This page has only limited features, please log in for full access.

Unclaimed
Francesco Grilli
Institute for Technical Physics, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany, 76344

Basic Info

Basic Info is private.

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

The user biography is not available.
Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Review
Published: 16 April 2021 in Energies
Reads 0
Downloads 0

Superconductor technology has recently attracted increasing attention in power-generation- and electrical-propulsion-related domains, as it provides a solution to the limited power density seen by the core component, electrical machines. Superconducting machines, characterized by both high power density and high efficiency, can effectively reduce the size and mass compared to conventional machine designs. This opens the way to large-scale purely electrical applications, e.g., all-electrical aircrafts. The alternating current (AC) loss of superconductors caused by time-varying transport currents or magnetic fields (or both) has impaired the efficiency and reliability of superconducting machines, bringing severe challenges to the cryogenic systems, too. Although much research has been conducted in terms of the qualitative and quantitative analysis of AC loss and its reduction methods, AC loss remains a crucial problem for the design of highly efficient superconducting machines, especially for those operating at high speeds for future aviation. Given that a critical review on the research advancement regarding the AC loss of superconductors has not been reported during the last dozen years, especially combined with electrical machines, this paper aims to clarify its research status and provide a useful reference for researchers working on superconducting machines. The adopted superconducting materials, analytical formulae, modelling methods, measurement approaches, as well as reduction techniques for AC loss of low-temperature superconductors (LTSs) and high-temperature superconductors (HTSs) in both low- and high-frequency fields have been systematically analyzed and summarized. Based on the authors’ previous research on the AC loss characteristics of HTS coated conductors (CCs), stacks, and coils at high frequencies, the challenges for the existing AC loss quantification methods have been elucidated, and multiple suggestions with respect to the AC loss reduction in superconducting machines have been put forward. This article systematically reviews the qualitative and quantitative analysis methods of AC loss as well as its reduction techniques in superconductors applied to electrical machines for the first time. It is believed to help deepen the understanding of AC loss and deliver a helpful guideline for the future development of superconducting machines and applied superconductivity.

ACS Style

Hongye Zhang; Zezhao Wen; Francesco Grilli; Konstantinos Gyftakis; Markus Mueller. Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines. Energies 2021, 14, 2234 .

AMA Style

Hongye Zhang, Zezhao Wen, Francesco Grilli, Konstantinos Gyftakis, Markus Mueller. Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines. Energies. 2021; 14 (8):2234.

Chicago/Turabian Style

Hongye Zhang; Zezhao Wen; Francesco Grilli; Konstantinos Gyftakis; Markus Mueller. 2021. "Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines." Energies 14, no. 8: 2234.

Journal article
Published: 14 April 2021 in IEEE Transactions on Applied Superconductivity
Reads 0
Downloads 0

Although the H-formulation has proven to be one of the most versatile formulations used to accurately model superconductors in the finite element method, the use of vector dependent variables in non-conducting regions leads to unnecessarily long computation times. Additionally, in some applications of interest, the combination of multiple magnetic components interacting with superconducting bulks and/or tapes leads to large domains of simulation. In this work, we separate the magnetic field into a source and reaction field and use the H-phi formulation to efficiently simulate a superconductor surrounded by magnetic bodies. We model a superconducting cube between a pair of Helmholtz coils and a permanent magnet levitating above a superconducting pellet. In both cases, we find excellent agreement with the H-formulation, while the computation times are reduced by factors of nearly three and four in 2-D and 3-D, respectively. Finally, we show that the H-phi formulation is more accurate and efficient than the H-A formulation in 2-D.

ACS Style

Alexandre Arsenault; Frederic Sirois; Francesco Grilli. Efficient Modeling of High-Temperature Superconductors Surrounded by Magnetic Components Using a Reduced H–$\phi$ Formulation. IEEE Transactions on Applied Superconductivity 2021, 31, 1 -9.

AMA Style

Alexandre Arsenault, Frederic Sirois, Francesco Grilli. Efficient Modeling of High-Temperature Superconductors Surrounded by Magnetic Components Using a Reduced H–$\phi$ Formulation. IEEE Transactions on Applied Superconductivity. 2021; 31 (4):1-9.

