Electromagnetic losses in magnetic shields for buried high voltage cables

The electromagnetic losses and shielding efficiency of shields for a buried three phase high voltage cable are studied for several shielding configurations. The shields are U-shaped gutters covered with plates, and the power cables are positioned either in trefoil or in flat configuration. The shielding efficiency and the losses are compared for shields with the same geometry but several shielding materials: aluminium, and two ferromagnetic steel grades. The numerical models are validated with experimental results. From the experiments, it is observed that the average reducing factor of the flux density is about 7 with the flat cable configuration while the average reducing factor of the flux density is about 5 with the trefoil cable configuration. But the power losses in the DX52 shield for trefoil configuration is about 40% lower compared to the flat configuration. In case of trefoil configuration, the losses are 12.14 W/m per meter length in the shield for a current of 750 A. Next to the shield material and the cable configuration, the paper investigates the influence of several parameters on both the shielding efficiency and the losses: the size of the shield, the current amplitude in the cable and the thickness of the shield

Optimal design and implementation of a drivetrain for an ultra-light electric vehicle

This paper presents an integrated design of a drivetrain for a single-person ultra-light electric vehicle (ULEV). To calculate losses and efficiency of the inverter, the permanent magnet synchronous machines (PMSMs) and the gearbox, parameterised analytical models are used. For the gearbox - which has a single gear ratio - the studied parameters are the gear ratio, the number of stages, the number of teeth and the module of each spur gear combination. The novelty of the paper is that it learns how the total average efficiency and the total mass of the drivetrain depend on the gear ratio, on the number of stages in the gearbox, on the motor parameters and on the chosen several driving cycles including the new European driving cycle (NEDC). On the basis of the presented results, it is possible to choose the right configuration of power electronics, PMSM and gearbox in order to have a good trade-off between high efficiency and low mass

A Case Study on Fault Detection in Power Transformers Using Dissolved Gas Analysis and Electrical Test Methods

This paper presents methodologies for power transformer fault diagnosis using dissolved gas analysis and electrical test methods. These methods are widely used in determination of inception faults of power transformers. Dissolved gas analysis test provides fault diagnosis of power transformers. On the other hand the electrical test methods are used for detection of root causes and fault locations and they provide more specific information about the faults. The aim of this work is to study the faults that are measured and recorded in Turkish Electricity Transmission Company (TEIAS) power systems. For this purpose, four specific cases are considered and analyzed with dissolved gas analysis and electrical testing methods. Three of these cases are defective situations and one case is a non-defective situation. These real cases of measurements have been analyzed with both methods in detail. Assessment results showed that a single method cannot yield accurate enough results in some specific fault conditions. Therefore it was concluded that cooperation of both methods in the assessment of fault condition gives more trustworthy results

Energy Management System Optimization for Battery-Ultracapacitor Powered Electric Vehicle

Energy usage and environment pollution in the transportation are major problems of today’s world. Although electric vehicles are promising solutions to these problems, their energy management methods are complicated and need to be improved for the extensive usage. In this work, the heuristic optimization methods; Differential Evolution Algorithm, Genetic Algorithm and Particle Swarm Optimization, are used to provide an optimal energy management system for a battery/ultracapacitor powered electric vehicle without prior knowledge of the drive cycle. The proposed scheme has been simulated in Matlab and applied on the ECE driving cycle. The differences between optimization methods are compared with reproducible and measurable error criteria. Results and the comparisons show the effectiveness and the practicality of the applied methods for the energy management problem of the multi-source electric vehicles

Influence of the temperature on energy management in battery-ultracapacitor electric vehicles

Energy management strategies for an electric vehicle (EV) with multiple power sources have been widely described in literature. The investigated energy sources are batteries, ultracapacitors, fuel cells, flywheels and solar panels. The management strategy decides how to combine two or more sources in an optimal way. However, the behavior of these sources and also the behavior of the electric drives depend on their temperature. Moreover, the temperature can have extreme values in automotive applications and affect the energy management task. In this paper, to investigate the temperature effect on battery/ultracapacitor powered EV, temperature dependent models are presented for these storage components, as well as for the drive train components itself: power electronics and motor. The average motor iron loss and ultracapacitor loss tend to decrease with increasing temperature, while the average motor copper loss and power electronics loss tend to increase with increasing temperature. These two opposing trends cause the total loss of the drive train to have a rather small variation with temperature for the considered EV and in the considered temperature range. By consequence, the energy management strategy of the EV does not have to depend on the temperature in order to obtain maximal efficiency

The Comparison of Thyroxine versus Thyroxine plus Oral Iodine in the Treatment of Congenital Hypothyroidism due to Iodine Deficiency

