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Sixteen different commercial bolted connectors for 50 and 240 [mm.sup.2] stranded aluminum cable conductors have been examined in order to identify and clarify the correlations between the quality of a connector and its design characteristics, material usage, assembly procedures, bolt numbers and configurations and other relevant parameters. The quality is assessed with basis in resistance measurements after short circuit testing and during thermal cycling as specified by the IEC 61238-1 standard. The tightening torque of the bolts was measured during connector assembly, and the resulting axial compressive forces were calculated. A very strong correlation is observed between this compressive force and the connector quality; large forces give connections with low and stables resistances. The various other design parameters considered are found to have significantly less or in some cases hardly any notable influence on the electrical test results. Index Terms--Aluminum power conductors, connectors, contact mechanical factors, contact resistance, power cable connecting, testing.

How to calculate the efficiency analysis of a high-temperature superconducting induction heater is discussed.

Design, construction and testing of a small-scale high-temperature superconducting (HTS) induction heater is described and discussed.

The ac losses of a Bi-2223 high-temperature superconductive (HTS) tape are investigated with reference to field orientation. Applications of results can involve calculating losses in the windings of devices such as transformers or reactor HTS coils.

Geomagnetically induced currents (GICs) and the converter modulation effect are the two main causes for dc magnetisation in power transformers. It is well known that a small dc‐bias can saturate a large transformer and thereby generate high unbalanced magnetising currents, imposing a serious risk of excessive power losses and local overheating. Magnetising currents due to GIC phenomena have been studied extensively, whereas studies on converter related dc‐bias are few. In particular, a discussion on loss characteristics related to converter modulation lacks. In this study, the dc‐bias of common mode and differential mode in a three‐phase, three‐limb transformer is investigated experimentally. Additionally, to interpret the physical phenomena, the system was modelled using the finite element method. The results revealed that the power losses are significantly influenced by the dc current direction, arrangement of the structural parts, and the method of winding connection. [ABSTRACT FROM AUTHOR]

Leakage flux penetrating laminated iron cores in power transformers and large generators induces eddy current and local loss. Due to the strong magnetic anisotropy of the lamination structure, the penetrating flux tends to saturate the lamination in its plane, even when the incident stray flux density is low. Therefore, the combined effect of anisotropy and nonlinearity has a great impact on the eddy current distribution and the associated power losses. Moreover, the incident normal flux often interacts with the main flux, where the phase angle between the two fluxes may play a significant role. A measurement device is developed to emulate the actual leakage flux in a steel lamination and the power losses are measured at the flux densities of various magnitudes and phases. The measurement results are compared and interpreted by the results obtained from a finite-element analysis, where the homogenization approach for material modeling is implemented, taking the combined effect of magnetic anisotropy and the saturation into account. [ABSTRACT FROM AUTHOR]

Computation of iron losses in transformers requires significant numerical efforts, particularly under magnetic saturation when the magnetic non‐linearity needs to be considered. This study proposes a Fourier method to calculate the magnetic flux density used for the iron loss evaluation in transformers under saturation. It includes pre‐processing of the non‐linear material. A permeability frequency spectrum is obtained from Fourier analysis, where the fundamental part is used as a magnetisation definition and the harmonic components are used for core loss calculation. The proposed method offers a time‐efficient tool to calculate core loss under various saturation levels and non‐sinusoidal excitation currents. The influence of the definition of the core material on the leakage field and the stray loss calculation is studied and compared with existing methods. The proposed methods have been implemented and validated in two‐ and three‐dimensional finite‐element models with isotropic and anisotropic cores. The results yield accuracy comparable to that of a time‐domain calculation. Furthermore, the influences of various effective permeability methods on the leakage field and the associated stray loss are compared and discussed. [ABSTRACT FROM AUTHOR]

A direct-drive superconducting generator (DDSCG) is proposed for 10 MW wind turbines in the INNWIND.EU project. To fit the generator into the "king-pin" conceptual nacelle design, the generator structure with inner stationary super-conducting (SC) field winding and outer rotating copper armature winding is investigated in the first research phase. Since the cost is an important performance indicator for this application, this paper presents a method to minimize the active material cost of the "king-pin" fitted DDSCG. In this method a relatively fast optimization program is developed with 2D non-linear finite element models. By implementing this method, three typical superconducting generator topologies are compared in terms of the active material cost and mass, the synchronous reactance and the phase resistance. The optimization method and the comparison results provide the DDSCG designers with a guideline for selecting a suitable machine topology. [ABSTRACT FROM AUTHOR]

For transmission of large amounts of electric energy across long sea crossings, the so-called mass-impregnated HVDC subsea cable has for a long time been, and still remains, the state-ofthe- art technology [1]. The electrical insulation of such cables consists of Kraft paper (or polypropylene laminated paper as in a recent development) impregnated with high-viscosity oil (the "mass"). They are also referred to as mass-impregnated nondraining (MIND) cables. The insulation is enclosed by a lead sheath that prevents water ingress. External layers of polyethylene, steel tapes, steel wire armour, polypropylene yarn, and an asphaltic compound provide mechanical strength and protection against corrosion. [ABSTRACT FROM PUBLISHER]

The induction heater for aluminum, copper and brass extrusion billets is an application where high-temperature superconductors (HTSs) provide clear benefits compared to conventional technology. With an energy efficiency of just some 50% for conventional technology and limitations in processing speed, the potential for improvements is evident. A novel heater design based on superconductors, and a fast product development have led to an industrial breakthrough. With one unit in operation since August 2008 and four more sold, the superconducting induction heater has become the first true commercial HTS product. Radical efficiency increases, improvements in process speed, quality and cost have been demonstrated in a rough industrial environment. In this paper we explain how to fully utilize the superconductor in this application by altering the established concepts of induction heating. The electromagnetic realization as well as cryogenic integration based on off-the-shelf cryo-coolers are described. Furthermore, operational experience from heating up 10,000 tons of aluminum (350,000 billets) in the first commercial installation is presented. [ABSTRACT FROM AUTHOR]