@conference {OA881, title = {Case Study in the Design of HTS Machines: an All Superconducting Linear Synchronous Motor}, booktitle = {1st International Conference on Power Engineering, Energy and Electrical Drives, POWERENG}, year = {2007}, note = {n/a}, month = {April}, pages = {185{\textendash}190}, abstract = {

The electric and magnetic properties of high temperature superconductors and the possibility to cool them by cheap liquid nitrogen makes them attractive in power applications. An all superconducting linear synchronous motor is presented in this paper in order to quantify the benefits and disadvantages of such applications. The term ?all superconducting? is related with the absence of copper conductors and iron parts. Certain characteristics of the superconducting materials impose severe restrictions when used, e.g., as armature windings. A numerical method for deriving the thrust and lift forces developed in such a motor, driven by a typical current inverter, is presented.

}, keywords = {High Temperature Superconductivity, Ironless Linear Motor, superconducting machines}, url = {http://oa.uninova.pt/881/}, author = {Jo{\~a}o Pina and M{\'a}rio Neves and Amadeu Rodrigues} } @conference {OA1789, title = {Conventional and HTS Disc motor with pole variation control}, booktitle = {2nd International Conference on Power Engineering, Energy and Electrical Drives (POWERENG{\textquoteright}2009)}, year = {2009}, note = {n/a}, pages = {513{\textendash}518}, abstract = {

In this paper, a poly-phase disc motor innovative feeding and control strategy, based on a variable poles approach, and its application to a high temperature superconductor (HTS) disc motor, are presented. The stator windings may be electronically commutated to implement a 2, 4, 6 or 8 poles winding, thus changing the motor{\textquoteright}s torque?speed characteristics. The motor may be a conventional induction motor with a conductive disc rotor, or a new HTS disc motor, with conventional copper windings at its two iron semi-stators and a HTS disc as a rotor. The conventional induction motor{\textquoteright}s operation principle is related with the induced electromotive forces in the conductive rotor. Its behaviour, characteristics and modelling through Steinmetz and others theories are well known. The operation principle of the motor with HTS rotor, however, is rather different and is related with vortices{\textquoteright} dynamics and pinning characteristics; this is a much more complex process than induction, and its modelling is quite complicated. In this paper, the operation was simulated through finite-elements commercial software (FLUX2D), whereas superconductivity was simulated by the E-J power law. The electromechanical performance of both motor{\textquoteright}s computed are compared. Considerations about the systems overall efficiency, including cryogenics, are also discussed.

}, url = {http://oa.uninova.pt/1789/}, author = {D In{\'a}cio and J. A. In{\'a}cio and J. Pina and S Valtchev and M. Neves and J. Martins and A. Rodrigues} } @article {OA352, title = {Design of a Linear Synchronous Motor With High Temperature Superconductor Materials in the Armature and in the Field Excitation System}, journal = {Journal of Physics: Conference Series}, volume = {43}, year = {2006}, note = {n/a}, pages = {804{\textendash}808}, publisher = {IOP}, abstract = {n/a}, url = {http://oa.uninova.pt/352/}, author = {Jo{\~a}o Pina and M{\'a}rio Neves and M. McCulloch and Amadeu Rodrigues} } @conference {OA354, title = {Design of a Linear Synchronous Motor With High Temperature Superconductor Materials in the Armature and in the Field Excitation System}, booktitle = {European Conference on Applied Superconductivity, EUCAS?05}, year = {2005}, note = {n/a}, month = {September}, abstract = {n/a}, url = {http://oa.uninova.pt/354/}, author = {Jo{\~a}o Pina and M{\'a}rio Neves and M. McCulloch and Amadeu Rodrigues} } @article {OA1764, title = {An electrical gearbox by means of pole variation for induction and superconducting disc motor}, journal = {Journal of Physics: Conference Series}, volume = {97}, year = {2008}, note = {n/a}, pages = {012221}, abstract = {

In this paper, a poly-phase disc motor innovative feeding and control strategy, based on a variable poles approach, and its application to a HTS disc motor, are presented. The stator windings may be electronically commutated to implement a 2, 4, 6 or 8 poles winding, thus changing the motor{\textquoteright}s torque?speed characteristics. The motor may be a conventional induction motor with a conductive disc rotor, or a new HTS disc motor, with conventional copper windings at its two iron semi-stators, and a HTS disc as a rotor. The conventional induction motor{\textquoteright}s operation principle is related with the induced electromotive forces in the conductive rotor. Its behaviour, characteristics (namely their torque?speed characteristics for different number of pole pairs) and modelling through Steinmetz and others theories are well known. The operation principle of the motor with HTS rotor, however, is rather different and is related with vortices{\textquoteright} dynamics and pinning characteristics; this is a much more complex process than induction, and its modelling is quite complicated. In this paper, the operation was simulated through finite-elements commercial software, whereas superconductivity was simulated by the E-J power law. The Electromechanical performances of both motors where computed and are presented and compared. Considerations about the systems overall efficiency, including cryogenics, are also discussed.