Aim: Iodine deficiency is one of the most important causes of congenital hypothyroidism. In addition to thyroid hormone replacement, iodine supplementation is also given to newborns with congenital hypothyroidism due to iodine deficiency. We aimed to determine whether it is beneficial to administer iodine supplementation in addition to the L-thyroxine (L-T-4) treatment of newborns with congenital hypothyroidism due to iodine deficiency. Materials and Methods: Of 51 newborns, 26 who were diagnosed with congenital hypothyroidism due to iodine deficiency were treated with L-T-4. The remaining 25 cases were given L-T-4 plus 100 g/day of oral iodine. Free triiodothyronine (fT(3)), free thyroxine (fT(4)), thyroid-stimulating hormone (TSH), thyroglobulin (TG), thyroid volume, urine iodine and breast milk iodine levels were measured in the first and third months of treatment, and the data were compared between the two groups. Results: First-and third-month values of fT(3), fT(4), TSH, TG and thyroid volume for both groups were statistically similar. There was no significant difference between the two groups in respect to falling levels of fT(3) and TSH, the rate of increase of fT(4) levels or the shrinkage rate of thyroid volume. Conclusion: In this study, the addition of oral iodine to L-T-4 treatment provided no benefit compared to treatment with L-T-4 alone. (C) 2014 S. Karger AG, Basel &nbsp; Abstract AIM: Iodine deficiency is one of the most important causes of congenital hypothyroidism. In addition to thyroid hormone replacement, iodine supplementation is also given to newborns with congenital hypothyroidism due to iodine deficiency. We aimed to determine whether it is beneficial to administer iodine supplementation in addition to the L-thyroxine (L-T4) treatment of newborns with congenital hypothyroidism due to iodine deficiency. MATERIALS AND METHODS: Of 51 newborns, 26 who were diagnosed with congenital hypothyroidism due to iodine deficiency were treated with L-T4. The remaining 25 cases were given L-T4 plus 100 &mu;g/day of oral iodine. Free triiodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone (TSH), thyroglobulin (TG), thyroid volume, urine iodine and breast milk iodine levels were measured in the first and third months of treatment, and the data were compared between the two groups. RESULTS: First- and third-month values of fT3, fT4, TSH, TG and thyroid volume for both groups were statistically similar. There was no significant difference between the two groups in respect to falling levels of fT3 and TSH, the rate of increase of fT4 levels or the shrinkage rate of thyroid volume. CONCLUSION: In this study, the addition of oral iodine to L-T4 treatment provided no benefit compared to treatment with L-T4 alone. &nbsp;</p

Integrated model of power electronics, electric motor, and gearbox for a light EV

This study presents a model of a drivetrain for an integrated design of a light electric vehicle (EV). For the drivetrain of each front wheel of the single-person, battery-powered EV tricycle consists of a battery, an inverter, and an outer rotor permanent magnet synchronous motor (PMSM), which is connected to an in-wheel gearbox. The efficiency of the inverter, motor, and gearbox is analyzed over the New European Driving Cycle. To calculate the losses and efficiency of the PMSM, the power electronics in the inverter and gearbox are used. The analytical models provide a fat, but less accurate result, useful for optimization purposes. To accurately predict the efficiency of the PMSM, a finite element model is used. The models are validated by test setups. Correspondingly, a good agreement between the measurements and the calculated results is achieved. A parameter study is performed to investigate the influence of the detailed component parameters (i.e., outer rotor radius, gear ratio, and number of pole pairs and stator slots) on the average efficiency of the drivetrain

Influence of contact resistance on shielding efficiency of shielding gutters for high-voltage cables

The shielding of buried three-phase high-voltage power lines can be done by placing them in conducting ferromagnetic U-shaped gutters covered with plates. In case of a perfect electrical contact between adjacent gutters and between adjacent cover plates, induced currents in the shield efficiently reduce the magnetic field generated by the cables. As however a perfect contact cannot be guaranteed, in practice, it is useful to quantify the effect of a defective electrical contact on the field reduction. From two-dimensional/ three-dimensional finite element computations and experiments, the influence of the contact resistance on the shielding efficiency is investigated, as a function of the ratio of axial length to height of the shield elements. Furthermore, the effect of other parameters on the shielding efficiency is studied: the ratio of axial length to height, a parasitic air gap between the gutter and the cover plate and the type of the shield material. It was found that a low contact resistance deteriorates much more the shielding in case of an aluminium shield than in case of a steel shield. As expected, the effect is larger for shield elements with relatively short axial length with regard to the other dimensions. Nevertheless, the effect remains quite significant for aluminium shields with practically convenient dimensions