Light rail Maglev with superconductor materials: system design

Transcription

1 Light rail Maglev with superconductor materials: system design G. ~'~vidio', G. ~anzara', F. crisi2, A. IVavarra2 & M. villani3 I Transportation Department, University of L'Aquila, Italy 2~ceince and Technology Park of Abruzzo, L'Aquila, Italy 3~epartment of Electrical Engineering, University of L'Aquila, Italy Abstract An innovative Light Rail Maglev (LRM) is studied and proposed in order to obtain simultaneously the levitation, propulsion and guidance of vehicle and realize environmentally options for public urban transportation. The system used is a short vehicle supported by magnetic forces by using High Temperature Superconductor (HTSC) materials. The primary with HTSC wires are installed on the vehicle while the HTSC passive secondary stripes are distributed on bottom and lateral sides of guideway. The main characteristics of the proposed system are presented and discussed. 1 Maglev system in the contest of urban transport It is well known that the Light Rail transportation system is characterized by a medium transport capacity and a good flexibility in the offer, due to the easily assembling of the convoys, the bi-directionality and high frequency of work. Unfortunately, one of the main problems in the use of this system, in high urbanized area, is given by the problematic related to the environment noise during the travelling. Particularly, we refer to the acoustic noise and above all to the problem connected to the propagation of the dynamic stresses: these are due to the contact between wheel and track and depend by the number of frequency of transits, speed and weight of the vehicles.

2 658 Urban Tramport and the Ei~~~~,nrzrnatlr it? rha 21st Canrurv These stresses, interacting dangerously with the structures of buildings located nearby the vehicles transit way, affect heavily the employment of these transport systems above all in the architectonic cities of historical monuments type. At present, the problem has been solved making deep tunnels respect the surface, giving high costs as regard the making of infrastructure or, alternatively, changing the "optimal path, influencing the system efficiency. In order to solve these problems, an innovative light rail system is proposed that is based on the electromagnetic interactions for the traction and levitation of the vehicle. In fact, the possibility to transmit the normal and tangential thrust without physic contact, like as the wheel-track one, allows to reduce significantly both the acoustic noise and the transmission of the dynamic stresses on the nearest environment. The topology used is a short vehicle mounted linear primary and long track secondary. With reference to the traction, electromagnetic propulsion is less efficient than an equivalent rotary machine. For a transit operator, the aim is not the efficiency but the operating costs or more accurately the energy cost per passenger km. A vehicle with electromagnetic propulsion should be compared with a vehicle of different technology that provides the same passenger throughput and service availability. A rail vehicle with rotary drive may need more axles to achieve the same services level and availability under adverse adhesion conditions; its higher weight results in higher energy consumption. A rubber-tired system has a higher rolling resistance and requires higher energy consumption; on the contrary linear induction propulsion ideally meets the operating requirements, providing adhesion-independent transmission of acceleration and brake forces. Existing system have grades up to 6.5%; higher grades are possible [l]. The elimination of all rotating parts, gears and coupling reduce rolling resistance, equivalent rotating mass, maintenance costs and noise. The proposed system derives from analyses and experimental tests [2, 3, 41 that have been carried out in the research laboratory "Innovative Technologies for Transport" realized thanks to the co-operation between the University of L'Aquila and the "Science and Technology Park of Abruzzo". These studies have demonstrated how the use of superconducting materials [5] has allowed to obtain significant levitation thrusts compatible with the high speed mass transportation systems. Therefore, the opportunity to use superconductors for magnetic levitation in "urban light rail" has been investigated.