Chicago/Turabian Style

Alexandre Arsenault; Frederic Sirois; Francesco Grilli. 2021. "Efficient Modeling of High-Temperature Superconductors Surrounded by Magnetic Components Using a Reduced H–$\phi$ Formulation." IEEE Transactions on Applied Superconductivity 31, no. 4: 1-9.

Journal article
Published: 26 March 2021 in IEEE Access
Reads 0
Downloads 0

With recent advances in second-generation high temperature superconductors (2G HTS) and cable technologies, various numerical models based on finite-element method (FEM) have been proposed to help interpret measured AC loss and assist cable design. The T-A formulation, implemented in COMSOL, shows great potential for reducing the overall computation costs. In this paper, the performance of the T-A formulation for calculating the AC loss of coated superconductors and cables were assessed and compared against the widely accepted H formulation, with benchmark model of a single REBCO tape in 2D/3D and a 14-strand Roebel cable. Evaluation and comparison on key metrics including the computation time, the number of degrees of freedom and the numerical accuracy were presented, which could provide a reference for researchers in applying the T-A formulation for AC loss calculation.

ACS Style

Yufan Yan; Timing Qu; Francesco Grilli. Numerical Modeling of AC Loss in HTS Coated Conductors and Roebel Cable Using T-A Formulation and Comparison With H Formulation. IEEE Access 2021, 9, 49649 -49659.

AMA Style

Yufan Yan, Timing Qu, Francesco Grilli. Numerical Modeling of AC Loss in HTS Coated Conductors and Roebel Cable Using T-A Formulation and Comparison With H Formulation. IEEE Access. 2021; 9 (99):49649-49659.

Chicago/Turabian Style

Yufan Yan; Timing Qu; Francesco Grilli. 2021. "Numerical Modeling of AC Loss in HTS Coated Conductors and Roebel Cable Using T-A Formulation and Comparison With H Formulation." IEEE Access 9, no. 99: 49649-49659.

Accepted manuscript
Published: 22 March 2021 in European Journal of Physics
Reads 0
Downloads 0

High-temperature superconductors (HTS) can be superconducting in liquid nitrogen (77 K) at atmospheric pressure, which holds immense promises for our future such as nuclear fusion, compact medical devices and efficient power applications. In a power system, high short-circuit currents can exceed the operational current by more than ten times, putting at risk many parts of the system. Superconducting fault current limiters (SFCL) can limit the prospective fault current without disconnecting the power system, and are thus becoming increasingly attractive for future grids. With a growing interest in modeling and commercializing SFCL, the question of how to teach and to explain their operation to students has arisen. In order to help students visualize the potential use and benefits of a SFCL, we created an executable and a web application using COMSOL Multiphysics. This executable (and the web application) allows students to investigate the electro-thermal response of a resistive SFCL. The executable solves a 1-~D electro-thermal model of the SFCL under AC fault conditions, evaluating important figures of merit such as the limited current, the prospective current and the maximum temperature reached within the tape. Finally, the geometrical parameters as well as the superconducting properties of the device can be modified. The importance of the amount of silver stabilizer necessary to protect the device from over-heating occurring during a fault current can be investigated. In addition, the effects of having a sharp nonlinear transition from the superconducting to the normal state (intrinsic property of the superconductor) to obtain a current limitation can be well explored. The executable allows the users to learn about the benefits of superconductors in real-life applications, without the prerequisite of extensive modeling or experimental setup. The executable can be downloaded from the HTS modeling website and run on the most commonly used operating systems.

ACS Style

Nicolò Riva; Francesco Grilli; Bertrand Dutoit. Superconductors for power applications: an executable and web application to learn about resistive fault current limiters. European Journal of Physics 2021, 42, 045802 .

AMA Style

Nicolò Riva, Francesco Grilli, Bertrand Dutoit. Superconductors for power applications: an executable and web application to learn about resistive fault current limiters. European Journal of Physics. 2021; 42 (4):045802.

Chicago/Turabian Style

Nicolò Riva; Francesco Grilli; Bertrand Dutoit. 2021. "Superconductors for power applications: an executable and web application to learn about resistive fault current limiters." European Journal of Physics 42, no. 4: 045802.

