Claudia Martis

An equivalent internal circuit of the induction machine for advanced spectral analysis

The aim of this paper is to develop a method to validate an equivalent internal circuit of the three-phase squirrel-cage induction machine for advanced signal processing including fault diagnosis. The proposed method is based on the computation of the stator and rotor current spectra. An experimental setup for an 11-kW induction machine was developed in order to get numerical data for voltages and currents from the stator side. The comparison between the analytical computation, the simulation, and the experimental results, shows the model capability to reproduce the electromagnetic phenomena in the induction machine with mixed time and space harmonics. The proposed model can be used to design electrical fault detection devices with low cost and noninvasive sensors.

Induction Machine Broken Bars Fault Detection Using Stray Flux after Supply Disconnection

The aim of this paper is to present a new approach to detect broken bars fault in squirrel-cage induction machine. This approach is based on the study of stray flux signal after the supply disconnection. This type of test is useful especially for the maintenance purpose when it is possible to remove the load and supply effects. In this case, the current in rotor side decrease by its time constant and the spectrum induced in a search coil around the induction machine is analyzed with a time-frequency method allowing the rotor faults detection. The broken rotor bar effect is analyzed in the induced stator voltage spectrum too, but the experimental results show that its sensitivity is weak with respect to the given by the search coil induced voltage spectrum

Comparative study of different torque sharing functions for losses minimization in Switched Reluctance Motors used in electric vehicles propulsion

In this paper the authors present a comparison between optimised versions of three torque sharing functions, with different number of degrees of freedom, used for improving the efficiency in Switched Reluctance Motors. Starting from the basic rectangular variation, the ascending and descending flanks of the function are modeled using a cosine, exponential and a more general approach (further referred to as piecewise cubic sharing function). The degrees of freedom varying between two and an arbitrary number (for the general approach) are determined so as to minimize losses, when operating in smooth torque conditions. Based upon an optimisation procedure with both linear and nonlinear constraints, the total (copper and iron) losses are minimized considering a limited available DC bus voltage. Moreover, a smooth model is presented so as to be able to separate the two main causes for the torque ripple and it is shown that, neglecting the chopping ripple, a ripple-free torque can be obtained. Extensive studies have been conducted for determining the optimal number of degrees of freedom (DoFs) for the piecewise cubic function. The proposed methods were successfully implemented on a 8/6, 30kW peak power, SRM both numerically and experimentally-wise.

Electrical Machines Virtual Laboratory: Grid Connection of a Synchronous Generator

Virtual laboratories can become important components of the teaching process, because using them several experiment-oriented problems can be solved easily and also from the distance. Graduates using virtual laboratories will be better trained when they enter the job market. In the paper a laboratory work will be presented having two components: a simulation and an experimental module. Both can be used for the preparation of a real lab and for accessing the real-world experiments. The virtual lab modules can also allow multiple students to remote access the experiments, the multicast data transfer mechanisms and arbitration mechanisms

Fault tolerant permanent magnet synchronous machine for electric power steering systems

Multiphase motor drives posses many advantages over the traditional three-phase motor drives such as reducing the amplitude and increasing the frequency of torque pulsation, reducing the stator current per phase without increasing the voltage per phase, lowering the dc link current harmonics and higher reliability. By increasing the number of phases it is also possible to increase the torque per ampere for the same volume and improving the fault tolerance of the drive. The present paper approaches in a comparative manner two winding connection for a 12 stator slots/10 rotor pole permanent magnet synchronous machine. The magnetic filed and developed electromagnetic torque will be analyzed.

Harmonic characteristics of an induction machine connected to a distribution network

This paper presents a complete study of the induction machine allowing the determination of its harmonic characteristics generated in the line current. The method used to analyse the induction machine behaviour is based on the circuit-oriented approach. The developed model facilitates the estimation of frequencies and maximum values of the stator current harmonic components. Using the EMTP/ATP electrical network simulation package, the obtained circuit-oriented model is simulated in normal conditions at the rated load and the results are compared with theoretical results and experimental measurements.

Switched reluctance motor analytical models, comparative analysis

Two categories of analytical models developed for switched reluctance motor (SRM) are discussed in the paper. The models are based on motor geometry data and respectively on finite element method (FEM) analysis results. For an existing and tested sample SRM the flux linkage and the torque characteristics were calculated via all considered models and the results were compared with the FEM analysis based calculated characteristics. Finally the merits and the weak points of each model were evinced.

Design and testing of a four-sided permanent magnet linear generator prototype

In the perspective of the fossil fuels deposits depletion new energy resources must be developed; amongst them the renewable energy sector seems to be able to provide a long term solution. Besides the already popular wind, solar or thermal energies, the ocean energy sector offers a virtually infinite energy potential; many solutions for harvesting and converting this energy into usable form are under investigation, most of them using complex mechanical or hydraulic systems to convert the slow, linear movement specific to waves into rotational movement, compatible with the classical electric generators. Our focus is on systems using linear electric generators, offering higher efficiency and reliability, the present paper presenting the stages covered to choosing, designing, building and testing a linear generator.

Comparative analysis of different synchronous reluctance motor topologies

Synchronous reluctance machines become more popular nowadays. Development of power electronics allowed reluctance motors to be used in many drive applications. Due to increased interest in electric vehicles and high prices of PMs, the research on electric drives is mainly focused on reluctance machines. Lack of rotor winding lowers copper losses, simplifies power supply system and increases machines robustness. SynRM produces torque due to rotors magnetic anisotropy, which is achieved in machines with transversally laminated rotor by introducing flux barriers. The main goal when designing rotors flux barriers is to achieve the highest saliency ratio possible. However, since operation of the machine depends on interaction between stator magnetic field and the rotor, both stator and rotors topologies should be taken into account when designing the machine. This paper presents a comparison of SynRMs with stators of three different slot numbers and two different rotors topologies.

Permanent magnet linear generator for renewable energy applications: Tubular vs. four-sided structures

While the exhaustion of carbon based fuels has become a certitude, the use of alternative fuels became more popular in the last decades. The renewable energy sector emerged, providing an alternative to conventional energies; amongst them the wind and solar energies became extremely popular in the last decades, supplying important parts of the total energy required in countries like Germany or the United States of America. Besides these, the wave energy sector represents a huge, yet unexploited domain, which could prove to be a long time solution for the forthcoming energy shortages.