Search results

When magnetic saturation in ac machines is evolved, the theory of main flux saturation in d-q axes remains the best. Because of its simplicity, it is the most used in either motoring or generating mode for synchronous or asynchronous machines. Although, it is considered as a global way of introducing the iron saturation, compared to other methods, today, its fidelity has no contest in predicting complex ac machine operations. For this purpose, the aims of this paper consists of modeling these machines whatever the state-space variables values are taking into account the magnetic saturation. Two unified procedures are proposed. The first one deals with a common approach to establishing a complete and detailed model synthesis in d-q axes. The second also presents a unified approach to introducing magnetic saturation of the iron core in the characteristic equations. The analysis takes the salient pole synchronous machine as a general case of study. Then the approaches are extended to undamped and smooth air gap synchronous machines as well as induction machines. The paper aims to discuss these issues.

The present paper, which is a first part of a work under study dealing with a unified method to derive multiple models of saturated ac machines, is intended to the description of an alternative method and its application for induction and synchronous machines. It mainly consists of the following parts: first, after writing the stator and rotor space vector d-q equations, the number of possible models is immediately discussed. By considering the currents and fluxes as state-space variables, 14 models are obtained for AC induction machine (IM and SM). They are classified into three families, current (three), flux (three) and mixed models (eight). Second, in order to easily introduce the magnetic saturation in the 14 developed models, a method is presented. It consists of just elaborating the model with the winding currents as state variables, then deriving all the other models from it. Third, to emphasize the influence of the presence of magnetic saturation, in each model, each inductance along the d and q axes is written with a fundamental expression which exists with or without saturation and an additional one due purely to saturation. Hence the additional terms can be studied and quantified in an easy way or simply removed when linear case is assumed. Fourth, adopting such strategy to write the different coefficients of the models had led to the definition of common saturation factors. In turn, the definition of common saturation factors had allowed the definition of different groups of models within each family. Fifth, an alternative to evaluate the static and dynamic saturation coefficients is also proposed. It is shown that by proper fitting of the experimental magnetizing curve, all saturation coefficients can be written only in terms of which is simply the magnitudes ratio of the magnetizing flux and current. Sixth, although the theory of the main flux saturation is now admitted, an investigation was carried out on a self-excited induction generator and the build-up of voltage and current phases of a standalone alternator, to prove the equivalence between the all developed models.

The number of models based on the state-space variables choice, of a saturated ac machine, is reviewed. A simple method consisting of elaborating just the winding currents model, with magnetic saturation and deriving all the other models from it, is presented. In this study special interest was particularly focussed on either novel models or existing models cited in the literature but cannot be obtained by other approaches. In all cases, if the differential equations of the machine are formulated in terms of a set of variables other than the winding currents, a noticeable reduction in the size of equations may be obtained and consequently less time computing. The approach seems to be able to derive any possible model whatever the state-space variables and the type of the ac machine and hence can be classified as a general approach.

The experiments of synchronous and induction machine transients prove the validity of the method.

By suitable choice of state-space characteristic vectors among the fluxes and the currents, a synthesis of AC machine models in d-q axes is established. To introduce magnetic saturation in each model, an approach-based uniquely on the elaboration of the winding currents model is exposed and applied. In addition, the analysis gives a detailed classification of all found models taking into account the state variables nature as well as the cross-coupling coefficient considered as a saturation factor. The study is completed with a simple alternative to evaluate all saturation factors by just calculating the static magnetizing inductance.

In order to assess the performance of an induction generator in standalone wind power application, it is imperative that mathematical models are developed that accurately represent the system and take into account various electromagnetic influences such as skin effect. The purpose of this paper is to utilize mathematical models to study the transient and steady‐state behaviour of the self‐excited induction generator (SEIG), in one case with an aluminum rotor, in another case, with a copper rotor, under various load conditions while taking the above factor into account.

Mathematical models of a SEIG in the d‐q axis frame have been developed based on the generalized machine theory. A relationship between the mutual inductance and the magnetizing current of the machine has been presented. The rotor impedances have been customized to include skin effect. Using these relations, the model has been extended to include the saturation and skin effects. In order to verify the accuracy of the models, numerical and experimental investigations have been carried out on two 7.5 hp aluminum‐rotor and copper‐rotor SEIGs.

It was found that the model that takes into account the saturation and skin effects produces numerical results that closely match experimental values for both the machines.

