Publications

Export 9 results:
Sort by: [ Author  (Asc)] Title Type Year
A B C D E F G H [I] J K L M N O P Q R S T U V W X Y Z   [Show ALL]
I
Inácio, David, João Pina, Anabela Gonçalves, Mário Neves, and Amadeu Rodrigues. "Numerical and Experimental Comparison of Electromechanical Properties and Efficiency of HTS and Ferromagnetic Hysteresis Motors." 8th European Conference on Applied Superconductivity (EUCAS). 2007. 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'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's non-linear magnetic properties, while in HTS materials the hysteresis has an ohmic nature and is related with vortices' 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's electromechanical performances but also the overall systems efficiency, including cryogenics for the HTS device.

Inácio, David Comparação numérica e experimental das características dos Motores de Histerese Convencional e Supercondutor. Eds. Mário Neves, Anabela Gonçalves, and João Pina. FCT-UNL, 2008. Abstract

Os motores de histerese são muito atraentes, numa ampla gama de aplicações devido à característica binário - velocidade e simplicidade de construção. É esperado que o rendimento destes motores seja melhorado aquando do uso de materiais supercondutores de alta temperatura (SAT ? supercondutores de alta temperatura) e, de facto, os motores de histerese têm-se mostrado como, provavelmente, a melhor máquina eléctrica usando materiais SAT. Ambos os motores, quer convencional quer supercondutor (com SAT), são motores de histerese, mas apresentam diferentes fenómenos físicos para o seu funcionamento: o comportamento de histerese nos materiais ferromagnéticos convencionais é devido à falta de linearidade das suas propriedades magnéticas dos materiais ferromagnéticos enquanto a histerese nos materiais supercondutores de alta temperatura é de natureza ohmica e está relacionada com dinâmica de vórtices. Nesta tese aspectos teóricos, experimentais e simulados de ambos os motores são discutidos, realçando-se o princípio de funcionamento de cada um e as características mais relevantes de cada um. As características obtidas, quer por testes experimentais quer por uso do simulador usando elementos finitos (FLUX2D?), foram comparadas com o objectivo de avaliar o rendimento dos motores electromecânicos e a eficiência dos sistemas, incluindo a criogenia para os dispositivos supercondutores de alta temperatura.

Inácio, D., João Pina, Go{\cn}alo Luis, J. F. Martins, M. Ventim-Neves, and Alfredo Alvarez. "Experimental Characterization of a Conventional (Aluminum) and of a Superconducting (YBCO) Axial Flux Disc Motor." IEEE Transactions on Applied Superconductivity (2011). AbstractWebsite

An equivalent model and electromechanical characteristics for the disk motor was obtained based on the Steinmetz parameters. This paper describes a series of tests conducted on an axial flux motor, equipped with an aluminum rotor disc and an YBCO high temperature superconducting rotor disc, at liquid nitrogen temperature (77 K). The rotating magnetic field was produced by a four-pole, three-phase stator winding, at 50 Hz. At asynchronous permanent regime, Steinmetz-type models are able to describe both motors' behavior. From the performed tests, the parameters of both motors' models were deduced. A variable load was used to obtain both motor's characteristics (conventional and superconducting). Experimental obtained characteristics of both motors are compared with the ones predicted from parameters' calculation. The HTS motor provides high efficiency then the conventional ones.

Inácio, S., D. Inácio, J. Pina, S. Valtchev, Ventim M. Neves, and A. Rodrigues. "An Electrical Gearbox by means of pole variation for induction and superconducting disc motor." 8th European Conference on Applied Superconductivity (EUCAS). 2007. 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'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'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' 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.

Inácio, Steve Projecto de uma caixa de velocidades eléctrica por meio da variação do número de pólos para motores em disco de rotor em alumínio e em materiais supercondutores de alta temperatura (SAT). Eds. Mário Neves, João Pina, and Stanimir Valtchev. FCT-UNL, 2008. Abstract

