Minimization Of AC Losses Research Articles

Material Tradeoff of Rotor Architecture for Lightweight Low-Loss Cost-Effective Sustainable Electric Drivetrains

The art of the successful design of high-speed electrical machines comes with many challenges in the mass, size, reliability, and energy efficiency. Material engineering of electrical machines has been identified as a key solution for higher power dense electric drivetrains. One of the main challenges at high speed is the eddy-current losses in the active electromagnetic parts, especially magnetic materials and permanent magnets (PMs). This study is devoted to the selection of PM rotor materials using multidisciplinary design optimization for a high-speed electric drivetrain. Beside AC loss minimization, more disciplines are considered, such as the minimization of weight, and cost. Different laminations are investigated with different magnetic properties as well as cost. Additionally, different PMs are optimized considering low-cost ferrite and high-coercivity permanent magnets (HCPMs). Moreover, the optimal materials are identified which have the best balance between loss, weight, cost, ripples. Finally, different rotor designs are prototyped, assembled, and tested using the same stator configuration. Also, the best rotor design is selected, and the electromagnetic performance is measured and compared with conventional designs. The optimal design results in 8% extra torque with at least 20% weight reduction.

Flux-transfer losses in helically wound superconducting power cables

Minimization of ac losses is essential for economic operation of high-temperature superconductor (HTS) ac power cables. A favorable configuration for the phase conductor of such cables has two counter-wound layers of HTS tape-shaped wires lying next to each other and helically wound around a flexible cylindrical former. However, if magnetic materials such as magnetic substrates of the tapes lie between the two layers, or if the winding pitch angles are not opposite and essentially equal in magnitude to each other, current distributes unequally between the two layers. Then, if at some point in the ac cycle the current of either of the two layers exceeds its critical current, a large ac loss arises from the transfer of flux between the two layers. A detailed review of the formalism, and its application to the case of paramagnetic substrates including the calculation of this flux-transfer loss, is presented.

Design Optimization, Series Production, and Testing of the SIS100 Superconducting Magnets for FAIR

SIS100, the core machine of the FAIR project, is being realized now, with the dipole series already ordered. This machine uses fast ramped superconducting dipole magnets (4 T/s, 1 Hz operation cycle), which were optimized to reduce the ac loss and to provide adequate end fields. We present the actual status of the design optimization for the superconducting main magnets as well as of the corrector magnet units. Their series production is now launched and the testing strategy is clarified. The key issues of ac loss minimization, hydraulic resistance, and test facility built is discussed.

The development of a Roebel cable based 1 MVA HTS transformer

This paper describes recent experimental results in a continuing program to develop a 1 MVAdemonstration transformer that employs HTS Roebel cable for the high current windings. Theelectrical design parameters of the transformer are presented, including the configuration ofthe specially developed Roebel cable. This paper discusses estimation of the cableIc frommeasured Ic(B) data for samples of the strands, AC loss minimization using flux diverters, proving thesuitability of the polyimide insulation scheme to withstand the effects of a high voltageimpulse and modelling and experimental verification of the fault current limiting behaviourexpected from the HTS conductor.

Numerical Study on AC Loss Reduction of Multi-Pole HTS Coil by Optimal Design of Winding Cross Section of Element Coil

We study the optimal design of 2- and 4-pole coils wound by YBCO tapes as the case studies of the optimal design of the multiple-coil system based on the AC loss minimization. The winding cross sections of the element coils of the 2- and 4-pole coils were optimized starting from the conventional rectangular cross section to minimize the AC loss. The result shows that the AC loss in the optimized coil is significantly reduced and the critical current of the optimized coil is increased compared with the base coil. According to the results, the validity of our optimal design method is verified to effectively reduce the AC loss in the multi-pole coils wound by the YBCO tapes. Some disadvantageous points of the optimized coil are also discussed.

