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The purpose of this paper is to carry out an analytical approximation model (heat transfer model (HTM)) for the calculation of the heat transfer coefficient at the end winding bars of large hydro generators. These coefficients are needed for lumped parameter thermal models in the design process.

The computational fluid dynamics simulation in combination with conjugate heat transfer (CHT) validates the accuracy of the HTM. The theoretical approach describes the formulation of the heat transfer coefficient and the Gauss-Newton method has been applied to find the coefficients of the approximation model.

The paper describes the new analytical approximation model for the heat transfer coefficient at the end winding bars of hydro generators and shows also the validation to simulation results.

The analytical approximation model for the heat transfer coefficient at the end winding bars has been described and a comparison with CHT results has shown a good agreement.

The purpose of this paper is to present a new computational fluid dynamics model for large electrical machines to simulate the heat transfer at specific components to the appropriate ventilation method. The most damageable parts for overheating in generators are the end winding bars, pole windings and stator ducts.

The reduced model introduced is basically derived from the state-of-the-art pole section model (PSM) and enables faster computations for heat transfer and cooling simulations of electrical machines. The fundamentals of the two methods and the grid generation are described. Two PSMs and four different reduced models are presented and compared among each other to tune the reduced model.

As a topic of outstanding interest in large hydro generators, the heat transfer at the end winding bars is solved with the aid of the reduced model. This slot sector model (SSM) has been validated and the computation time has been reduced enormously in comparison to the state-of-the-art PSM.

The heat transfer has been carried out only for the end winding region of large hydro generators. The effect of the reduced model on the pole sections and stator ducts has not been investigated. Nevertheless, the reduced model is also valid for large motors.

This reduced model can finally be used for parametric studies with different cooling schemes and boundary conditions in the design process.

The comparison of various SSMs to PSMs shows an acceptable accuracy of the reduced model in combination with a rather low computation time. Due to modeling one slot only, the MFR-MP approach is an adequate and fast analyzing method for this kind of model structure.

The end winding current distribution of the squirrel cage rotor consists of (Fig.1) : a peripheral current flowing in the end ring of the cage placed at a distance ar from the end core plane, 2) an axial current flowing in the straight part of the

The calculation of the end winding leakage of a squirrel‐cage induction motor using a three‐dimensional finite element method is discussed. The end winding inductance is thought to consist of a leakage, describing the flux linked with the end winding only, and a mutual part, describing the flux linked with both end winding and end ring. Both leakage and mutual inductance are found to vary for different load conditions.

Discusses the 27 papers in ISEF 1999 Proceedings on the subject of electromagnetisms. States the groups of papers cover such subjects within the discipline as: induction machines; reluctance motors; PM motors; transformers and reactors; and special problems and applications. Debates all of these in great detail and itemizes each with greater in‐depth discussion of the various technical applications and areas. Concludes that the recommendations made should be adhered to.

Problems caused by end winding vibrations in power plant generators have become increasingly evident in recent years and reveal a need for monitoring and diagnostic systems. An increasing number of operational outages are caused by failures of the winding insulation or the conductor itself due to end winding vibrations. Meanwhile, it is clear that the condition of the end winding must be continuously monitored during operation to detect ineffective end winding support in time and to plan the repair.

In this paper, the complex and nonlinear excitation mechanisms in large machines are presented and modern methods for vibration monitoring are described. Through a consistent use of vibration monitoring in the end winding area as well as the vibration diagnosis done by experts, damage mechanisms can be detected at an early stage, repair measures can be planned and serious damage owing to a weakened main insulation can be avoided.

By combining modal analysis and trend monitoring in relation to the learned vibration behaviour, the end winding condition can be assessed in a differentiated manner and changes in the end winding structure can be detected early.

Finally, an assessment for a two-pole, air-cooled turbo generator is proposed.

The purpose of this paper is to introduce an analytic method to calculate the slot leakage reactance of stator bar strands in alternative current machines whose stator windings have multiple bars per layer and using deficient transposition.

Based on the analysis of deficient transposition, the calculation model of mutual slot leakage reactance between any two strands in one bar is established. The subsection integral method is presented to calculate the slot leakage reactance and analytic function is listed. A pump motor used in nuclear power is taken as an example, and the slot self leakage reactance of any strand in its top layer winding and the slot mutual leakage reactance between one strand and other strands in the same bar are calculated depending on the method described above. The slot leakage reactance of all strands in the top layer winding is calculated when different transposition angles are applied in stator bars.

