A Study of Motor Bearing Fault Diagnosis using Modulation Signal Bispectrum Analysis of Motor Current Signals

Failure of induction motors are a large concern due to its influence over industrial production. Motor current signature analysis (MCSA) is common practice in industry to find motor faults. This paper presents a new approach to detection and diagnosis of motor bearing faults based on induction motor stator current analysis. Tests were performed with three bearing conditions: baseline, outer race fault and inner race fault. Because the signals associated with faults produce small modulations to supply component and high nose levels, a modulation signal bispectrum (MSB) is used in this paper to detect and diagnose different motor bearing defects. The results show that bearing faults can induced a detestable amplitude increases at its characteristic frequencies. MSB peaks show a clear difference at these frequencies whereas conventional power spectrum provides change evidences only at some of the frequencies. This shows that MSB has a better and reliable performance in extract small changes from the faulty bearing for fault detection and diagnosis. In addition, the study also show that current signals from motors with variable frequency drive controller have too much noise and it is unlikely to discriminate the small bearing fault component.

Testing and Analysis of Induction Motor Electrical Faults Using Current Signature Analysis

The proposed method deals with the emerging technique called as Motor Current Signature Analysis (MCSA) to diagnosis the stator faults of Induction Motors. The performance of the proposed method deals with the emerging technique called as Motor Current Signature Analysis (MCSA) and the Zero-Sequence Voltage Component (ZSVC) to diagnose the stator faults of Induction Motors. The unalleviated study of the robustness of the industrial appliances is obligatory to verdict the fault of the machines at precipitate stages and thwart the machine from brutal damage. For all kinds of industry, a machine failure escorts to a diminution in production and cost increases. The Motor Current Signature Analysis (MCSA) is referred as the most predominant way to diagnose the faults of electrical machines. Since the detailed analysis of the current spectrum, the method will portray the typical fault state. This paper aims to present dissimilar stator faults which are classified under electrical faults using MCSA and the comparison of simulation and hardware results. The magnitude of these fault harmonics analyzes in detail by means of Finite-Element Method (FEM). The anticipated method can effectively perceive the trivial changes too during the operation of the motor and it shows in the results.

Reduction of current chopping noise with DSP controller in switched reluctance motor drive system

A novel current chopping mode was used in a switched reluctance motor drive system to make full use of the characteristics of digital signal processor (DSP) TMS320F240. The necessity of this 180° phase-shift current control (PSCC) mode is introduced first and then the principle of PSCC covering both hardware requirement and software programming is described in detail. The analysis made indicated that with this mode, the chopping frequency in winding can reach 20 kHz with 10 kHz power switches and the control frequency can reach 40 kHz at the same time. Subsequently, based on the linear and nonlinear mathematical models of the switched reluctance motor (SRM), some simulation work has been done. The simulation results show that when this mode is applied to SRM drive (SRD) system, the current waveform becomes better. So the ripple of the torque is reduced simultaneously and the vibration and acoustic noise are reduced involuntarily. Stationary tests show that the acoustic noise is greatly diminished. Finally, some experiments were made using a 50 kW SRD system for electric vehicle (EV). Experimental results indicate that this mode can be implemented feasibly and it has a good action on the SRD system.

A novel method to calculate the thrust of linear induction motor based on instantaneous current value

Because of the end effect, a linear induction motor （LIM） runs in an asymmetrical state even though the winding of each phase is symmetric. Based on the basic principle of the LIM, a new approach was proposed to calculate the thrust of the LIM using the instantaneous current value. A three-phase LIM model with 12 slots and a singlelayer winding was designed to validate this method. The experiments show that when the current is small, the calculated results basically agree with the experiments. The agreement becomes worse with the increase of the current because of the saturation of the primary iron core. The proposed formula is suitable when the iron core of the LIM primary is in an unsaturated state.

Adaptive current compensation with nonlinear disturbance observer for single-sided linear induction motor considering dynamic eddy-effect

An adaptive current compensation control for a single-sided linear induction motor(SLIM) with nonlinear disturbance observer was developed. First, to maintain t-axis secondary component flux constant with consideration of the specially dynamic eddy-effect(DEE) of the SLIM, a instantaneously tracing compensation of m-axis current component was analyzed. Second,adaptive current compensation based on Taylor-discretization algorithm was proposed. Third, an effective kind of nonlinear disturbance observer(NDOB) was employed to estimate and compensate the undesired load vibrations, then the robustness of the control system could be guaranteed. Experimental verification of the feasibility of the proposed method for an SLIM control system was performed, and it showed that the proposed adaptive compensation scheme with NDOB could significantly promote speed dynamical response and minimize speed ripple under the conditions of external load coupled vibrations and unavoidable feedback control variables measured errors, i.e., current and speed.