}, url = {http://oa.uninova.pt/1764/}, author = {S In{\'a}cio and D In{\'a}cio and J M Pina and Stanimir Valtchev and M V Neves and A L Rodrigues} } @conference {OA1792, title = {An Electrical Gearbox by means of pole variation for induction and superconducting disc motor}, booktitle = {8th European Conference on Applied Superconductivity (EUCAS)}, year = {2007}, note = {n/a}, abstract = {

In this paper, a poly-phase disc motor innovative feeding and control strategy, based on a variable poles approach, and its application to a HTS disc motor, are presented. The stator windings may be electronically commutated to implement a 2, 4, 6 or 8 poles winding, thus changing the motor{\textquoteright}s torque?speed characteristics. The motor may be a conventional induction motor with a conductive disc rotor, or a new HTS disc motor, with conventional copper windings at its two iron semi-stators, and a HTS disc as a rotor. The conventional induction motor{\textquoteright}s operation principle is related with the induced electromotive forces in the conductive rotor. Its behaviour, characteristics (namely their torque?speed characteristics for different number of pole pairs) and modelling through Steinmetz and others theories are well known. The operation principle of the motor with HTS rotor, however, is rather different and is related with vortices{\textquoteright} dynamics and pinning characteristics; this is a much more complex process than induction, and its modelling is quite complicated. In this paper, the operation was simulated through finite-elements commercial software, whereas superconductivity was simulated by the E-J power law. The Electromechanical performances of both motors where computed and are presented and compared. Considerations about the systems overall efficiency, including cryogenics, are also discussed.

}, url = {http://oa.uninova.pt/1792/}, author = {S In{\'a}cio and D In{\'a}cio and J. Pina and S Valtchev and M Ventim Neves and A. Rodrigues} } @unpublished {OA2153, title = {Energia nuclear no panorama nacional: benef{\'\i}cios vs custos e an{\'a}lise de sustentabilidade}, year = {2009}, note = {n/a}, month = {May}, publisher = {FCT-UNL}, abstract = {n/a}, url = {http://oa.uninova.pt/2153/}, author = {Jer{\'o}nimo Cunha}, editor = {Amadeu Rodrigues and Jo{\~a}o Pina} } @article {OA359, title = {Flux Modelling of Reluctance Machines with Bulk Superconducting Materials}, journal = {Electromotion Review}, year = {2003}, note = {n/a}, abstract = {n/a}, url = {http://oa.uninova.pt/359/}, author = {Athanasis Sfetsos and Jo{\~a}o Pina and Anabela Gon{\c c}alves and M{\'a}rio Neves and Amadeu Rodrigues} } @conference {OA1769, title = {Fuel Cells as Clean Electrical Energy Sources}, booktitle = {XCLEEE - X Portuguese-Spanish Conference in Electrical Engineering}, year = {2007}, note = {n/a}, abstract = {n/a}, url = {http://oa.uninova.pt/1769/}, author = {A. Rodrigues and M{\'a}rio Neves and Jo{\~a}o Pina} } @conference {OA1773, title = {High Performance, Environment Friendly, Modular and Fault Tolerant Renewable Energy Microgrid}, booktitle = {12th International Energy Conference \& Exhibition (ENERGEX2007)}, year = {2007}, note = {n/a}, abstract = {n/a}, url = {http://oa.uninova.pt/1773/}, author = {Jo{\~a}o Pina and C. Caracaleanu and A Gon{\c c}alves and Pedro Pereira and S Valtchev and M{\'a}rio Neves and A. Rodrigues} } @conference {OA1950, title = {High Temperature Superconducting Fault Current Limiters as Enabling Technology in Electrical Grids with Increased Distributed Generation Penetration}, booktitle = {Doctoral Conference on Computing, Electrical and Industrial Systems - DoCEIS{\textquoteright}10}, year = {2010}, note = {n/a}, month = {February}, pages = {427{\textendash}434}, abstract = {

Amongst applications of high temperature superconductors, fault current limiters are foreseen as one of the most promising in power systems. Several topologies have been developed in the last years, taking advantage of different superconductors? properties. Increasing distributed generation (DG) penetration, based on renewable energy, adds new short-circuit sources to electrical grids, which brings several energy quality and protection issues. Superconducting fault current limiters can obviate these problems, representing thus an enabling technology for DG penetration. In this paper current limiter topologies are presented, its operations principles, strengths and weaknesses, in the context of these DG grids. In the end, future trends are discussed.

