1,721,060 research outputs found
Monitoring of induction machines by maximum covariance method for frequency tracking
No full textMotor Current Signature Analysis (MCSA) has been widely investigated in order to monitor fault conditions of induction machines. On the other hand several solutions were proposed for the detection of rotor speed of induction motor for sensorless control. Another deeply investigated field of research is the detection of supply frequency of power lines, for the diagnosis of the distribution network. A common root of these three key topics is the need of accurately stating specific spectrum frequencies. Several techniques were presented in the literature in order to perform accurate tracking of frequencies for different purposes. They are modified versions of the traditional Discrete Fourier Transformation (DFT), or novel spectrum estimation techniques. This paper presents a novel procedure based on the statistical analysis of the current signal in the time domain, referred to as Maximum Covariance Method for Frequency Tracking (MCMFT), that allows to obtain high frequency resolution accuracy independently of the sampling frequency and of the time acquisition period. Therefore those spectrum lines related to supply frequency or to slip can be detected with extreme accuracy within a wide range of sampled data conditions. Then either an accurate diagnosis of the machine electric faults or sensorless control, or distribution network diagnosis can be performed. Comparison between the proposed method and the literature are reported, in order to critically analyze its performances. An induction machine with two artificially broken bars was used for the experiments
An experimental method to model electrical machines magnetic cores from the effective dynamic hysteresis loop: an application to switched reluctance motors
No full textPisa - Itali
SPICE aided analysis of UPS vector control
No full textThe possibility is studied of UPS (uninterruptible power supply) control based on the voltage vector referred to a rotating reference frame with velocity corresponding to voltage pulsation and on voltage pulsation itself. To verify the feasibility of the control strategy, a SPICE-aided simulation is reported. The numerical results show that, with asymmetrical load, a pulsation ripple is present owing to the nonsinusoidal voltage waveforms. Nevertheless, the computer harmonic distortion values are acceptable
Induction motor rotor quantities at load conditions: Finite Element analysis and experimental validation
No full textGeneration of low-EMI PWM patterns for induction motor drives with chaotic maps
No full textElectromagnetic radiation of power switches is an intrinsic characteristics of modern power conversion, since electronic converters adopt switching techniques, where the transistors are operated at very high frequencies, from a few kHz to some Mhz. The availability of reliable, fast and efficient power switches has spread the adoption of power inverters in many industrial applications. Among them drives for pump, high performance fan, heating systems, traction, are the most common areas of application. Recently, increasing attention has been focused on the emission of electromagnetic radiation of the converters which are commonly operated at fixed frequency at several amps, depending on the size of the motor. This results in a peak in the current spectrum at the switching frequency, which affects directly the emission of radiations and indirectly acoustic noise and mechanical vibrations. In this paper the design of chaos-based PWM (CB-PWM) for DC/AC converters for electric drives is investigated. The drive prototype will allow the experimental validation of EMI produced in a shielded or anechoic room, and the evaluation of drive performances, from the point of view of torque ripple and efficiency. From theoretical analysis and experiments it is shown that a reduction of the peak emission around the switching frequency up to 20 dB, without affecting performances
SPICE assisted simulation of controlled electric drives: An application to switched reluctance drives
No full textAn example of the simulation of a closed loop controlled electric drive that shows the feasibility of simulating this equipment by means of a general-purpose electronic circuit analysis program is described. A SPICE program is used owing to its well-known facility for simulating electronic circuits. Its application to the control of a switched reluctance drive is presented. A way to extend SPICE to the simulation of the electromechanical energy conversion and the drive control is also presented. A closed-loop speed control is considered, and the simulation results are validated by experimental tests executed on an industrial drive
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