Nesta dissertação apresenta-se um motor em disco polifásico inovador bem como uma estratégia de controlo com base no método de variação de velocidade por comutação do número de pares de pólos. A configuração das bobinas aliada à escolha das correntes e tensões que se injectam nas bobinas dos estatores, permite comutar electronicamente o número de pólos do motor entre 2, 4 6 e 8 pólos, conseguindo-se controlar a característica binário?velocidade do motor. O motor em disco possui a bobinagem feita em cobre com dois semi-estatores, em que quando utiliza o rotor em alumínio (com condutividade diferente de zero) comporta-se como um motor de indução convencional. Quando se substitui o rotor em alumínio por um constituído por um supercondutor de alta temperatura (SAT), o dispositivo comporta-se como um motor de histerese. O princípio de funcionamento do motor em disco convencional é baseado na indução de força electromotrizes no rotor e, consequentemente, uma vez que o alumínio é bom condutor eléctrico, correntes eléctricas induzidas, originadas por haver um campo magnético variável que é criado pelos semi-estatores. O comportamento deste tipo de motores, no que diz respeito a principais características (como o binário?velocidade para os diferentes números de pares de pólos), circuito equivalente de Steinmetz, entre outras teorias associadas é já conhecido há bastante tempo. O princípio de funcionamento do motor SAT é diferente do apresentado anteriormente, funciona com base na dinâmica de vórtices e devido ao facto de aparecer o fenómeno de ancoragem de fluxo (flux pinning) nos supercondutores de alta temperatura. Como o campo magnético varia, então o disco roda. Este motor tem um princípio de funcionamento muito mais complexo que o motor de indução sendo a obtenção do modelo do motor SAT complicada. A obtenção do modelo do motor SAT não é abordado nesta dissertação. Os comportamentos e modos de operação do motor com disco de alumínio e em materiais SAT são simulados através de um programa comercial de elementos finitos, nesta dissertação, sendo a supercondutividade simulada com base na relação entre o campo eléctrico e a densidade de corrente pela lei da potenciação (E-J power law). Com as simulações pretende-se comparar o rendimento electromecânico de ambos os motores.

Inácio, David, João Pina, Go{\cn}alo Luis, João F. Martins, Mário Neves, and Alfredo Alvarez. "Experimental Characterization of a Conventional (Aluminum) and of a Superconducting (YBCO) Axial Flux Disc Motor." IEEE Transactions on Applied Superconductivity. 21 (2011): 1146-1150. AbstractWebsite

An equivalent model and electromechanical characteristics for the disk motor was obtained based on the Steinmetz parameters. This paper describes a series of tests conducted on an axial flux motor, equipped with an aluminum rotor disc and an YBCO high temperature superconducting rotor disc, at liquid nitrogen temperature (77 K). The rotating magnetic field was produced by a four-pole, three-phase stator winding, at 50 Hz. At asynchronous permanent regime, Steinmetz-type models are able to describe both motors' behavior. From the performed tests, the parameters of both motors' models were deduced. A variable load was used to obtain both motor's characteristics (conventional and superconducting). Experimental obtained characteristics of both motors are compared with the ones predicted from parameters' calculation. The HTS motor provides high efficiency then the conventional ones.

Inácio, S., D. Inácio, J. M. Pina, Stanimir Valtchev, M. V. Neves, and A. L. Rodrigues. "An electrical gearbox by means of pole variation for induction and superconducting disc motor." Journal of Physics: Conference Series. 97 (2008): 012221. AbstractWebsite

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'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'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' 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.

Inácio, D., J. A. Inácio, J. Pina, S. Valtchev, M. Neves, J. Martins, and A. Rodrigues. "Conventional and HTS Disc motor with pole variation control." 2nd International Conference on Power Engineering, Energy and Electrical Drives (POWERENG'2009). 2009. 513-518. 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'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'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' 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's computed are compared. Considerations about the systems overall efficiency, including cryogenics, are also discussed.

Inácio, David, João Pina, João Martins, Mário Ventim Neves, and Alfredo Álvarez. "Lumped Parameters Equivalent Circuit of a Superconducting Hysteresis Motor." EUCAS Conference 2011. Vol. 36. 2012. 975-979. Abstract

The potential advantage of using superconducting materials in electrical devices is well described in the literature. The electromagnetic properties of these materials make them unique for several applications, such as, e.g. electrical machines and drives, fault current applications, or superconducting magnetic energy storage. In the development of electromechanical conversion devices, superconducting materials are used foreseeing mainly a decrease in the device dimensions or a performance improvement for the same active volume. To guarantee a good application of this kind of materials it is important to describe and model the phenomena that characterize their operation under different regimes. In this paper, a study based in FEM simulations of a motor with bulk superconductor in the rotor is carried out, with the purpose of understand, quantify and qualify which phenomena are present in the different regimes of the motor, leading to obtaining an equivalent electrical circuit with lumped parameters.