3 2 The LRM System The LRM system requires a dedicated way and it is suitable to operate on main lines for public transportation in average size cities or feeder lines in large urban areas. The system used is a short vehicle mounted primary and long track secondary. The main components of system are: a) The train, that consists ofmodular vehicles (Fig. I). Each vehicle has two bogies with "electromagnetic runners" and HTSC windings fed by three phase voltage: these allow to obtain simultaneity the levitation, the thrust and the guide of vehicle. b) The guideway (Fig. 2) consists of HTSC stripes, cooled with liquid nitrogen, distributed on bottom and lateral sides of track. module ' bogie Fig. l - Scheme of LRM convoy Levitation and traction Guide and traction 4 Fig. 2 - Section of vehicle and guideway The height of vehicle (air-gap) from ground is about 5 cm. The train can run jn both direction and consists of several wagons (vehicles), each one with a capacity of about 65 passengers.

4 660 Urban Tramport and the Ei~~~~,nrzrnatlr it? rha 21st Canrurv The main data of the wagon are: length (Lv) of 10 m, width (Sv) of 2.60 m, height (Hv) of 2.4Om, tons tare and 16 tons full weight. Each wagon is "self-sufficient" since it has 2 bogies with all the necessary equipment for the traction and levitation. The single bogie has two parallel electromagnetic "runners", consisting of an inductor (primary) with high temperature superconducting wires fed by a threephase voltage. These "runners" used for both levitation and thrust and consists of a core with slots and teeth and a distributed three-phase winding with superconductor wires (Fig. 3). The train rides on a "U" shaped guideway that has 4 HT passive superconducting stripes (Fig. 2) cooled with liquid nitrogen: 1) two are arranged on the bottom of track interacting with the runners, in order to guarantee the levitation and contribute to the traction; 2) two are arranged along the lateral sides for the guide of train and the remanent contribution to the traction. The sheets represent the secondary that interact with the related electromagnetic runners arranged in the bogies of the vehicles. 1 TOP VlEW l J1, - CI \ S.z & C " Superconductor wires FRONT VlEW Fig. 3 - Scheme of the electromagnetic runner 3 The FE analysis of electromagnetic runner Several 3-D Finite Element analyses have been carried out in order to design and analyze the electromagnetic runner: in Tab. l are presented the main data. As mentioned before, the guideway has an "U" shape (Fig. 2) whose dimensions are: 3.10n1 width (SW) and 1.20 m height (Hw). It has, for the overall length, 4

5 Urbarr Tran~pnr-r and the Envir-otzmar~r irz [he 21~1 Canfury 66 1 stripes (0.60m width and 0.05 m thickness), arranged on the bottom and 2 sheets (0, width and 0,01 m thickness) on the sides of track. Table 1 - Main data of electromagnetic "runner" Geometric data Number of pole 4 Number of slots 36 Length (L) 2,63 m W~dth (W) 0,40 m He~ght (H) 0,08 m Pole pltch 0,63 m Slot width 30 mm Tooth wtdth 40 mm Tooth he~ght 30 mm Yoke he~ght 50 mm Air-gap 50 mm Number of conductors per slot 45 We~ght 0,656 t Mam performance at standstill operat~on Voltage 1000 V Frequency 25 Hz Phase current 75 1 A Phase resrstance 3,09 mr Power factor 0,0161 Act~ve power 38,6 kw I,ev~tat~on thrust 48 ItN The bogie (2.90 m length, 2.60 m width and 0.90 m height) has 4 "runners": 2 for the levitation and thrust and 2 for the guide and traction of vehicle. The operation of the "runner" needs an inverter on the board that allows to vary the frequency, during the starting and rated operation. Several numerical tests have been carried out, for a phase voltage of 1000 V, 25 Hz, and air-gap of 0.05 m: the synchronous speed is 31.5 ds: for the superconductor, a resistivity of le-10 Rm has been assumed. Thanks to the 3D Finite Element model, the edge effects have been taken into account. Fig. 4 shows the flux lines distribution in the runner with reference to one pole, while Fig. 5 presents the flux density in the secondary. Moreover, the behaviox of air-gap flux density has been evaluated and the trend is shown in Fig. 6: this trend is due to the presence of slots in the priniary core. Further results are shown in the following figures and concern the single runner perfomnnce. In Fig. 7 are shown the tlvust and levitation forces vs. slip characteristics. The runner allows to obtain levitation forces for all the slip values and particularly during the starting operation and at synchronous speed, while the

