing effect on the driver in the form of noise or vibrations. In our research, we developed a multi-physical simulation of the system which is compared with an operational vibration analysis from an experiment. The simulation shows that the main cause is the axially asymmetric structure of the housing. We reduced the alternating forces at the connection point by using an axially symmetric structure. An axially symmetric design also of other electric machines is to be expected to significantly improve the vibro-acoustic behaviour. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of monitoring and diagnosis of the vibrations level that occurs in the electrical machines operation. Based on the references in the field, a synthesis of all of these problems is carried out. Concerning the measurements needed to assess the parameters of the vibrations, the results obtained using the laser device Easy laser from Damalini to verify the misalignment of the shafts are presented. In the same context the measurements of vibration on the high voltage electric generator from Cummings Companies using the SEO Analyzer software and the data acquisition instrument from NI Compact DAQ 9188 model, are presented. [ABSTRACT FROM AUTHOR]

In this paper, the influence of slot harmonics on magnetic forces and vibration is studied in a 120-slot/116-pole low-speed PM machine at no-load. It is shown how the lowest mode of vibration is produced at no-load due to slotting. Comparing the cases of open slots, semi-closed slots and magnetic wedges, the effect of slot closure on radial forces and torque production capability is discussed. Magnetic flux distribution in the airgap is computed using finite element analysis. Spatial harmonics due to slotting are investigated in different cases. Maxwell's stress tensor is employed to calculate radial and tangential components of the force density in the airgap. Spatial distribution of the total forces on the teeth and also time-dependent force waveform on one tooth are analyzed and discussed for different cases. It is shown how the magnitude of the lowest mode of vibration is reduced in the case of using semi-closed slots and magnetic wedges. Tangential force density distribution and torque production capability are also discussed. Structural analysis is presented to compute the maximum amplitude of the stator deformations due to the radial forces. Experimental results of the prototype generator are presented verifying the existence of the lowest mode of vibration at no-load because of the slot harmonics. [ABSTRACT FROM PUBLISHER]

An air-cored tubular linear generator is designed and prototyped, to capture transient bridge vibrations to power wireless sensors on a bridge. The relationship between the moving mass, the spring, and the damping for harvesting sufficient vibration energy is developed. The voltage and power of the linear generator with sinusoidal speed are obtained with a transient electromagnetic field analysis. Finally, the ambient experimental results of the linear generator are obtained and analyzed from actual bridge vibrations. [ABSTRACT FROM AUTHOR]

Induction motors are critical components for most industries. Induction motor failures may yield an unexpected interruption at the industry plant. Several conventional vibration and current analysis techniques exist by which certain faults in rotating machinery can be identified; however, they generally deal with a single fault only. Instead, in real induction machines, the case of multiple faults is common. When multiple faults exist, vibration and current are excited by several fault-related frequencies combined with each other, linearly or nonlinearly. Different techniques have been proposed for the diagnosis of rotating machinery in literature, where most of them are focused on detecting single faults and few works deal with the diagnosis and identification of multiple combined faults. The contribution of this paper is the development of a condition-monitoring strategy that can make accurate and reliable assessments of the presence of specific fault conditions in induction motors with single or multiple combined faults present. The proposed method combines a finite impulse response filter bank with high-resolution spectral analysis based on multiple signal classification for an accurate identification of the frequency-related fault. Results show the methodology potentiality as a deterministic detection technique that is suited for detecting multiple features where the fault-related frequencies are very close to those analytically reported in literature. [ABSTRACT FROM AUTHOR]

Abstract: In contrast with fully controllable systems, a super articulated mechanical system (SAMS) is a controlled underactuated mechanical system in which the dimensions of the configuration space exceed the dimensions of the control input space. The objectives of the research are to develop a novel SAMS model which is called beam–cart–seesaw system, and renovate a novel approach for achieving a high performance active–passive piezoelectric vibration absorber for such system. The system consists of two mobile carts, which are coupled via rack and pinion mechanics to two parallel tracks mounted on pneumatic rodless cylinders. One cart carries an elastic beam, and the other cart acts as a counterbalance. One adjustable counterweight mass is also installed underneath the seesaw to serve as a passive damping mechanism to absorb impact and shock energy. The motion and control of a Bernoulli–Euler beam subjected to the modified cart/seesaw system are analyzed first. Moreover, gray relational grade is utilized to investigate the sensitivity of tuning the active proportional-integral-derivative (PID) controller to achieve desired vibration suppression performance. Consequently, it is shown that the active–passive vibration absorber can not only provide passive damping, but can also enhance the active action authority. The proposed software/hardware platform can also be profitable for the standardization of laboratory equipment, as well as for the development of entertainment tools. [Copyright &y& Elsevier]

In this paper dynamic behavior of a rotating electric machine subjected to parametric excitation caused by an axial thrust and a forcing excitation caused by an unbalanced force of the rotor is analytically investigated. In order to obtain analytical solution, the Extended Homotopy Analysis Method (EHAM) is employed, which have a distinct advantage in that this procedure is valid even if the considered equation does not contain any small or large parameter. In order to validate the obtained analytical results, numerical simulations were performed and a very good agreement was found. [ABSTRACT FROM AUTHOR]

Artificial neural networks (ANNs) have been used to detect faults in rotating machinery for a number of years, using statistical methods to preprocess the vibration signals as input features. ANNs have been shown to be highly successful in this type of application; in comparison, support vector machines (SVMs) are a more recent development, and little use has been made of them in the condition monitoring arena. The availability of a limited amount of training data creates certain problems for the use of SVMs, and a strategy is advanced to improve the generalisation performance in cases where only limited training data is available. This paper examines the performance of both types of classifiers in two-class fault/no-fault recognition examples and the attempts to improve the overall generalisation performance of both techniques through the use of genetic algorithm based feature selection process. [Copyright &y& Elsevier]

Presents the results of an experimental and theoretical analysis of data acquisition aspects for vibration fault detection and isolation systems in electric drives with unbalanced rotor. Description of the plant used in the study; Details of the structure of vibrations at the experimental plant; Analysis of the vibration signatures.

Presents a framework for the detection and identification of machine faults through vibration measurements and higher order statistics (HOS) analysis. HOS-based methods; Application of technique to classify synthetic mechanical and electrical faults of induction machines compared with their normality; Approaches to perform preventive maintenance in rotating machinery.

Describes a novel method of detecting and unambiguously diagnosing the type and magnitude of three induction machine fault conditions from the single sensor measurement of the radial electromagnetic machine vibration. Application of the method to sinusoidally and inverter-fed induction machines; Automation of the methods into a generalized condition-monitoring tool of commercial viability.

It is established that the vibrations of a rotating shell excite the vibrations of the whole system consisting of a cylindrical shell, an electric motor, and a reducer on a common elastic base. It is shown that the vibrational accelerations excited by two different methods approach each other when the angle of the shell axis changes [ABSTRACT FROM AUTHOR]