}, url = {http://oa.uninova.pt/1950/}, author = {Jo{\~a}o Pina and M{\'a}rio Neves and Alfredo {\'A}lvarez and Amadeu Rodrigues} } @conference {OA790, title = {Magnetisation System and Thrust Force Measurement of an All Superconducting Linear Synchronous Motor}, booktitle = {X Portuguese-Spanish Congress in Electrical Engineering}, year = {2007}, note = {n/a}, abstract = {n/a}, url = {http://oa.uninova.pt/790/}, author = {Jo{\~a}o Pina and M{\'a}rio Neves and Alfredo {\'A}lvarez and Amadeu Rodrigues} } @conference {OA1045, title = {Numerical and Experimental Comparison of Electromechanical Properties and Efficiency of HTS and Ferromagnetic Hysteresis Motors}, booktitle = {8th European Conference on Applied Superconductivity (EUCAS)}, year = {2007}, note = {n/a}, month = {September}, abstract = {

Hysteresis motors are very attractive in a wide range of fractional power applications, due to its torque-speed characteristics and simplicity of construction. This motor{\textquoteright}s performance is expected to improve when HTS rotors are used, and in fact, hysteresis motors have shown to be probably the most viable electrical machines using HTS materials. While these motors, either conventional or HTS, are both hysteresis motors, they base their operation on different physical phenomena: hysteretic behaviour in conventional ferromagnetic materials is due to the material{\textquoteright}s non-linear magnetic properties, while in HTS materials the hysteresis has an ohmic nature and is related with vortices{\textquoteright} dynamics. In this paper, theoretical aspects of both conventional and HTS hysteresis motors are discussed, its operation principles are highlighted, and the characteristics of both motors are presented. The characteristics, obtained both by experimental tests and numerical simulation (made with commercial software), are compared, in order to evaluate not only the motor{\textquoteright}s electromechanical performances but also the overall systems efficiency, including cryogenics for the HTS device.

}, url = {http://oa.uninova.pt/1045/}, author = {David In{\'a}cio and Jo{\~a}o Pina and Anabela Gon{\c c}alves and M{\'a}rio Neves and Amadeu Rodrigues} } @conference {OA5158, title = {Numerical Design Methodology for an All Superconducting Linear Synchronous Motor}, booktitle = {Technological Innovation for Sustainability}, series = {IFIP Advances in Information and Communication Technology}, volume = {349}, year = {2011}, note = {n/a}, pages = {553{\textendash}562}, abstract = {

One potential advantage of the application of superconducting materials in electrical machines is the possibility to build lighter and compact devices by removing iron. These machines find applications, e.g., in systems where cryogenics is already available, or in naturally cryogenic environments. The design of motors with high temperature superconductors (HTS) presents issues unconsidered in classical machines, besides considerations on cryogenics, such as HTS brittleness or mechanical restrictions. Moreover, HTS{\textquoteright} electromagnetic properties also degrade due to flux density components, which arise if there is no iron to guide magnetic flux. Several aspects must thus be considered in the design stage, as applications may turn less attractive or even unfeasible. In this paper these issues are detailed, and a numerical methodology for the design of an all superconducting (without iron or conventional conductors) linear synchronous motor is presented.