6 662 Urban Tramport and the Ei~~~~,nrzrnatlr it? rha 21st Canrurv traction is low; for this reason the traction is given also by a three-phase winding arranged on the sides of guide-way (Fig. 2). Primary, Air-gap 1 \ Secondary: Superconducting plate Fig. 4 - Flux lines distribution (one pole) Fig. 5 - Flux density distribution in the secondary L 4- I --A o o 5 I Llnear abscissa Iml Fig. 6 - Flux density in the air-gap

7 The phase current (Fig. 8) varies from 751 A at starting operation to 715 at synchronous speed. In figures 9,10,11 and 12 are shown respectively the trends of apparent power, active power, output power (related to the traction), the Joule losses and the current density in the secondary of the "runner" l Tract/on I 0 l I Sllp l \' p Fig. 7 - Traction and levitation forces Fig. 8 - Phase current 80 Actlve power Fig. 9 - Apparent power Output power Slip - -- Fig Active power and output power (related to the traction) l 0.8 0, slip Fig Joule losses I L l Shp O8 O Fig Current density in the secondary

8 664 Urban Tramport and the Ei~~~~,nr~rnatzr it? rha 21st Canrurv The slotted primary, arranged over the windings, allows to close the flux lines (Fig. 4) and realize the electromagnetic shielding of passengers compartment. At 0.6 m, that is at minimum distance between the electromagnetic runner and bottom of compartment, the flux density values are very low and this allows to avoid any problem related to the interaction between electromagnetic field and passengers. The inversion runner translating field, allows to brake the train. The use of superconducting materials allow to reduce drastically the windings losses. Respect to the traditional "light rail" systems, the proposed solution allows to annul the detrimental stress, for the urban applications, thanks to the absence of contact between wheels and rail surface; moreover it significantly reduces the acoustic noise. 4. Conclusion The proposed LRM system presents the following advantages, respect to the traditional system with wheels: - drastic reduction of the vibration transmitted by the vehicle on the extend environment; - noise reduction inside and outside the vehicle; - reduction of the vehicle tare and elimination of rotating masses; - dynamic stability by the control of frequency. Some technical problems should be investigated and solved, and these concern mainly the high costs of the HT superconducting materials, and the phase advancer that requires the use of power factor cosrection capacitors. References Vollenwyder K., Linear motor propulsion for urban transit, (7'" International Conference on Magnetically Levitated System and Linear Drives (MAGLEV) - September 2002; Lousanne, Switzerland. D'Ovidio G., Villani M., Crisi F., Monaco S., Navarra A., Lanzara G., Experimental analysis of interaction between circular inductor "way" and inclined sheet-type secondary, 8Ih International Conference on Computer Aided Design, Manujizcture and Operation in the Railway and Other Advanced Mass Transit Systems (COMPRAIL), June 2002, Lernnos, Greece. Lanzara G., D'Ovidio G., Villani M., Crisi F., Navarra A., Testing of experimental equipment with circular inductor "way" and inclined multisheets type secondary, Automotive & Transportation Technology Congress (ATT), July 2002, Paris, France.

9 [4] D'Ovidio G., Crisi F., Navarra A., Villani M., Lanzara G., LIM: optimization of secondary width respect to the tl~rust, 17'" International Conference on Magnetically Levitated Systems and Linear Drives (MAGLEV), September 2002, Lausanne, Switzerland. (51 Lanzara G., D' Ovidio G., Masciovecchio C., Villani M., Superconducting Sheets for Train Support and Traction: Finite Element Analysis, 2"" International Synzposium on Linear Drives for Industry Applications, (LDIA), April 1998, Tokyo, Japan.

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