Accepted manuscript
Published: 17 March 2021 in Superconductor Science and Technology
Reads 0
Downloads 0

In order to reliably make use of superconductors in wind generators, a double-stator superconducting flux modulation generator is proposed here to avoid rotation of field coils and armature windings. The superconducting field coils are located in the inner stator while the armature windings are placed in the outer stator. In this way, the stationary-rotatory couplings of current and cryogenic coolants for superconducting field coils and/or armature windings are removed. Because of the modulation effect of the reluctance rotor between the two stators and the armature reaction field, moving AC magnetic fields are acted on superconducting coils in the inner stator. These moving AC magnetic fields are called magnetic field harmonics in the flux modulation generators. The frequencies of these harmonics are multiples of rotor mechanical frequency. Compared to synchronous superconducting generators, the amplitudes of the harmonics are higher. Even though methods to reduce the amplitudes of harmonics have been studied, the level of the AC loss in the superconducting field coils is still unknown. In this paper, numerical simulations based on the T-A formulation are used to estimate the AC loss of the superconducting field coils in a 10 MW double-stator superconducting flux modulation generator. It is found that by choosing a suitable working temperature, the AC loss of the superconducting field coils without any harmonic reduction methods is not very high, but eddy current loss of copper thermal shield inside the cryostat is significantly higher.

ACS Style

Yingzhen Liu; Jing Ou; Yi Cheng; Fabian Schreiner; Yuanzhi Zhang; Carlos Vargas-Llanos; Francesco Grilli; Ronghai Qu; Martin Doppelbauer; Mathias Noe. Investigation of AC loss of superconducting field coils in a double-stator superconducting flux modulation generator by using T-A formulation based finite element method. Superconductor Science and Technology 2021, 34, 055009 .

AMA Style

Yingzhen Liu, Jing Ou, Yi Cheng, Fabian Schreiner, Yuanzhi Zhang, Carlos Vargas-Llanos, Francesco Grilli, Ronghai Qu, Martin Doppelbauer, Mathias Noe. Investigation of AC loss of superconducting field coils in a double-stator superconducting flux modulation generator by using T-A formulation based finite element method. Superconductor Science and Technology. 2021; 34 (5):055009.

Chicago/Turabian Style

Yingzhen Liu; Jing Ou; Yi Cheng; Fabian Schreiner; Yuanzhi Zhang; Carlos Vargas-Llanos; Francesco Grilli; Ronghai Qu; Martin Doppelbauer; Mathias Noe. 2021. "Investigation of AC loss of superconducting field coils in a double-stator superconducting flux modulation generator by using T-A formulation based finite element method." Superconductor Science and Technology 34, no. 5: 055009.

Journal article
Published: 02 March 2021 in IEEE Transactions on Applied Superconductivity
Reads 0
Downloads 0

A good knowledge of material properties is a critical aspect for modeling high-temperature superconductor (HTS) devices. However, the knowledge of the electrical resistivity of coated conductors above the critical current is limited. The major challenge in characterizing this regime lies in the fact that for I>Ic, heating effects and thermal instabilities can quickly destroy the conductor if nothing is done to protect it. In previous work we extracted overcritical current data, obtained by combining fast pulsed current measurements with finite element analysis (Uniform Current (UC) model). In this work, we assessed the impact of the uncertainties of the input parameters on the quantities calculated with the UC model (temperature, current in each layer of the tape and resistivity of HTS). Firstly, sensitivity and uncertainty analyses were performed and it was found that the input parameters that mostly affect the UC model are the electrical resistivity and the thickness of the silver layer. Afterwards, an optimization method was developed to correctly estimate the geometry and the resistivity of the silver layer. This method combines experimental measurements of resistance R(T) of the tape and pulsed current measurements. The development of this strategy allowed us to determine the parameters that significantly impact the results of the UC model and helped to minimize their uncertainties. This enables a more accurate estimation of the resistivity in the overcritical current regime.

ACS Style

Nicolo Riva; Francesco Grilli; Frederic Sirois; Christian Lacroix; Arooj Akbar; Bertrand Dutoit. Optimization Method for Extracting Stabilizer Geometry and Properties of REBCO Tapes. IEEE Transactions on Applied Superconductivity 2021, 31, 1 -5.

AMA Style

Nicolo Riva, Francesco Grilli, Frederic Sirois, Christian Lacroix, Arooj Akbar, Bertrand Dutoit. Optimization Method for Extracting Stabilizer Geometry and Properties of REBCO Tapes. IEEE Transactions on Applied Superconductivity. 2021; 31 (5):1-5.