The results show that subsection integral method is effective in calculating the slot leakage reactance of stator bar strands of deficient transposition. The slot leakage reactance distribution of all strands is obtained. The transposition angle has a great impact on the slot leakage reactance distribution of stator bar strands.

This paper presents an available method to calculate the slot leakage reactance of any strands in alternative current machine whose stator windings have multiple bars per layer and using deficient transposition, and discusses the impact of transposition angle on the slot leakage reactance. The conclusion can lay the foundation of the effective calculation of circulating current losses in stator bars with deficient transposition.

The purpose of the paper is to investigate the performance of induction machines with fractional‐slot concentrated‐windings.

This paper examines induction machine performance with fractional‐slot concentrated windings using the standard distributed lap windings as reference. Four designs are compared and various performance tradeoffs highlighted. The first machine has integral‐slot distributed 2 slots/pole/phase lap winding and it serves as the reference winding. The second machine has a double‐layer 1/2 slot/pole/phase winding, a workhorse for brushless DC machines. The third machine has double‐layer 2/5 slot/pole/phase winding. Lastly, the fourth machine has single‐layer 2/5 slot/pole/phase windings. The comparison includes torque‐speed curves (including the effects of major space harmonic components), rotor bar losses, and ripple torque levels.

Based on the analysis results presented here, the traditional distributed lap winding is proven to be superior to FSCW in terms of torque production and rotor bar losses for induction machine applications. The 1/2 spp shows some promising results in terms of torque production, in addition to significant reduction and simplification of end turns with lower number of coils albeit with more turns/coil (12 slots vs 48 slots). The penalty is the additional rotor bar losses due to the 2nd and 4th harmonic mmf components. The 2/5 spp is not promising for torque production and should be avoided. The transient simulation results that simultaneously take into account the effects of all space harmonics and magnetic saturation showed comparable trends compared to the harmonic analysis results. It has also been shown that FSCW tend to have higher torque ripple compared to distributed windings.

To the best of the authors' knowledge, this paper for the first time attempts to quantitatively address the tradeoffs involved in using FSCW in induction machines.

This paper aims to give a perspective about the variety of techniques which are available and are being further developed in the area of coupled field formulations, with selective bibliography and practical examples, to help postgraduate students, researchers and designers working in design or analysis of electrical machinery.

This paper reviews the recent trends in coupled field formulations. The use of these formulations for designing and non‐destructive testing of electrical machinery is described, followed by their classifications, solutions and applications. Their advantages and shortcomings are discussed.

The paper gives an overview of research, development and applications of coupled field formulations for electrical machinery based on more than 160 references. All landmark papers are classified. Practical engineering case studies are given which illustrate wide applicability of coupled field formulations.

Problems which continue to pose challenges to researchers are enumerated and the advantages of using the coupled‐field formulation are pointed out.

This paper gives a detailed description of the application of the coupled field formulation method to the analysis of problems that are present in different electrical machines. Examples of analysis of generators and transformers with this formulation are presented. The application examples give guidelines for its use in other analyses.

The coupled‐field formulation is used in the analysis of rotational machines and transformers where reference data are available and comparisons with other methods are performed and the advantages are justified. This paper serves as a guide for the ongoing research on coupled problems in electrical machinery.

The purpose of the paper is to present an analysis of an influence of shape and material of rotor bars on the process of self-excitation and performance characteristics of single-phase, self-excited induction generator (SP-SEIG).

The presented analysis is based on the results of transient simulations of SP-SEIG performed with the use of field-circuit model of the machine. Four various shapes of the rotor bars and two different conductor materials were investigated. The results for the base model with rounded trapezoidal rotor slots were validated by measurements.

An improvement of the performance characteristics – the extension of the stable operating range of the generator – was obtained for rectangular copper rotor bars. The improvement is the result of strong skin effect in the squirrel rotor cage. Application of round rotor slots results in shorter time of voltage build-up during the self-excitation of the generator caused by less apparent deep bar effect in round bars.

The originality of the paper is the application of the copper rotor cage in the single-phase, self-excited induction generator. Its use is beneficial, as it allows for extension of the range of stable operating range. The results may be used for designing new constructions of the single-phase, self-excited induction generators, as well as the constructions based on general purpose single-phase induction motors.