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The purpose of this paper is to introduce an efficient model for analysis of the voltage distribution along the long ceramic insulator strings in a high‐voltage tower window, especially when the structure and parameters of the ceramic insulator are unknown. The effect of the grading ring on the voltage distribution is also investigated.

A circuit model composed of capacitors is used to analyze the voltage distribution along the ceramic insulator strings in a transmission tower window. The capacitances of the disk insulators, line conductors, and tower are obtained by using the finite element method, charge simulation method, boundary element method, and measurement according to their characteristics.

The model is very efficient. The voltage distribution along insulator strings can be optimized by adjusting the parameters of the grading ring. The maximum amount of voltage applied to a single insulator disk can be reduced effectively by increasing either the diameter of the grading ring or the distance from the upper surface of the grading ring to the high‐voltage end of the insulator string.

The model is very efficient for analysis of the voltage distribution along the long ceramic insulator strings, especially when the structure and parameters of the ceramic insulator are unknown.

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.

The thermal management of electrical insulations poses a challenge in electrical devices as electrical insulators are also thermal insulators. Diamond is the best solid electrical insulator and thermal conductor. This can lead to a paradigm change for electrical machine winding and lamination insulation design and thermal management. The paper introduces these techniques and discusses its effect for the design of electrical machines and its potential consequences for electromagnetic analysis, for example, in multi-physics modelling. The diamond winding insulation is patent-pending, but the diamond enriched lamination insulation is published for the benefit of the scientific community.

The windings of electrical machines are insulated to avoid contact between the coil and other conductive components, for example, the stator core. The principle of using mica tape and resin impregnation has not changed for a century and is well established to produce main insulation on a complex conductor shape and size. These insulations have poor heat-conducting properties. Similarly, the insulation of laminated steel sheets comprising the stator and rotor restrict heat flow. Diamond-based insulation provides a new path. Increased thermal conductivity means reduced temperature rise and the reduced thermal time constants in multi-physics simulations and system analysis.

The largest benefit of a diamond-based core insulation is in electrical machines in which the losses are conducted axially to the coolant. These are machines with radial ducts and effective cooling in the end regions. The main benefit will be in reducing the number of radial ducts that positively affect the size, production costs and the copper losses of the machine. The increased thermal conductivity of the diamond insulation system will reduce the thermal constants noticeably. These will affect system behavior and the corresponding simulation methods.

Diamond insulation can lead to a paradigm change for electrical machine winding and lamination insulation design and thermal management. It might also lead to new modeling requirements in system analysis.

The purpose of this paper is to discuss the state of the art of finite element analysis of electrical machines and transformers. Electrical machines and transformers are prime examples of multi‐physical systems involving electromagnetics, thermal issues, fluid dynamics, structural mechanics as well as acoustic phenomena. An accurate operational performance with different electrical and mechanical load situations is more and more evaluated using various numerical analysis methods including the couplings between the various physical domains. Therefore, numerical analysis methods are increasingly utilized not only for the verification of contractual values of existing machines, but also for the initial design process and for the design optimization of new machines.

The finite element method is the most powerful numerical analysis method for such multi‐physical devices. Since optimizations with respect to the overall performance and also the total manufacturing costs will become more important, the utilization of coupled multi‐physical analyses is of growing interest. For the fast and powerful application of this numerical analysis method, special attention should be given to the requirements of these electromagnetic devices.

Various methods of coupling the different physical domains of multi‐field finite element analyses are described. Thereby, weakly coupled cascade algorithms can be used with most problems in the field of electrical machines and transformers. On the other hand, a prime objective is to derive comprehensive, multi‐physical simulation models which are easily incorporated into design tools used by engineering professionals.

The development of robust and reliable computer‐aided tools for an optimal design of multi‐physical devices such electrical machines and transformers has to argue about the best possible coupling of various simulation methods. Special consideration shall be paid more and more to a treatment of uncertainties and tolerances by means of statistical and probabilistic approaches.

The paper discusses state of the art of finite element analyses of the mentioned devices. Various optimized methods of modelling and analysis concerning the repetitive structure of electrical machines for electromagnetic analyses are compared with their advantages and drawbacks. Further, various methods of coupling the different domains of multi‐field analyses in case of electrical machines and transformers are described.

The purpose of this paper is to present a methodology based on an optimizer linked with electric finite element method (FEM) for automating the optimized design of power transformer insulation system structures.

The proposed methodology combines two stages to obtain the optimized design of transformer insulation system structures. First, an analytical calculation is carried out with the optimizer to search a candidate solution. Then, the candidate solution is numerically checked in detail to validate its consistency. Otherwise, these two steps are iteratively repeated until the optimizer finds a candidate solution according to the objective function.

The solutions found applying the proposed methodology reduce the inter-electrode distances compared to those insulation designs referenced in the literature for the same value of safety margin.

The proposed methodology explores a wide range of insulation system structures in an automated way which is not possible to do with the classical trial-and-error approach based on personal expertise.

The term “partial discharges” (PD) is a common term for various phenomena: discharges at points or edges of cylindrical conductors, in gases and gas insulated devices, liquid insulation materials, at borders between different insulation materials and, of course, in solid dielectrics. These phenomena result in insulation breakdowns, various disturbances to the environment, and after longer periods, some large‐scale failures. This paper presents the results of theoretical research of the behavior of a system of medium voltage covered conductors. This research work has been elaborated by the use of computer aided electric field calculations. For the confirmation of theoretical findings, practical measurements of partial discharges have been made.

