Finite element modelling of nonlinear stress grading materials for machine end windings

Baker, A.E.; Gully, A.M.; Wheeler, J.C.G.

doi:10.1049/cp:20020126

Cited by 15 publications

(6 citation statements)

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“…A useful tool in FEM modeling is the ability of reducing the dimension of the elements used to discretize the stress-grading coating subdomain [29]. These coatings are applied in thin layers that require a very fine element discretization; otherwise, if a coarse discretization of the subdomains is used, numerical instability may result [47]. Assuming that the conductivity of the semi-conductive coating depends only on the tangential component of the electric field, the elements used in the SG coatings can be reduced to one dimension (1D) [48].…”

Section: Finite-element Dimension Reduction On the Stress-grading Coamentioning

confidence: 99%

Modeling and Simulation of Rotating Machine Windings Fed by High-Power Frequency Converters for Insulation Design

Cortés¹,

Gómez²,

KhalilHussain³

2018

Simulation and Modelling of Electrical Insulation Weaknesses in Electrical Equipment

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Modern power systems include a considerable amount of power electronic converters related to the introduction of renewable energy sources, high-voltage direct current (HVDC) systems, adjustable speed drives, and so on. These components introduce repetitive pulses generated by the commutation of semiconductor switches, resulting in overvoltages with very steep fronts and high dielectric stresses. This phenomenon is one of the main causes of accelerated insulation aging of motors in power electronic-based systems. This chapter presents state-of-the-art computational tools for the analysis of motor windings excited by fast-front pulses related to the use of frequency converters based on pulsewidth modulation (PWM). These tools can be applied for the accurate prediction of overvoltages and dielectric stresses required to propose insulation design improvements. In the case of the stress-grading system used in medium-voltage (MV) motors, transient finite-element method (FEM) is used to study the effect of fast pulses. It is shown how, by controlling the material properties and the design of the stress-grading systems, solutions to reduce the adverse effects of fast pulses from PWM-type inverters can be proposed.

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Section: Finite-element Dimension Reduction On the Stress-grading Coamentioning

confidence: 99%

Modeling and Simulation of Rotating Machine Windings Fed by High-Power Frequency Converters for Insulation Design

Cortés¹,

Gómez²,

KhalilHussain³

2018

Simulation and Modelling of Electrical Insulation Weaknesses in Electrical Equipment

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“…The elementary parts of the stress-grading layer may have monitored properties. Unfortunately, the geometry of the stress-grading, and in particular its thickness, leads to programming problems using the finite elements method [47,48]. Practically, designers want to know the highest value of the electrical field, the thermal hot spot location, the expected leakage current.…”

Section: Main Insulation In the End Winding Area Criteria And Issuementioning

confidence: 99%

“…The solving times will be too high. Some authors suggest simplifications in solving [47]. Thereafter, 2D simulations can provide enough information to study the stress-grading layer effect.…”

Section: Main Insulation In the End Winding Area Criteria And Issuementioning

confidence: 99%

The Insulation for Machines Having a High Lifespan Expectancy, Design, Tests and Acceptance Criteria Issues

Barré¹,

Napame²

2017

Machines

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Abstract:The windings insulation of electrical machines will remain a topic that is updated frequently. The criteria severity requested by the electrical machine applications increases continuously. Manufacturers and designers are always confronted with new requirements or new criteria with enhanced performances. The most problematic requirements that will be investigated here are the extremely long lifespan coupled to critical operating conditions (overload, supply grid instabilities, and critical operating environments). Increasing lifespan does not have a considerable benefit because the purchasing price of usual machines has to be compared to the purchasing price and maintenance price of long lifespan machines. A machine having a 40-year lifespan will cost more than twice the usual price of a 20-year lifetime machine. Systems which need a long lifetime are systems which are crucial for a country, and those for which outage costs are exorbitant. Nuclear power stations are such systems. It is certain that the used technologies have evolved since the first nuclear power plant, but they cannot evolve as quickly as in other sectors of activities. No-one wants to use an immature technology in such power plants. Even if the electrical machines have exceeded 100 years of age, their improvements are linked to a patient and continuous work. Nowadays, the windings insulation systems have a well-established structure, especially high voltage windings. Unfortunately, a high life span is not only linked to this result. Several manufacturers' improvements induced by many years of experiment have led to the writing of standards that help the customers and the manufacturers to regularly enhance the insulation specifications or qualifications. Hence, in this publication, the authors will give a step by step exhaustive review of one insulation layout and will take time to give a detailed report on the standards that are linked to insulation systems. No standard can provide insurance about lifespan, nor do any insulation tests incorporate all of the operating conditions: thermal, mechanical, moisture and chemical. Even if one manufacturer uses the standards compliance to demonstrate the quality of its realization; in the end, the successful use in operation remains an objective test. Thereafter, both customer and manufacturers will use the standards while knowing that such documents cannot fully satisfy their wishes. In one 20-year historical review, the authors will highlight the duration in insulation improvements and small breakthroughs in standards writing. High lifespan machines are not the main interest of standards. A large part of this publication is dedicated to the improvements of the insulation wall to achieve the lifespan. Even if the choice of raw materials is fundamental, the understanding of ageing phenomena also leads to improvements.

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“…Finite element method is the powerful tool for analyzing complex electromagnetic phenomena in the media. In the past study on the FEM simulation of dielectrics, all of them used macrostructure for analysis of the electric field distribution inside [2][3]. However, the simulation of dielectric properties of composite material using FEM in mesoscopic is rarely reported.…”

Section: K-4mentioning

confidence: 99%

Mesoscopic FEM simulation of dielectric properties of composite material and experimental verification

Huang

Samee

et al. 2009

2009 IEEE 9th International Conference on the Properties and Applications of Dielectric Materials

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Composite material technology has a great potential for development of new insulating materials. By use of computer simulation method to study the dielectric properties of composite material can save a lot of time and material resources. In this paper we have studied the dielectric properties of electric field grading non-linear composites through computer simulation and verified them with experimental studies. For inorganic filler, a mesoscopic scale computer simulation method which uses finite element technique is used to study dielectric properties After transient FEM simulation under AC voltage, Least-squares method is adopted to decompose the total current into resistive current and capacitive current according to applied macro-field strength. The simulation results are in agreement with experimental results.

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Finite element modelling of nonlinear stress grading materials for machine end windings

Cited by 15 publications

References 0 publications

Modeling and Simulation of Rotating Machine Windings Fed by High-Power Frequency Converters for Insulation Design

Modeling and Simulation of Rotating Machine Windings Fed by High-Power Frequency Converters for Insulation Design

The Insulation for Machines Having a High Lifespan Expectancy, Design, Tests and Acceptance Criteria Issues

Mesoscopic FEM simulation of dielectric properties of composite material and experimental verification

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