}, url = {http://oa.uninova.pt/5158/}, author = {Jo{\~a}o Pina and M{\'a}rio Ventim Neves and Alfredo {\'A}lvarez and Amadeu Le{\~a}o Rodrigues} } @conference {OA792, title = {Pilhas de Combust{\'\i}vel como Fonte Limpa de Energia El{\'e}ctrica}, booktitle = {X Portuguese-Spanish Congress in Electrical Engineering}, year = {2007}, note = {n/a}, abstract = {n/a}, url = {http://oa.uninova.pt/792/}, author = {Amadeu Rodrigues and M{\'a}rio Neves and Jo{\~a}o Pina} } @article {OA1816, title = {Power electronics performance in cryogenic environment: evaluation for use in HTS power devices}, journal = {Journal of Physics: Conference Series}, volume = {97}, year = {2008}, note = {n/a}, pages = {012219}, publisher = {iopscience}, abstract = {

Power electronics (PE) plays a major role in electrical devices and systems, namely in electromechanical drives, in motor and generator controllers, and in power grids, including high-voltage DC (HVDC) power transmission. PE is also used in devices for the protection against grid disturbances, like voltage sags or power breakdowns. To cope with these disturbances, back-up energy storage devices are used, like uninterruptible power supplies (UPS) and flywheels. Some of these devices may use superconductivity. Commercial PE semiconductor devices (power diodes, power MOSFETs, IGBTs, power Darlington transistors and others) are rarely (or never) experimented for cryogenic temperatures, even when designed for military applications. This means that its integration with HTS power devices is usually done in the hot environment, raising several implementation restrictions. These reasons led to the natural desire of characterising PE under extreme conditions, e. g. at liquid nitrogen temperatures, for use in HTS devices. Some researchers expect that cryogenic temperatures may increase power electronics{\textquoteright} performance when compared with room-temperature operation, namely reducing conduction losses and switching time. Also the overall system efficiency may increase due to improved properties of semiconductor materials at low temperatures, reduced losses, and removal of dissipation elements. In this work, steady state operation of commercial PE semiconductors and devices were investigated at liquid nitrogen and room temperatures. Performances in cryogenic and room temperatures are compared. Results help to decide which environment is to be used for different power HTS applications.

}, url = {http://oa.uninova.pt/1816/}, author = {P Pereira and S Valtchev and J. Pina and A Gon{\c c}alves and M Ventim Neves and A L Rodrigues} } @conference {OA1044, title = {Power Electronics Performance in Cryogenic Environment: Evaluation for Use in HTS Power Devices}, booktitle = {8th European Conference on Applied Superconductivity (EUCAS)}, year = {2007}, note = {n/a}, month = {September}, abstract = {

Power electronics (PE) plays a major role in electrical devices and systems, namely in electromechanical drives, in motor and generator controllers, and in power grids, including high-voltage DC (HVDC) power transmission. PE is also used in devices for the protection against grid disturbances, like voltage sags or power breakdowns. To cope with these disturbances, back-up energy storage devices are used, like uninterruptible power supplies (UPS) and flywheels. Some of these devices may use superconductivity. Commercial PE semiconductor devices (power diodes, power MOSFETs, IGBTs, power Darlington transistors and others) are rarely (or never) experimented for cryogenic temperatures, even when designed for military applications. This means that its integration with HTS power devices is usually done in the hot environment, raising several implementation restrictions. These reasons led to the natural desire of characterising PE under extreme conditions, e. g. at liquid nitrogen temperatures, for use in HTS devices. Some researchers expect that cryogenic temperatures may increase power electronics{\textquoteright} performance when compared with room-temperature operation, namely reducing conduction losses and switching time. Also the overall system efficiency may increase due to improved properties of semiconductor materials at low temperatures, reduced losses, and removal of dissipation elements. In this work, steady state operation of commercial PE semiconductors and devices were investigated at liquid nitrogen and room temperatures. Performances in cryogenic and room temperatures are compared. Results help to decide which environment is to be used for different power HTS applications

}, url = {http://oa.uninova.pt/1044/}, author = {Pedro Pereira and S Valtchev and Jo{\~a}o Pina and Anabela Gon{\c c}alves and M{\'a}rio Neves and Amadeu Rodrigues} } @article {OA2534, title = {Research and Development of Alternative Concepts in HTS Machines}, journal = {IEEE Transactions on Applied Superconductivity}, volume = {21}, number = {3}, year = {2010}, note = {n/a}, month = {December}, pages = {1141{\textendash}1145}, publisher = {IEEE}, abstract = {

High temperature superconducting (HTS) machines are recognized to offer several advantageous features when comparing to conventional ones. Amongst these, highlights the decrease in weight and volume of the machines, due to increased current density in conductors or the absence of iron slots{\textquoteright} teeth; or the decrease in AC losses and consequent higher efficiency of the machines, even accounting for cryogenics. These concepts have been already demonstrated and some machines have even achieved commercial stage. In this paper, several alternative approaches are applied to electrical motors employing HTS materials. The first one is an all superconducting linear motor, where copper conductors and permanent magnets are replaced by Bi-2223 windings and trapped flux magnets, taking advantage of stable levitation due to flux pinning, higher current densities and higher excitation field. The second is an induction disk motor with Bi-2223 armature, where iron, ironless and hybrid approaches are compared. Finally, an innovative command strategy, consisting of an electronically variable pole pairs{\textquoteright} number approach, is applied to a superconducting hysteresis disk motor. All these concepts are being investigated and simulation and experimental results are presented.