Chicago/Turabian Style

Nicolo Riva; Francesco Grilli; Frederic Sirois; Christian Lacroix; Arooj Akbar; Bertrand Dutoit. 2021. "Optimization Method for Extracting Stabilizer Geometry and Properties of REBCO Tapes." IEEE Transactions on Applied Superconductivity 31, no. 5: 1-5.

Accepted manuscript
Published: 21 January 2021 in Superconductor Science and Technology
Reads 0
Downloads 0

The development of the high-temperature superconductors (HTS) has allowed the emergence of diverse superconductor devices. Some of these devices, like wind power generators and high-field magnets, are classified as large-scale HTS systems, because they are made of several hundreds or thousands of turns of conductors. The electromagnetic analysis of such systems cannot be addressed by means of the available analytical models. The finite-element method has been extensively used to solve the H formulation of the Maxwell's equations, thus far with great success. Nevertheless, its application to large scale HTS systems is still hindered by excessive computational load. The recently proposed T-A formulation has allowed building more efficient models for systems made of HTS tapes. Both formulations have been successfully applied in conjunction with the homogenization and multi-scaling methods, these advanced methods allow reducing the required computational resources. A new advanced method, called densification, is proposed here. The most important contribution of this article is the comprehensive comparison of the strategies emerged from the combined use of the two formulations and the three advanced methods.

ACS Style

Edgar Berrospe-Juarez; Frederic Trillaud; Víctor M R Zermeño; Francesco Grilli. Advanced electromagnetic modeling of large-scale high-temperature superconductor systems based on H and T-A formulations. Superconductor Science and Technology 2021, 34, 044002 .

AMA Style

Edgar Berrospe-Juarez, Frederic Trillaud, Víctor M R Zermeño, Francesco Grilli. Advanced electromagnetic modeling of large-scale high-temperature superconductor systems based on H and T-A formulations. Superconductor Science and Technology. 2021; 34 (4):044002.

Chicago/Turabian Style

Edgar Berrospe-Juarez; Frederic Trillaud; Víctor M R Zermeño; Francesco Grilli. 2021. "Advanced electromagnetic modeling of large-scale high-temperature superconductor systems based on H and T-A formulations." Superconductor Science and Technology 34, no. 4: 044002.

Corrigendum
Published: 11 January 2021 in Superconductor Science and Technology
Reads 0
Downloads 0
ACS Style

Mark Ainslie; Francesco Grilli; Loïc Quéval; Enric Pardo; Fernando Perez-Mendez; Ratu Mataira; Antonio Morandi; Asef Ghabeli; Chris Bumby; Roberto Brambilla. Corrigendum: A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo (2020 Supercond. Sci. Technol. 33 105009). Superconductor Science and Technology 2021, 34, 029502 .

AMA Style

Mark Ainslie, Francesco Grilli, Loïc Quéval, Enric Pardo, Fernando Perez-Mendez, Ratu Mataira, Antonio Morandi, Asef Ghabeli, Chris Bumby, Roberto Brambilla. Corrigendum: A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo (2020 Supercond. Sci. Technol. 33 105009). Superconductor Science and Technology. 2021; 34 (2):029502.

Chicago/Turabian Style

Mark Ainslie; Francesco Grilli; Loïc Quéval; Enric Pardo; Fernando Perez-Mendez; Ratu Mataira; Antonio Morandi; Asef Ghabeli; Chris Bumby; Roberto Brambilla. 2021. "Corrigendum: A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo (2020 Supercond. Sci. Technol. 33 105009)." Superconductor Science and Technology 34, no. 2: 029502.

Journal article
Published: 09 January 2021 in Superconductor Science and Technology
Reads 0
Downloads 0
ACS Style

Francesco Grilli. Calculating the full-range dynamic loss of HTS wires in an instant. Superconductor Science and Technology 2021, 34, 020501 .

AMA Style

Francesco Grilli. Calculating the full-range dynamic loss of HTS wires in an instant. Superconductor Science and Technology. 2021; 34 (2):020501.

Chicago/Turabian Style

Francesco Grilli. 2021. "Calculating the full-range dynamic loss of HTS wires in an instant." Superconductor Science and Technology 34, no. 2: 020501.