A Novel Current Sensor Technique for Brushless DC Motor Drives

The torque output in a permanent magnet brushless DC motor (BLDCM) is usually controlled by regulating the motor phase currents. In this paper, three kinds of PWM strategies together with some critical review on traditional current measurements in a BLDCM drive system are discussed. A novel method for assessing the PWM information and measuring the motor phase currents by a dc link current sensor is proposed. An attractive feature of the proposed method is the simplicity with the current sample processing because there is no need to incorporate the conduction information of the power switches or diodes. Only the single sided PWM or the double sided complementary PWM is needed with the proposed technique.

Effect of Transcranial Direct Current Stimulation of Motor Cortex versus Insula Cortex on Chronic Post-Mastectomy Pain: Randomized Sham-Controlled Trial

Background: Transcranial direct current stimulation (tDCS) across cortical brain areas appears to improve various forms of pain, yet evidence of tDCS efficiency and ideal stimulation target is lacking. This study aimed to compare the add-on analgesic efficacy of concentric electrode transcranial direct current stimulation (CE-tDCS) stimulation over the primary motor cortex versus the insular cortex on the management of chronic postmastectomy pain. Method: Prospective randomized double-blind sham-controlled study enrolled eighty patients with chronic postmastectomy pain that were randomly assigned to four groups: active motor (AM), sham motor (SM), active insula (AI) and sham insula (SI) group, each received 5 sessions for 20-minute duration with 2 mA tDCS over the targeted area of the contralateral side of pain. Our primary outcome was VAS score, the secondary outcomes were VDS score, LANSS score and depression symptoms by HAM-D scores, assessment was done at 4 time points (prestimulation, after 5th session, 15th day and one month after the last session). Results: Both active tDCS groups (motor and insula) showed reduction of VAS (P Conclusion: Active tDCS stimulation either targeting the primary motor cortex or the insula cortex has add-on analgesic effect for controlling neuropathic chronic post mastectomy pain and the maximum effect was at 15 days after the last session.

Current Search: Performance Evaluation and Application to DC Motor Speed Control System Design

This paper proposes the current search (CS) metaheuristics conceptualized from the electric current flowing through electric networks for optimization problems with continuous design variables. The CS algorithm possesses two powerful strategies, exploration and exploitation, for searching the global optimum. Based on the stochastic process, the derivatives of the objective function is unnecessary for the proposed CS. To evaluate its performance, the CS is tested against several unconstrained optimization problems. The results obtained are compared to those obtained by the popular search techniques, i.e., the genetic algorithm (GA), the particle swarm optimization (PSO), and the adaptive tabu search (ATS). As results, the CS outperforms other algorithms and provides superior results. The CS is also applied to a constrained design of the optimum PID controller for the dc motor speed control system. From experimental results, the CS has been successfully applied to the speed control of the dc motor.

Impact of Geomagnetically Induced Currents Secondary Event on the High-Voltage Synchronous Motors

It is justified that during geomagnetic storms the high voltage synchronous engines are being impacted by high current harmonics of even sequences powered by power transformer due to geo-induced high voltage currents flowed through the windings. Equivalent circuits of step down substation and HV synchronous motors are made for making it possible to consider a saturation of power transformer magnetic system and higher current harmonics availability in stator windings. Analytic expressions for higher current harmonics and extra capacity losses calculation in stator windings are received, as well as the calculation of induction torques allowing to denote a rate of geomagnetic processes impact on synchronous engine operation at various step down substation parameters.

Is effect of transcranial direct current stimulation on visuomotor coordination dependent on task difficulty?

Transcranial direct current stimulation （tDCS）, an emerging technique for non-invasive brain stimulation, is increasingly used to induce changes in cortical excitability and modulate motor behavior, especially for upper limbs. The purpose of this study was to investigate the effects of tDCS of the primary motor cortex on visuomotor coordination based on three levels of task difficulty in healthy subjects. Thirty-eight healthy participants underwent real tDCS or sham tDCS. Using a single-blind, sham-controlled crossover design, tDCS was applied to the primary motor cortex. For real tDCS conditions, tDCS intensity was 1 mA while stimulation was applied for 15 minutes. For the sham tDCS, electrodes were placed in the same position, but the stimu- lator was turned off after 5 seconds. Visuomotor tracking task, consisting of three levels （levels 1, 2, 3） of difficulty with higher level indicating greater difficulty, was performed before and after tDCS application. At level 2, real tDCS of the primary motor cortex improved the accurate index compared to the sham tDCS. However, at levels 1 and 3, the accurate index was not significantly increased after real tDCS compared to the sham tDCS. These findings suggest that tasks of mod- erate difficulty may improve visuomotor coordination in healthy subjects when tDCS is applied compared with easier or more difficult tasks.

