1,720,997 research outputs found
A DEVICE FOR HANDLING AND/OR PERFORMING WORK OPERATIONS ON OBJECTS
No full textA device for handling and/or performing work operations on objects comprises: at least a first arm (2) comprising a first end (2a) for supporting a tool (3) for picking or working; means for supporting and moving (4) the first arm (2); a first linear electric motor (5) connected to the first arm (2) for promoting a translation of the first arm (2) along a straight trajectory (X), preferably horizontal, and a second linear electric motor (6), associated to the first linear electric motor (5), developing along a closed path (P), which sets in rotation the first arm (2) about at least a circular trajectory (9)
Experimental Investigation of Shaft Radial Load Effect on Bearing Fault Signatures Detection
Full text linkThis paper investigates the influence of external radial load applied to the shaft on bearing fault detection based on vibration or current in induction motors operating under different conditions. This paper details the results of a laboratory trial comprising different test sets on the condition monitoring and fault diagnostic of a six-poles induction motor using a design of experiment (DOE) approach. The dedicated test setup comprises a custom-made fixture that allows us to dynamically vary the radial load applied to the output shaft. The aim is to investigate the effects of radial load on the fault diagnosis of shaft bearings and the interactions between other operating parameters, such as output torque. Specific scalar parameters have been proposed for the condition monitoring of the test motor from vibration and current data. The correct choice of the significant parameters is proven by the strong dependence on the damage returned by DOE results
Cross-Load Generalization of Bearing Fault Recognition with Decision Trees
No full textThe literature on condition monitoring is nowadays characterized by a wide variety of machine learning approaches. We argue that, in most of the works, the experimental evaluation is conducted in an oversimplified scenario, where training and test data contain samples obtained under the same radial and torsional load conditions. In this paper, we propose to apply an interpretable machine learning model, namely decision trees, to perform fault detection and recognition across different load configurations, a challenging benchmark that requires general-ization capabilities. The rules extracted from the trees provide explanations of the classification process
Detection of Generalized Roughness Bearing Fault by Spectral Kurtosis Energy by Vibration or Current Signals
No full textGeneralized roughness is the most common damage occurring to rolling bearing. It produces a frequency spreading of the characteristics fault frequencies, thus being difficult to detect with spectral or envelope analysis. A statistical analysis of typical bearing faults is here proposed in order to identify the spreading bandwidth related to specific conditions, relying on current or vibration measurements only. Then a diagnostic index based on the computation of the energy in the above defined bandwidth is used to diagnose bearing faults. The proposed method was validated experimentally with vibration signals, with robust and reliable results. The same procedure can be extended to current signals
Ground leakage current reduction in single-phase current source inverter topologies
No full textThis paper presents a grid-tied single phase photovoltaic microinverter based on Current Source Inverter (CSI) topology. The main topic of this work is related to the identification of a topology and a PWM strategy able to minimize the obvious issues of the basic CSI solution: efficiency and ground leakage current. The strong reduction of this last issue allows the use of the proposed solution in conjunction with Photovoltaic module in building integrated installations. Simulation results and a low voltage experimental validation present the effectiveness of the proposed solution in mitigating ground leakage currents
Active Rectifier With Integrated System Control for Microwind Power Systems
No full textThis paper presents simple and effective control strategies for the active rectifier stage (AC/DC stage) of a grid-connected low power system for micro wind applications employing Permanent Magnet Synchronous Generator (PMSG). In particular a novel algorithm for the estimation of the rotor angle of the PMSG, based on flux estimators, was implemented using an adaptive low-pass filter coupled with a feed-forward compensator. This enabled a very smooth start-up operation of the PMSG, obtained by pre-loading the values of the flux
estimator and using a single voltage transformer (VT) transducer. The solution for the power flow control between the active rectifier and the other(s) power converters connected to the common DC link was implemented without any digital communication between them, in order to obtain a solution suitable for modular architectures (e.g. to be used in conjunction with a grid-connected converter and/or an energy storage system). Simulation and experimental results confirmed the effectiveness of the proposed solutions. The experimental validation was conducted using a grid-connected converter as load for the proposed active rectifier
A design method to reduce pulsating torque in PM assisted synchronous reluctance machines with asymmetry of rotor barriers
No full textIn this paper a design method for ferrite assisted synchronous reluctance machine is proposed in order to reduce torque ripple and cogging torque. An asymmetrical layout of the rotor flux barriers is proposed in order to reduce the harmonics components of the pulsating torque. The proposed analytical method is validated, employing finite elements simulations, for pure synchronous reluctance (SyR) and permanent magnet assisted synchronous reluctance machines (PMSyR) considering different slot-pole configurations. Simulated machines present a cogging torque and a torque ripple reduction respectively up to 92% and up to 70%. Moreover the electromotive force waveform is improved too. These results are achieved without reducing nominal torque and without increasing machines production costs
Multi-stress lifetime model of the winding insulation of electrical machines
No full textIn this paper, a novel multi-stress model which estimates the lifetime of the winding insulation relative to its duty cycle is proposed and investigated. With an adequate implementation of this model, then an electrical machine can be designed not only in terms of its performance requirements, but also considering the associated reliability and lifetime aspects. The determination of the model parameters is based on the results of accelerated thermo-mechanical ageing tests
Power Losses Analysis in Interleaved Flyback Based PV Grid Connected Micro-Inverters
No full textThis paper analyzes the power losses of photovoltaic
micro-inverters based on flyback topology. A double
secondary winding flyback converter topology was considered
to inject alternating current into the grid. The purpose of this
work is the identification and quantification of the different power
losses present in a simple flyback topology and in the interleaved
version with two different control strategies. The power losses
comparison was carried out after designing a 250 W power
converter using commercial, low cost components. Simulations
in Matlab/Simulink environment highlighted the effectiveness of
the interleaved architecture
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