Accepted manuscript
Published: 07 December 2020 in Superconductor Science and Technology
Reads 0
Downloads 0

Previous studies of test coils have demonstrated the high thermal and electrical stability of no-insulation (NI) high temperature superconductor (HTS) coils thanks to the presence of turn-to-turn current paths. These turn-to-turn current paths in a NI coil are significantly influenced by the contact resistivity. In practice, it is very challenging to measure the contact resistivity of a NI coil by direct experiments of short samples, since the contact resistivity of superconducting tapes is influenced by surface roughness and tolerance, stress, temperature etc. A proper simulation model is needed to investigate the contact resistivity of the NI coils with dedicated experiments. Hence, in this paper a distributed circuit model is employed. This model, implemented in Matlab 2018a, considers the local contact resistivity, self and mutual inductance, and HTS resistance, which depends on the supplied current, magnetic field and temperature. To validate the model, experimental results from literature, including sudden discharge, and charge-discharge processes, are employed and the results from simulations are consistent with experimental results. Then the model is used to investigate the equivalent contact resistivity of a 157-turn NI coil. Through the comparison of simulated and experimental results, it is found that the contact resistivity of the NI coil has an inhomogeneous distribution. When the current changes with different speeds, ramping rates or frequency, different number of turn-to-turn contacts carries radial current. Since the turn-to-turn contacts have different contact resistivity, the equivalent contact resistivity calculated from sudden discharge cannot be used in simulations to reproduce all the experimental data.

ACS Style

Yingzhen Liu; Jing Ou; Roland Gyuraki; Fabian Schreiner; Wescley Tiago Batista De Sousa; Mathias Noe; Francesco Grilli. Study of contact resistivity of a no-insulation superconducting coil. Superconductor Science and Technology 2020, 34, 035009 .

AMA Style

Yingzhen Liu, Jing Ou, Roland Gyuraki, Fabian Schreiner, Wescley Tiago Batista De Sousa, Mathias Noe, Francesco Grilli. Study of contact resistivity of a no-insulation superconducting coil. Superconductor Science and Technology. 2020; 34 (3):035009.

Chicago/Turabian Style

Yingzhen Liu; Jing Ou; Roland Gyuraki; Fabian Schreiner; Wescley Tiago Batista De Sousa; Mathias Noe; Francesco Grilli. 2020. "Study of contact resistivity of a no-insulation superconducting coil." Superconductor Science and Technology 34, no. 3: 035009.

Journal article
Published: 23 November 2020 in IEEE Access
Reads 0
Downloads 0

The current capacity of high-temperature superconductors (HTS) has encouraged several applications of these materials in electric power systems. These applications in electrical machines represent a promising solution for more compact and efficient designs. Despite no measurable resistance in the superconducting state, HTS could experience losses under time changing transport current or magnetic field. Therefore, loss estimation is a key input for the design. Maxwell’s equations in the T-A formulation form can be used to model and estimate losses in the superconducting tapes of an electrical machine. This formulation requires the current as a function of time in each superconducting tape as an input. A methodology to calculate this current distribution is presented in this article. The procedure introduces a previous step in the building model process and allows a better connection of the machine design with the estimation of losses in the superconductor in order to get a more efficient machine. The approach is applied to a 10 MW superconducting generator, where over one thousand tapes cross-sections are modelled in 2D. The superconductor’s non-linear behaviour and critical current density anisotropy are considered. Losses are estimated for different designs and a sensitivity analysis is presented for different temperatures and frequencies, in addition to other alternatives to reduce losses.

ACS Style

Carlos Roberto Vargas-Llanos; Sebastian Lengsfeld; Francesco Grilli. T-A Formulation for the Design and AC Loss Calculation of a Superconducting Generator for a 10 MW Wind Turbine. IEEE Access 2020, 8, 208767 -208778.

AMA Style

Carlos Roberto Vargas-Llanos, Sebastian Lengsfeld, Francesco Grilli. T-A Formulation for the Design and AC Loss Calculation of a Superconducting Generator for a 10 MW Wind Turbine. IEEE Access. 2020; 8 (99):208767-208778.

Chicago/Turabian Style

Carlos Roberto Vargas-Llanos; Sebastian Lengsfeld; Francesco Grilli. 2020. "T-A Formulation for the Design and AC Loss Calculation of a Superconducting Generator for a 10 MW Wind Turbine." IEEE Access 8, no. 99: 208767-208778.