The purpose of this paper is to research the induced flashover laws of different insulation materials under electrostatic electromagnetic pulse, and the induced flashover characteristics of different electrode structures are further explored.

According to standard IEC 61000–4-2, an experimental system of electrostatic electromagnetic pulse flashover for insulation materials is established. The induction flashover laws of polytetrafluoroethylene, epoxy resin and polymethyl methacrylate surface-mounted finger electrodes under the different intensity of electrostatic electromagnetic pulse are researched. The influence of the finger electrode, needle–needle electrode and needle–plate electrode on insulation flashover was compared. Secondary electron emission avalanche (SEEA) and field superposition theory are used to analyze the experimental results of electrostatic electromagnetic pulse induced flashover.

The larger the dielectric strength of insulation materials, the more difficult flashover occurs on the surface. The field superposition enhances collision ionization between electrons and gas molecules, which leads to the insulation materials surface induced flashover easily by electrostatic electromagnetic pulse. The sharper the electrode shapes on the insulation materials surface, the stronger the electric field intensity at the cathode triple junction, more initial electrons are excited to form the discharge channel, which easily leads to flashover on the surface of the insulating material.

The proposed field superposition combined with the SEEA method provides a new study perspective and enables a more rational, comprehensive analysis of electrostatic electromagnetic pulse induced flashover of insulation materials. The work of this paper can provide a reference for the safety protection of spacecraft in orbit under a strong electromagnetic field environment, increase the service life of spacecraft and improve the reliability of spacecraft’s safe operation in orbit. It provides a basis for the selection of insulation materials for equipment under the different intensities of the external electromagnetic environment.

This paper aims to explore the potential of ultrasonic additive manufacturing (UAM) to incorporate the direct printing of electrical materials and arrangements (conductors and insulators) at the interlaminar interface of parts during manufacture to allow the integration of functional and optimal electrical circuitries inside dense metallic objects without detrimental effect on the overall mechanical integrity. This holds promise to release transformative device functionality and applications of smart metallic devices and products.

To ensure the proper electrical insulation between the printed conductors and metal matrices, an insulation layer with sufficient thickness is required to accommodate the rough interlaminar surface which is inherent to the UAM process. This in turn increases the total thickness of printed circuitries and thereby adversely affects the integrity of the UAM part. A specific solution is proposed to optimise the rough interlaminar surface through deforming the UAM substrates via sonotrode rolling or UAM processing.

The surface roughness (Sa) could be reduced from 4.5 to 4.1 µm by sonotrode rolling and from 4.5 to 0.8 µm by ultrasonic deformation. Peel testing demonstrated that sonotrode-rolled substrates could maintain their mechanical strength, while the performance of UAM-deformed substrates degraded under same welding conditions ( approximately 12 per cent reduction compared with undeformed substrates). This was attributed to the work hardening of deformation process which was identified via dual-beam focussed ion beam–scanning electron microscope investigation.

The sonotrode rolling was identified as a viable methodology in allowing printed electrical circuitries in UAM. It enabled a decrease in the thickness of printed electrical circuitries by ca. 25 per cent.

Induction motors (IMs) are considered one of the most important elements of the industrial process. However, in this environment, these machines are subject to electrical and mechanical faults, which may cause significant financial losses. Thus, the purpose of this paper is to propose an optimal identification of inter-turn insulation faults present in the random wound IM.

The design approach deals with a simple technique, using the effect of the inter-turn fault in modifying the high-frequency components of the applied pulse-width-modulated voltage.

The change in insulation strength between the turns affects the capacitive component of the stator line current. Resulting changes in wave shapes of the applied voltage have been studied with respect to both the distance of inter-turn faults from line end and reduction in the insulation strength, and hence in the insulation resistance value.

Studies have been conducted by using computer simulation and validated by experiments. There is ample evidence that an impending and progressing inter-turn fault can be identified in adjustable speed drives driven by frequency converters by studying line-end coil-voltage waveforms.

This paper aims to focus on the finite element method in the frequency domain (FD-FEM) for the transient electric field in the non-sinusoidal steady state under the non-sinusoidal periodic voltage excitation.

Firstly, the boundary value problem of the transient electric field in the frequency domain is described, and the finite element equation of the FD-FEM is derived by Galerkin’s method. Secondly, the constrained electric field equation on the boundary in the frequency domain (FD-CEFEB) is also derived, which can solve the electric field intensity on the boundary and the dielectric interface with high accuracy. Thirdly, the calculation procedures of the FD-FEM with FD-CEFEB are introduced in detail. Finally, a numerical example of the press-packed insulated gate bipolar transistor under the working condition of the repetitive turn-on and turn-off is given.

The FD-CEFEB improves numerical accuracy of electric field intensity on the boundary and interfacial charge density, which can be achieved by modifying the existing FD-FEMs’ code in appropriate steps. Moreover, the proposed FD-FEM and the FD-CEFEB will only increase calculation costs by a little compared with the traditional FD-FEMs.

The FD-CEFEB can directly solve the electric field intensity on the boundary and the dielectric interface with high accuracy. This paper provides a new FD-FEM for the transient electric field in the non-sinusoidal steady state with high accuracy, which is suitable for combined insulation structure with a long time constant.