二维Brownianmotor工作模型

研究了 Brownian(布朗 ) motor在二维耦合的非对称性周期势中同时受热噪声和外部非平衡涨落驱动下的定向输运 ,讨论了耦合对流行为的影响 .发现在二维摇摆棘轮中 ,流和效率的极大值出现在有限温度 ;而在二维关联棘轮中 ,流的极大值比一维的大

Industrial Fault Signals Propagation and Current Signature Analysis

Motor current signature analysis provides good results in laboratory environment. In real life situation, electrical machines usually share voltage and current from common terminals and would easily influence each other. This will result in considerable amount of interferences among motors and doubt in identity of fault signals. Therefore, estimating the mutual influence of motors will help identifying the original signal from the environmental noise. This research aims at modelling the propagation of signals that are caused by faults of induction motors in power networks. Estimating the propagation pattern of fault signal leads to a method to discriminate and identify the original source of major events in industrial networks. Simulation results show that source of fault could be identified using this approach with a higher certainty than anticipated output coming of any individual diagnosis.

Influence of Induction Motor Design Data on Effects of Cage Asymmetry

The purpose of this paper is to analyze influence of design data on a component （1 - 2s）~ in stator currents of induction motors, mainly used for cage fault diagnosis. This paper shows that such an approach does not always lead to a correct outcome. The considerations are based on a ＂classical＂ model of induction motors extended to cage asymmetry by introducing cage asymmetry factors ko~ and ka. It has been found that in order to estimate the level of the component （1 - 2s）7~, it is enough to know the pole-pair number ＂p＂ and the number of rotor slots ＂N＂. The main objective of the paper is to provide engineers with simple qualitative prediction of effects due to cage faults for various motors when information on design data is very limited.

Feedback control of two-headed Brownian motors in flashing ratchet potential

We presented a detailed investigation on the movement of two-headed Brownian motors in an asymmetric potential under a feedback control. By numerical simulations the direct current is obtained. The current is periodic in the initial length of spring. There is an optimal value of the spring constant. And the dependence of the current on the opposing force is reversed. Then we found that when the change of the temperature and the opposing force have optimal values, the Brownian motors can also obtain the optimal efficiency.

An Intelligent Harmonic Synthesis Technique for Air-Gap Eccentricity Fault Diagnosis in Induction Motors

Induction motors （IMs） are commonly used in various industrial applications. To improve energy con- sumption efficiency, a reliable IM health condition moni- toring system is very useful to detect IM fault at its earliest stage to prevent operation degradation, and malfunction of IMs. An intelligent harmonic synthesis technique is pro- posed in this work to conduct incipient air-gap eccentricity fault detection in IMs. The fault harmonic series are syn- thesized to enhance fault features. Fault related local spectra are processed to derive fault indicators for IM air- gap eccentricity diagnosis. The effectiveness of the pro- posed harmonic synthesis technique is examined experi- mentally by IMs with static air-gap eccentricity and dynamic air-gap eccentricity states under different load conditions. Test results show that the developed harmonic synthesis technique can extract fault features effectively for initial IM air-gap eccentricity fault detection.

基于Ansys和Motor-CAD对交流伺服电动机性能的研究

基于某型号导弹发射装置电机的设计指标要求,运用Ansys有限元分析软件及Motor-CAD热分析软件分别进行性能优化分析,得出合理的设计方案。通过实测数据的验证得出:方案设计的准确率可达到93.5%以上,电机表面温升最大为19.2 K,与仿真值接近,方案设计合理。

Analysis of Capacitive Parasitism in PWM Inverter-Fed Motor

The effects of parasitic capacitance in induction motor system are unnoticed when it is fed from the AC line, but they are obvious when supplied directly from a PWM inverter. Consequently, many parasitic problems occur, such as motor to earth leakage current, bearing current, incoming line current distortion and uneven distribution of electrical stresses along the winding. On the basis of the uniform transmission line principle, a complete equivalent circuit of the PWM inverter fed motor system is presented, based on which all the capacitive parasitic problems mentioned above are analyzed and simulated by means of PSPICE. All the results are consistent with the existing ones.

Two-dimensional model of elastically coupled molecular motors

A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins. Extensive Langevin simulations of the model are performed. We discuss the dependences of motion and efficiency on the model parameters, including the external force and the temperature. A good qualitative agreement with the expected behavior is observed.

Outcomes in spasticity after repetitive transcranial magnetic and transcranial direct current stimulations

Non-invasive brain stimulations mainly consist of repetitive transcranial magnetic stimulation and transcranial direct current stimulation. Repetitive transcranial magnetic stimulation exhib- its satisfactory outcomes in improving multiple sclerosis, stroke, spinal cord injury and cerebral palsy-induced spasticity. By contrast, transcranial direct current stimulation has only been studied in post-stroke spasticity. To better validate the efficacy of non-invasive brain stimulations in im- proving the spasticity post-stroke, more prospective cohort studies involving large sample sizes are needed.