This paper describes how a model of an SEIG considering saturation and skin effect has been developed and applied to aluminum‐ and copper‐rotor machines of similar power ratings to analyze their performance.

This paper aims to use a scaling approach to scale the solutions of a beforehand-simulated finite element (FE) solution of an induction machine (IM). The scaling procedure is coupled to an analytic three-node-lumped parameter thermal network (LPTN) model enabling the possibility to adjust the machine losses in the simulation to the actual calculated temperature.

The proposed scaling procedure of IMs allows the possibility to scale the solutions, particularly the losses, of a beforehand-performed FE simulation owing to temperature changes and therefore enables the possibility of a very general multiphysics approach by coupling the FE simulation results of the IM to a thermal model in a very fast and efficient way. The thermal capacities and resistances of the three-node thermal network model are parameterized by analytical formulations and an optimization procedure. For the parameterization of the model, temperature measurements of the IM operated in the 30-min short-time mode are used.

This approach allows an efficient calculation of the machine temperature under consideration of temperature-dependent losses. Using the proposed scaling procedure, the time to simulate the thermal behavior of an IM in a continuous operation mode is less than 5 s. The scaling procedure of IMs enables a rapid calculation of the thermal behavior using FE simulation data.

The approach uses a scaling procedure for the FE solutions of IMs, which results in the possibility to weakly couple a finite element method model and a LPTN model in a very efficient way.

Modeling electric machines is one of the powerful approaches for analyzing their performance. A dynamic model and a steady-state model are introduced for each electric machine. Permanent magnet induction machine (PMIM) is a dual-rotor electric machine, which has various advantages such as high-power factor and low magnetizing current. Studying PMIM and its modeling might be valuable. The purpose of this paper is to introduce a simple and accurate method for dynamic and steady-state modeling of PMIM.

In this paper, arbitrary dqo reference frame is used to model PMIM. First, three-phase dynamic equations of stator and rotors are introduced. Then, they are transferred to an arbitrary reference frame. The voltage and magnetic flux equations aligned at dqo axes are obtained. These equations give the dynamic model. To investigate the results, PMIM simulation is performed according to obtained dynamic equations. Simulation results verify the analytic calculations.

In this paper, dynamic equations of PMIM are obtained. These equations are used to determine dynamic equivalent circuits of PMIM. Steady-state equations and one phase equivalent circuit of the PMIM using phasor relations are also extracted.

PMIM equations along dqo axes and their dynamic and steady-state equivalent circuits are determined. These equations and the equivalent circuits can be transformed to different reference frames and analyzed easily.

The purpose of this paper is to study the development of novel multiphase induction motor (MPIM) with copper die cast rotor in the drive system of electric propulsion vehicles (EPV). It is estimated that the manufacturers are concerned about high torque,Efficiency, motor life, energy conservation and high thermal tolerance. To ensure maximum torque and efficiency with multiphase winding and copper die cast technology to increasing high thermal tolerance, life, energy conversations. On other hand, it is very important of EPV application.

The focus of the investigation is threefold: the modified method carried out on MPIM both stator and rotor can overcome the current scenario problem facing by electric vehicles manufacture and developed perfect suitable electric motor for EPV applications. The design and simulation carried out finite element method (FEM) that was more accurate calculations. Finally developed prototype model of MPIM with copper die cast are discussed with conventional three phase Die casting Induction motor.

The paper confirmed the multiphase copper die-cast rotor induction motor (MDCrIM) is providing better performance than conventional motor. Proposed motor can bring additional advantage like heat tolerances, long life and energy conversations.

The experiments confirmed the MDCIM suitable for EPV Applications. The modified MDCIM of both stator and rotor are giving better result and good performance compared to conventional method.

Induction machines for traction applications are operated at working points of high ferromagnetic saturation. Depending on the working point, a broad spectrum of harmonic frequencies appears in the magnetic flux density of induction machines. Detailed loss analysis therefore requires local and temporal highly resolved nonlinear field computation. This loss analysis can be performed in the post processing of nonlinear transient finite element simulations of the magnetic circuit. However, it takes a large number of transient simulation time steps to build up the rotor flux of the machine.

In this paper, hybrid simulation approaches that couple static FEA, transient FEA and analytic formulations to significantly decrease the number of simulation time steps to calculate the magnetic field in steady state are discussed, analyzed and compared.