}, url = {http://oa.uninova.pt/2534/}, author = {Jo{\~a}o Pina and David In{\'a}cio and Gon{\c c}alo Luis and Jos{\'e} M. Ceballos and Pedro Pereira and Martins, Jo{\~a}o and Ventim-Neves, M. and Alfredo Alvarez and A. Le{\~a}o Rodrigues} } @article {OA2428, title = {Reverse engineering of inductive fault current limiters}, journal = {Journal of Physics: Conference Series}, volume = {234}, number = {3}, year = {2010}, note = {n/a}, pages = {1{\textendash}9}, publisher = {IOP Publishing}, abstract = {

The inductive fault current limiter is less compact and harder to scale to high voltage networks than the resistive one. Nevertheless, its simple construction and mechanical robustness make it attractive in low voltage grids. Thus, it might be an enabling technology for the advent of microgrids, low voltage networks with dispersed generation, controllable loads and energy storage. A new methodology for reverse engineering of inductive fault current limiters based on the independent analysis of iron cores and HTS cylinders is presented in this paper. Their electromagnetic characteristics are used to predict the devices{\textquoteright} hysteresis loops and consequently their dynamic behavior. Previous models based on the separate analysis of the limiters{\textquoteright} components were already derived, e.g. in transformer like equivalent models. Nevertheless, the assumptions usually made may limit these models{\textquoteright} application, as shown in the paper. The proposed methodology obviates these limitations. Results are validated through simulations.

}, url = {http://oa.uninova.pt/2428/}, author = {J M Pina and P Su{\'a}rez and M Ventim Neves and A {\'A}lvarez and A L Rodrigues} } @conference {OA789, title = {Study in the Design of HTS Machines: an All Superconducting Linear Synchronous Motor}, booktitle = {POWERENG 2007 - International Conference on Power Engineering, Energy and Electrical Drives}, year = {2007}, note = {n/a}, abstract = {n/a}, url = {http://oa.uninova.pt/789/}, author = {Jo{\~a}o Pina and M{\'a}rio Neves and Amadeu Rodrigues} } @conference {OA1813, title = {A test rig for thrust force measurements f an all HTS linear synchronous motor}, booktitle = {8th European Conference on Applied Superconductivity (EUCAS)}, year = {2007}, note = {n/a}, abstract = {

This paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductor{\textquoteright}s ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.

}, url = {http://oa.uninova.pt/1813/}, author = {Jo{\~a}o Pina and Pedro Pereira and S Valtchev and A Gon{\c c}alves and M{\'a}rio Neves and A. Rodrigues} } @article {OA1817, title = {A test rig for thrust force measurements of an all HTS linear synchronous motor}, journal = {Journal of Physics: Conference Series}, volume = {97}, year = {2008}, note = {n/a}, pages = {012220}, publisher = {IOPScience}, abstract = {

This paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductor{\textquoteright}s ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.

}, url = {http://oa.uninova.pt/1817/}, author = {J. Pina and P Pereira and S Valtchev and A Gon{\c c}alves and M Ventim Neves and A Alvarez and L Rodrigues} } @conference {OA791, title = {Topology of an Electrical Gearbox with Variable Poles for Induction and Superconducting Disc Motors}, booktitle = {X Portuguese-Spanish Congress in Electrical Engineering}, year = {2007}, note = {n/a}, abstract = {n/a}, url = {http://oa.uninova.pt/791/}, author = {In{\'a}cio Steve and Jo{\~a}o Pina and Stanimir Valtchev and M{\'a}rio Neves and Amadeu Rodrigues} } @article {OA360, title = {Torque Modelling of a Superconducting Reluctance Machine}, journal = {Electromotion Review}, year = {2003}, note = {n/a}, abstract = {n/a}, url = {http://oa.uninova.pt/360/}, author = {Amadeu Rodrigues and B. A. Potter and Jo{\~a}o Pina and Anabela Gon{\c c}alves and M{\'a}rio Neves} }