Journal article
Published: 26 October 2020 in IEEE Transactions on Applied Superconductivity
Reads 0
Downloads 0

The H-formulation, used abundantly for the simulation of high-temperature superconductors, has shown to be a very versatile and easily implementable way of modeling electromagnetic phenomena involving superconducting materials. However, the simulation of a full vector field in current-free domains unnecessarily adds degrees of freedom to the model, thereby increasing computation times. In this contribution, we implement the well-known H- $\phi$ formulation in COMSOL multiphysics in order to compare the numerical performance of the H and H- $\phi$ formulations in the context of computing the magnetization of bulk superconductors. We show that the H- $\phi$ formulation can reduce the number of degrees of freedom and computation times by nearly a factor of two for a given relative error. The accuracy of the magnetic fields obtained with both formulations are demonstrated to be similar. The computational benefits of the H- $\phi$ formulation are shown to far outweigh the added complexity of its implementation, especially in 3-D. Finally, we identify the ideal element orders for both H and H- $\phi$ formulations to be quartic in 2-D and cubic in 3-D, corresponding to the highest element orders implementable in COMSOL.

ACS Style

Alexandre Arsenault; Frederic Sirois; Francesco Grilli. Implementation of the H-$\phi$ Formulation in COMSOL Multiphysics for Simulating the Magnetization of Bulk Superconductors and Comparison With the H-Formulation. IEEE Transactions on Applied Superconductivity 2020, 31, 1 -11.

AMA Style

Alexandre Arsenault, Frederic Sirois, Francesco Grilli. Implementation of the H-$\phi$ Formulation in COMSOL Multiphysics for Simulating the Magnetization of Bulk Superconductors and Comparison With the H-Formulation. IEEE Transactions on Applied Superconductivity. 2020; 31 (2):1-11.

Chicago/Turabian Style

Alexandre Arsenault; Frederic Sirois; Francesco Grilli. 2020. "Implementation of the H-$\phi$ Formulation in COMSOL Multiphysics for Simulating the Magnetization of Bulk Superconductors and Comparison With the H-Formulation." IEEE Transactions on Applied Superconductivity 31, no. 2: 1-11.

Journal article
Published: 14 October 2020 in Superconductor Science and Technology
Reads 0
Downloads 0
ACS Style

N Riva; F Sirois; C Lacroix; W T B de Sousa; B Dutoit; F Grilli. Resistivity of REBCO tapes in overcritical current regime: impact on superconducting fault current limiter modeling. Superconductor Science and Technology 2020, 33, 114008 .

AMA Style

N Riva, F Sirois, C Lacroix, W T B de Sousa, B Dutoit, F Grilli. Resistivity of REBCO tapes in overcritical current regime: impact on superconducting fault current limiter modeling. Superconductor Science and Technology. 2020; 33 (11):114008.

Chicago/Turabian Style

N Riva; F Sirois; C Lacroix; W T B de Sousa; B Dutoit; F Grilli. 2020. "Resistivity of REBCO tapes in overcritical current regime: impact on superconducting fault current limiter modeling." Superconductor Science and Technology 33, no. 11: 114008.

Journal article
Published: 04 September 2020 in Superconductor Science and Technology
Reads 0
Downloads 0
ACS Style

Mark Ainslie; Francesco Grilli; Loïc Quéval; Enric Pardo; Fernando Perez-Mendez; Ratu Mataira; Antonio Morandi; Asef Ghabeli; Chris Bumby; Roberto Brambilla. A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo. Superconductor Science and Technology 2020, 33, 105009 .

AMA Style

Mark Ainslie, Francesco Grilli, Loïc Quéval, Enric Pardo, Fernando Perez-Mendez, Ratu Mataira, Antonio Morandi, Asef Ghabeli, Chris Bumby, Roberto Brambilla. A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo. Superconductor Science and Technology. 2020; 33 (10):105009.

Chicago/Turabian Style

Mark Ainslie; Francesco Grilli; Loïc Quéval; Enric Pardo; Fernando Perez-Mendez; Ratu Mataira; Antonio Morandi; Asef Ghabeli; Chris Bumby; Roberto Brambilla. 2020. "A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo." Superconductor Science and Technology 33, no. 10: 105009.

