AC losses in HTS tapes in applied longitudinal magnetic fields at variable temperatures

In most power devices, the conductor is carrying an ac transport current while it is exposed to an ac magnetic field transverse to the current path. In certain applications, such as power cables or a control winding in a controllable reactor, the conductors are exposed to a magnetic field component longitudinal to the tape axis that is parallel to the current path. To create an improved base for the design of such power devices it is of interest to study the losses in high-temperature superconductor tapes due to longitudinal field in detail. We have investigated the losses at several temperatures of a nontwisted multifilamentary Bi-2223 tape when it was exposed to a longitudinal magnetic field. The losses were measured with a calorimetric method and the results were compared with the critical state hysteresis loss model. The hysteresis losses are dominating at power frequencies (50, 60 Hz) in the investigated field range 2-200 mT and are accurately described by the critical state hysteresis model.     

Model of the flux flow losses in a high-temperature superconducting tape exposed to both AC and DC transport currents and magnetic fields

Recent progress in the high-temperature superconductor technology will probably be of importance for future power applications. In these applications, the power loss is a very important quantity, which has to be described in a relevant manner to obtain an optimum utilization of the conductor. In most power applications the magnitude of the transport current will be quite close to the critical current. In addition to the hysteresis losses, for such high currents, the flux flow losses have to be taken into account. We present a semiempirical model of the flux flow losses in a tape shaped conductor, based on measurements and reasonable physical assumptions. The model gives the flux flow loss as function of temperature, a transport current consisting of both ac and dc components and an applied homogeneous magnetic field with an amplitude proportional to the current.     

DC-probes for electric field distribution measurements

The principles of how DC fields can be measured using an isolated probe coupled by fiber optics to a separate receiver are discussed. The construction of some practical systems is described, with attention given to induced current, voltage, power, and dipole systems. The electric fields around a full size wall bushing energized to 600 kV in rain were measured. The results of this measurement and other measurements are presented, demonstrating the usefulness of isolated DC field measurements     

Losses in a BSCCO/Ag tape carrying AC transport currents in ACmagnetic fields applied in different orientations

In most prospective electric power applications of high-temperature superconductors (HTSs), the conductor is wound in a coil configuration. For a coil of finite length, the magnetic field orientation is axial in the middle of the coil, while the field contains a substantial radial component at the coil ends. In a superconducting BSCCO/Ag tape, the AC losses depend strongly on the orientation of the magnetic field. In this study, we present experimental results of the AC losses in a multifilamentary silver-sheathed Bi-2223 HTSs tape, carrying alternating transport currents in externally applied alternating magnetic fields at different orientations, with respect to the face of the tape and perpendicular to the transport current. The AC losses were measured calorimetrically, at fixed temperature and frequency. The results are compared to semi-empirical models of the AC losses in HTSs tape. We present a more general model of the angular dependence of the AC losses     

Poisonings in animals: the 1993-1994 report of the American Association of Poison Control Centers

This study was undertaken to compare the detection rate of hepatic space occupying lesion (SOL)s between computed tomography during arterial portography (CT-AP) and magnetic resonance imaging during arterial portography (MR-AP) and the differences in time intensity curve on MR-AP between HCC, metastatic tumor, FNH, and hemangioma. We performed CT-AP and MR-AP in 17 patients including 14 cases of HCC and one each of metastasis, FNH, and hemangioma. MR-AP was performed by Turbo-FLASH sequence. There was no statistically significant difference between CT-AP and MR-AP in detecting satellite lesions in terms of smallest diameter and number of flow defects (p > 0.05). Hemangioma showed rapid enhancement after the first pass and, consequently, the same enhancement as the hepatic parenchyma. MR-AP was comparable to CT-AP in the detection of hepatic SOLs. Hemangioma showed an enhancement pattern different from those of HCC, metastatic tumor, and FNH, which showed patterns similar to each other.     

Melaleuca oil poisoning

A 23-month-old boy became confused and was unable to walk thirty minutes after ingesting less than 10 mL of T36-C7, a commercial product containing 100% melaleuca oil. The child was referred to a nearby hospital. His condition improved and he was asymptomatic within 5 hours of ingestion. He was discharged to home the following day. Melaleuca oil, extracted from the Melaleuca alternifolia, contains 50-60% terpenes and related alcohols. Clinical experience with products containing melaleuca oil is limited. This case report suggests that ingestion of a modest amount of a concentrated form of this oil may produce signs of toxicity.     

Magnetic circuit for a controllable reactor

Reactive power compensation is vital for obtaining efficient operation of long transmission power lines or cables. A controllable shunt reactor that controls the transmission of power by continuous reactive power compensation will reduce the transmission losses and increase the transmission capacity of active power. We show that the saturation phenomena of iron and the high current density of a high-temperature superconductor can be utilized to design controllable reactors with large dynamic range, low losses, and limited harmonic distortion. We have designed and constructed a small-scale prototype of a controllable shunt reactor with a high-temperature superconductor control winding. We present a simple model of the magnetic circuit of the controllable reactor and we compare calculations from the model to experimental measurements on the controllable reactor.     

Impact of DC components in transport current and external magnetic field on hysteresis losses in an HTS tape

The high-temperature superconductor (HTS) development is presently intensive, and one can expect that HTSs will be used in different electric devices in the future. In some of these devices, e.g., a magnetostrictive actuator, the conductor will be exposed to both ac and dc transport currents and external magnetic fields. One of the most important parameters in the design of electric devices is the power loss. It is, therefore, of importance to develop models that are able to predict the power loss in devices based on HTSs. In this paper, we present an experimental characterization of the hysteresis losses in an HTS tape exposed to ac or dc transport currents in combination with external magnetic fields. The experimental results are compared to some existing models based on the critical state model. The power loss was measured on a multifilamentary Bi-2223 tape at constant temperature (70 K) and frequency (50 Hz).