The proposed hybrid simulation approaches drastically decrease the simulation time by shortening the transient build-up of the rotor flux. Depending on the maximum error of the rotor flux linkage amplitude compared to the steady state value, a reduction of simulation time steps in the range of 55.5 to 98 per cent is found.

The presented hybrid simulation approaches allow efficient performing of the transient FE magnetic field simulations of induction machines operated as traction drives.

To present results of research closely linked to real life applications and to resume the work of a period of a few years.

The combination of finite‐element method (FEM) and boundary‐element method is applied to simulate the electromagnetic, mechanical, and acoustic behaviour of an induction machine with squirrel‐cage rotor. The paper gives an overall view of the workflow and the implemented mathematics, starting off with the two‐dimensional, transient electromagnetic simulation and the succeeding three‐dimensional, static electromagnetic simulation. Theory and results of the mechanical and acoustic simulations are discussed.

A main result of the research work is that the simulation of the acoustic behaviour of an electrical machine is very time‐consuming. Furthermore, geometry adoption, especially of the mechanical model, is very sensible.

Using the FEM for simulation of structure dynamic problems is often limited to how the boundary layers are handled. In real life materials are not “connected” but glued or clamped. Therefore, the behaviour can only be adapted by manipulating the material parameters. There are other methods known for simulation, which could be applied. On the other hand, measurements could be used for iterative parameter adoption.

A significant result of the work is that the results obtained only allow for comparison. Exactness is more a question of modelling the real behaviour than matching the results to measurement in terms of values.

This paper gives an overview of how to simulate the complete chain from electromagnetics to acoustics of an electric machine.

Based on Fourier series theory, for almost periodic functions, the general as well as the specific harmonic‐balance model of induction machines is presented together with a brief derivation. Whereas the general model refers to both symmetrical and asymmetrical machines, the specific one is valid for only the former ones, with windings without parallel branches. The specific model permits classification of all symmetrical machines into three categories. The classification preserves its usefulness for machines not strictly fulfilling assumptions for the validity of the specific model. Expressions for the asynchronous and synchronous torque components are derived. Categories as well as frequencies of both the slot harmonics and the synchronous torques are listed in four tables referring to machines with one to four pole pairs.

Seeks to posit a new procedure to optimize the geometry of an electric motor for hybrid vehicles (HV), based on an optimization model implementing the complex specifications, environment‐sizing constraints and vehicle‐operating points.

In this work, induction machines (IM) were studied for automotive traction applications, more specifically, for HV. The necessary models and methods to analyse and design such electric machines were developed. A limited number of finite element computations was used to establish a non‐linear electromagnetic model of the machine. This model was then adapted to study the sensitivity of the design for the most significant geometric variations. Thus, one can easily adapt a machine for new sizing requirements.

This modelling methodology was extended to take into account a great number of parametric variations. This model was used for constrained optimisation on the geometry of a machine. To achieve this, a new “reset model optimisation” method was proposed, combining fast computations, precision and simplicity. This methodology was used to design an IM with HV‐sizing considerations.

The methodology is based on an improved equivalent circuit of the IM where the FEM accuracy (saturation) is combined with the potential of analytical modelling (simple and quick).

This half‐analytical, half‐FEM methodology is well adapted for research projects where the specifications are frequently reviewed.

The purpose of this paper is to present analysis of an influence of rotor slots opening on self-excitation process, terminal voltage and performance characteristics of the single-phase self-excited induction generator (SPSEIG).

The paper presents field analysis of the self-excitation problem in the SPSEIG and performance characteristics on the base of two-dimensional field-circuit model of the generator.

The carried out field computations of the tested SPSEIG with closed rotor slots showed that only an initial voltage across the excitation capacitor of about nominal value (230 V) causes successful self-excitation of the generator. It was also proved that the suitable opening of the rotor slots, beside remnant flux density in the rotor core, facilitates self-excitation in the generator. Since in working applications initially charging of the capacitor to almost nominal voltage may cause a problem, therefore employment of semi-closed rotor slots in the SPSEIG would be proper solution.

The conducted simulations, validated by laboratory tests showed that not only suitable excitation capacitor capacitance and rotor speed are needed to obtain desired terminal voltage of the generator, but also suitable initial voltage across the capacitor in auxiliary stator winding is very important and necessary for reliable self-excitation of the single-phase induction generator with closed rotor slots. The employment of semi-closed rotor slots in the SPSEIG makes the self-excitation more effective.