Journal article
Published: 07 August 2020 in IEEE Transactions on Applied Superconductivity
Reads 0
Downloads 0

In recent years, the $H$ formulation of Maxwell's equation has become the de facto standard for simulating the time-dependent electromagnetic behavior of superconducting applications with commercial software. However, there are cases where other formulations are desirable, for example for modeling superconducting turns in electrical machines or situations where the superconductor is better described by the critical state than by a power-law resistivity. In order to accurately and efficiently handle these situations, here we consider two approaches based on the magnetic vector potential: the $T-A$ formulation of Maxwell's equations (with power-law resistivity) and the implementation of a quasi critical state model with a steep $E-J$ relationship limited at $J_{\mathrm c}$ . In this contribution, we extend the $T-A$ formulation to thick conductors so that large coils with different coupling scenarios between the turns can be considered. We also discuss the quasi critical state model in terms of its ability to calculate AC losses: in particular, we investigate the dependence of the calculated AC losses on the frequency of the AC excitation and the possibility of using quick one-step (instead of full cycle) simulations to calculate the AC losses.

ACS Style

Francesco Grilli; Enric Pardo; Antonio Morandi; Fedor Fedor Gomory; Mykola Solovyov; Victor M. R. Zermeno; Roberto Brambilla; Tara Benkel; Nicolo' Riva. Electromagnetic Modeling of Superconductors With Commercial Software: Possibilities With Two Vector Potential-Based Formulations. IEEE Transactions on Applied Superconductivity 2020, 31, 1 -9.

AMA Style

Francesco Grilli, Enric Pardo, Antonio Morandi, Fedor Fedor Gomory, Mykola Solovyov, Victor M. R. Zermeno, Roberto Brambilla, Tara Benkel, Nicolo' Riva. Electromagnetic Modeling of Superconductors With Commercial Software: Possibilities With Two Vector Potential-Based Formulations. IEEE Transactions on Applied Superconductivity. 2020; 31 (1):1-9.

Chicago/Turabian Style

Francesco Grilli; Enric Pardo; Antonio Morandi; Fedor Fedor Gomory; Mykola Solovyov; Victor M. R. Zermeno; Roberto Brambilla; Tara Benkel; Nicolo' Riva. 2020. "Electromagnetic Modeling of Superconductors With Commercial Software: Possibilities With Two Vector Potential-Based Formulations." IEEE Transactions on Applied Superconductivity 31, no. 1: 1-9.

Journal article
Published: 04 August 2020 in Superconductor Science and Technology
Reads 0
Downloads 0
ACS Style

Simon Otten; Anna Kario; Eduard Demencik; Rainer Nast; Francesco Grilli. Anisotropic monoblock model for computing AC loss in partially coupled Roebel cables. Superconductor Science and Technology 2020, 33, 094013 .

AMA Style

Simon Otten, Anna Kario, Eduard Demencik, Rainer Nast, Francesco Grilli. Anisotropic monoblock model for computing AC loss in partially coupled Roebel cables. Superconductor Science and Technology. 2020; 33 (9):094013.

Chicago/Turabian Style

Simon Otten; Anna Kario; Eduard Demencik; Rainer Nast; Francesco Grilli. 2020. "Anisotropic monoblock model for computing AC loss in partially coupled Roebel cables." Superconductor Science and Technology 33, no. 9: 094013.

Journal article
Published: 21 May 2020 in IEEE Access
Reads 0
Downloads 0

This paper reviews the modelling of high-temperature superconductors (HTS) using the finite-element method (FEM) based on the H-formulation of Maxwell’s equations. This formulation has become the most popular numerical modelling method for simulating the electromagnetic behaviour of HTS, especially thanks to the easiness of implementation in the commercial finite-element program COMSOL Multiphysics. Numerous studies prove that the H-formulation is able to simulate a wide scope of HTS topologies, from simple geometries such as HTS tapes and coils, to more complex HTS devices, up to large superconducting magnets. In this paper, we review the basics of the H-formulation, its evolution from 2D to 3D, its application for calculating critical currents and AC losses as well as magnetization of HTS bulks and tape stacks. We also review the use of the H-formulation for large-scale HTS applications, its use to solve multi-physics problems involving electromagnetic-thermal and electromagnetic-mechanical couplings, and its application to study the dynamic resistance of superconductors and flux pumps.