Numerical minimization of AC losses in coaxial coated conductor cables

Power cables are one of the most promising applications for the superconducting coated conductors. In the AC use, only small resistive loss is generated, but the removal of the dissipated heat from the cryostat is inefficient due to the large temperature difference. The aim of this work is to minimize the AC losses in a multilayer coaxial cable, in which the tapes form current carrying cylinders. The optimized parameters are the tape numbers and lay angles in these cylinders. This work shows how to cope with the mechanical constraints for the lay angles and discrete tape number in optimization. Three common types of coaxial cables are studied here to demonstrate the feasibility of optimization, in which the AC losses were computed with a circuit analysis model formulated here for arbitrary phase currents, number of phases, and layers. Because the current sharing is practically determined by the inductances of the layers, the optima were obtained much faster by neglecting the nonlinear resistances caused by the AC losses. In addition, the example calculations show that the optimal cable structure do not usually depend on the AC loss model for the individual tapes. On the other hand, depending on the cable type, the losses of the optimized cables may be sensitive to the lay angles, and therefore, we recommend to study the sensitivity for the new cable designs individually.

Study on Optimal Design of High Temperature Superconducting Coil Based on AC Loss Minimization

This paper presents an optimal design method of winding cross section of high temperature superconducting coils wound by Bi2223/Ag tape based on AC loss minimization. We try to optimize the winding cross section starting from the conventional HTS coil with the rectangular cross section to minimize the AC loss. An example of the optimal cross section coil is presented. The result shows that the AC loss in the optimized coil is significantly reduced and the critical current of the optimized coil is increased compared with the rectangle cross section coil. It is verified that our optimal design method is effective to reduce the AC loss in the HTS coil. The disadvantageous points of the optimized coil are also discussed.

Experimental Set Up to Measure AC Losses of HTS in Rotating Magnetic Field

The apparatus described here is designed to measure the total ac loss in 2G tape subjected to a rotating magnetic field of up to 1 Tesla applied perpendicular to the tape axis and at speeds of up to 3600 rpm, while carrying a transport current. Both thermal and electrical measurement techniques are incorporated in the apparatus. The data collected from the apparatus will be used to assist the design of superconducting machines in which the superconductor is used for the stator as well as the rotor and where the minimization of AC losses is crucial to the success of the machine. The measurement of ac losses will give results that are difficult to predict from mathematical modeling.

Numerical Study on AC Loss Minimization of Multi-Layer Tri-Axial HTS Cable for 3-Phase AC Power Transmission

This paper presents numerical studies on structures to minimize AC losses in high temperature superconducting tri-axial multi-layer three-phase cable conductors. The simulations were performed for tri-axial cables of 2-layer/phase configuration under 3-phase AC operation. From the numerical results, the relation between the AC loss and the layer-to-layer current sharing showed that the AC loss can be minimized by adjusting the layer-to-layer current sharing. The reason was clarified from the numerical data of the current density profiles across the superconducting layers. Based on the numerical analysis, the twist pitch formulation for the AC loss minimization was obtained.

Ac Loss analysis for superconducting generator armatures wound with subdivided Y–Ba–Cu–O coated tape

Advances in Y–Ba–Cu–O coated thin film tape may allow narrow filaments with very high current density on a thin metal alloy substrate which is separated from the superconductor by a dielectric buffer. These tapes will exhibit minimized ac loss by subdividing the Y–Ba–Cu–O layer with barriers which exhibit high electrical resistance. Assuming a fully penetrated magnetic field, low loss conductor concepts were incorporated into 1 MW armature designs for various configurations of Y–Ba–Cu–O conductors over the frequency range 50–1000 Hz. Low ac loss armature conductor designs are developed for megawatt class generators loss for both a 50–60 Hz utility application and a higher frequency aircraft application. Conductor design tradeoffs are discussed and ac loss minimization techniques compatible with realistic Y–Ba–Cu–O coated conductor processing are considered. The ac loss in Y–Ba–Cu–O armature windings of a synchronous alternator may for the first time permit practical, lightweight all-cryogenic generators which can deliver ⩾ megawatt at frequencies much greater than 50–60 Hz.

Superconductor coil geometry and ac losses

An empirical relation is presented which allows simple computation of volume-averaged winding fields from central fields for coils of small rectangular cross sections. This relation suggests that, in certain applications, ac-loss minimization can be accomplished by use of low winding densities, provided that hysteresis losses are independent of winding density. ac-loss measurements on coils wound of twisted multifilamentary composite superconductors show no significant dependence of ac losses on winding density, thus permitting the use of winding density as an independent design parameter in loss minimization.