ACS Style

Boyang Shen; Francesco Grilli; Tim Coombs. Overview of H-Formulation: A Versatile Tool for Modeling Electromagnetics in High-Temperature Superconductor Applications. IEEE Access 2020, 8, 100403 -100414.

AMA Style

Boyang Shen, Francesco Grilli, Tim Coombs. Overview of H-Formulation: A Versatile Tool for Modeling Electromagnetics in High-Temperature Superconductor Applications. IEEE Access. 2020; 8 (99):100403-100414.

Chicago/Turabian Style

Boyang Shen; Francesco Grilli; Tim Coombs. 2020. "Overview of H-Formulation: A Versatile Tool for Modeling Electromagnetics in High-Temperature Superconductor Applications." IEEE Access 8, no. 99: 100403-100414.

Accepted manuscript
Published: 06 May 2020 in European Journal of Physics
Reads 0
Downloads 0

A numerical model implemented in the finite-element method open-source FreeFEM program is presented, with the aim of introducing students to the calculation of AC losses in superconductors. With this simple approach, students can learn about the critical state model used to describe the macroscopic electromagnetic behavior of superconductors and the importance of several factors influencing the AC losses of superconductors.

ACS Style

Francesco Grilli; Enrico Rizzo. A numerical model to introduce students to AC loss calculation in superconductors. European Journal of Physics 2020, 41, 045203 .

AMA Style

Francesco Grilli, Enrico Rizzo. A numerical model to introduce students to AC loss calculation in superconductors. European Journal of Physics. 2020; 41 (4):045203.

Chicago/Turabian Style

Francesco Grilli; Enrico Rizzo. 2020. "A numerical model to introduce students to AC loss calculation in superconductors." European Journal of Physics 41, no. 4: 045203.

Journal article
Published: 10 March 2020 in IEEE Transactions on Applied Superconductivity
Reads 0
Downloads 0

Screening currents have long been known to impact the stress state in tape-wound superconducting coils. In recent years the advent of REBCO tape has led to the development of tape-wound coils by a number of organizations. While several groups have been computing screening currents and ac losses in REBCO tape in a variety of applications for several years, little has been published about the stress due to the screening currents. This problem is challenging due to the need to analyze thousands of REBCO turns which are not bonded together. The T-A formulation of Maxwell's equations employing a homogenization technique enables efficient estimation of the current distribution while structural calculations employing contact elements allow conservative estimation of stresses. Computational results are compared with observed degradation in a test coil. Future coil designs that include the effects of screening current strains are proposed

ACS Style

Dylan J Kolb-Bond; Edgar Berrospe-Juarez; Mark Bird; Iain R. Dixon; Hubertus W. Weijers; Frederic Trillaud; Victor M. R. Zermeno; Francesco Grilli. Computing Strains Due to Screening Currents in REBCO Magnets. IEEE Transactions on Applied Superconductivity 2020, 30, 1 -5.

AMA Style

Dylan J Kolb-Bond, Edgar Berrospe-Juarez, Mark Bird, Iain R. Dixon, Hubertus W. Weijers, Frederic Trillaud, Victor M. R. Zermeno, Francesco Grilli. Computing Strains Due to Screening Currents in REBCO Magnets. IEEE Transactions on Applied Superconductivity. 2020; 30 (4):1-5.

Chicago/Turabian Style

Dylan J Kolb-Bond; Edgar Berrospe-Juarez; Mark Bird; Iain R. Dixon; Hubertus W. Weijers; Frederic Trillaud; Victor M. R. Zermeno; Francesco Grilli. 2020. "Computing Strains Due to Screening Currents in REBCO Magnets." IEEE Transactions on Applied Superconductivity 30, no. 4: 1-5.

Review
Published: 12 February 2020 in Superconductor Science and Technology
Reads 0
Downloads 0
ACS Style

Boyang Shen; Francesco Grilli; Tim Coombs. Review of the AC loss computation for HTS using H formulation. Superconductor Science and Technology 2020, 33, 033002 .

AMA Style

Boyang Shen, Francesco Grilli, Tim Coombs. Review of the AC loss computation for HTS using H formulation. Superconductor Science and Technology. 2020; 33 (3):033002.

Chicago/Turabian Style

Boyang Shen; Francesco Grilli; Tim Coombs. 2020. "Review of the AC loss computation for HTS using H formulation." Superconductor Science and Technology 33, no. 3: 033002.