IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 24, NO. 3, JUNE 2014
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Conceptual Design of Superconducting Linear Synchronous Motor for 600-km/h Wheel-Type Railway Chang Young Lee, Member, IEEE, Jin Ho Lee, Jung Min Jo, Chan Bae Park, Won Hee Ryu, Yoon Do Chung, Young Jin Hwang, Tae Kuk Ko, Member, IEEE, Se-Young Oh, and Ju Lee, Senior Member, IEEE
Abstract—This study introduces 600-km/h wheel-type railway concept propelled by linear synchronous motor (LSM) and deals with the conceptual design for LSM system. The LSM is designed to be of a coreless type, which uses high-Tc superconducting electromagnet (SC-EM) as on-board field magnet. From tentative train parameters, we suggest a conceptual LSM model and its design parameters to achieve the train performances. As high-Tc SC material, we use currently available YBCO tape in designing the SC coil. We produce three SC coil models and estimate tentative design values of each model. The feasibility study described herein provides informative design ranges of LSM for 600-km wheel-type railway. Index Terms—High speed railway, linear synchronous motor, propulsion system, superconducting electromagnet.
I. I NTRODUCTION
T
HE DEMAND for high-speed rail transportations has constantly increased worldwide. Conventional high-speed railways, such as TGV, ICE, Shinkansen, and etc. are being commercially operated at the maximum speed of 300 km/h. And further development programs to increase the travelling speed to 350 km/h or more are ongoing. However, the speed over 500 km/h has been a great challenge in the conventional propulsion system using on-board traction motors and catenary system [1], [2]. Meanwhile, the Maglev, which levitates the vehicle by magnetic force and propels it with linear synchronous motor (LSM), has already accomplished the maximum speed up to 581 km/h in the Japanese Maglev, MLX [3]. From the achievement of MLX, the Maglev has been considered as the potential superspeed railway system over 500 km/h. However, although the Maglev is advantageous in the travelling speed, the vehicle cannot be interoperated with the existing wheel-on-rail track. This interoperability problem of Maglev has been regarded Manuscript received July 16, 2013; accepted September 20, 2013. Date of publication October 4, 2013; date of current version December 13, 2013. This work was supported by the Korean Ministry of Knowledge Economy under Grant PK13005B. C. Y. Lee, J. H. Lee, J. M. Jo, C. B. Park, and W. H. Ryu are with the Korea Railroad Research Institute, Uiwang 437-757, Korea (e-mail:
[email protected]). Y. D. Chung is with the Department of Electrical Engineering, Suwon Science College, Hwaseong 445-742, Korea. Y. J. Hwang and T. K. Ko are with the Department of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea. S.-Y. Oh and J. Lee are with the Department of Electrical Engineering, Hanyang University, Seoul 133-791, Korea. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TASC.2013.2284662
Fig. 1. Concept of high-speed railway with dual-mode propulsion system.
as one of the reasons why it is rarely selected in high-speed railway market [4]. In fact, LSM used in the Maglev is a very attractive propulsion system, which also provides substantial merits in designing the high-speed railway of wheel-type. First, the vehicle does not need heavy on-board traction motor system including inverter and transformer, because the traction power of vehicle is supplied from ground coils on guideway. This makes it possible to design the vehicle much lighter. Secondly, the overhead catenary system, which might cause mechanical contact problems as the speed goes up, is not necessary. Lastly, the slip between wheels and rail does not occur when the vehicle is accelerated and decelerated, because the wheels just play a role of the support and guidance of vehicle. Authors have studied on the new high-speed railway operated with a dual-mode propulsion system of the LSM and the conventional traction motors. This paper introduces the railway concept and the design feasibility for LSM. II. C ONCEPT OF H IGH -S PEED R AILWAY W ITH D UAL -M ODE P ROPULSION S YSTEM Fig. 1 shows the conceptual view of the high-speed railway operated by dual-mode propulsion system. Basically, the vehicle is of a wheel-on-rail type, which has traction motors on wheel-bogies. On both sides of each vehicle, field electromagnets for LSM are installed. The ground LSM coils are installed on the exclusive high speed line. On the existing rail track, the vehicle uses the traction motors to propel it, whereas, on the high-speed line, it is propelled by LSM. As the on-board traction motor system, we consider electric multiple units (EMUs) used in the metro lines. EMU is onecontrol and four-motor system of which traction power per
1051-8223 © 2013 IEEE
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IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 24, NO. 3, JUNE 2014
TABLE I T RAIN PARAMETERS
Fig. 3.
One-side view of LSM model for 600-km/h wheel-type railway.
must exceed aerodynamic drag force at vmax [5]. We used the aerodynamic drag force, Fdrag , expressed as in (2), which was experimentally obtained from the Korean high- speed train model. Where, N means the number of vehicles per train [6] P = F × v = const. Fdrag = 2.4 × v 2 (0.265 × N + 0.25) × 10−3 .
(1) (2)
Fmin was calculated as 144 kN from (2). From Fmin and vmax , the required engine power was given to 26 MW. And, the necessary maximum thrust was given to 275 kN, which can be calculated by the product of the train weight and the maximum starting acceleration. B. LSM Model
Fig. 2. Thrust-speed characteristics curve.
unit is about 840 kW. This is approximately 10 times less than the unit commonly used in the 300 km/h high-speed railways. Therefore, the weight and space of the motor system can be minimized, whereas the maximum speed on the wheel-on-rail track is limited to 80 ∼ 100 km/h. III. C ONCEPTUAL D ESIGN OF LSM A. Train Parameters Train parameters are given in Table I. Route length and demanded mean travelling time were assumed to be 400 km and 40 min., respectively, which are tentative route parameters between Seoul and Busan in Korea. Thus, mean operational speed of train to travel the route was set as 600 km/h, and the maximum speed of train was designed to be 650 km/h. Net weight of vehicle, 304 kN, which is about 30% lighter than conventional one, can be made possible by using one-axle bogie system and fiber-glass reinforced plastic as body material. The maximum starting acceleration was assumed to be 1.35 m/s2 , which is the same as that of high-speed Maglev. Required engine power was determined from the thrustspeed characteristics curve shown in Fig. 2. In general, train is controlled with two modes: constant thrust mode and constant power mode. For the constant power mode, the thrust-speed curve is of a hyperbolic shape drawn as in (1), and the trajectory is maintained over a speed range from the base speed, vb , to the maximum speed, vmax . And the minimum thrust, Fmin ,
Fig. 3 shows one-side view of LSM model for 600 km/h wheel-type railway. Train is designed with double-sidewall LSM excitation system. DC electromagnets and armature winding coils are installed on vehicle and both sides of ground guideway, respectively. There are two types of LSM in designing the armature winding coils and the electromagnet: ferromagneticcored type and air-cored type. We selected air-cored type for the following reason. In ferromagnetic-cored LSM, the normal force interacted between the armature winding coils and the electromagnet is only attraction force. The attraction force dramatically increases as the gap between them decreases. This force is uncontrollable, so that if the attraction forces unevenly act on both sides of the train, the train may lose its balance and be derailed. Therefore, the ferromagnetic-cored type is not suitable to the doublesidewall LSM excitation system. Meanwhile, air-cored LSM produces not only attraction force but also repulsion force, which can be adjusted by the magnetic field angle between the armature coils and electromagnet. Thus, the repulsion forces exerted from both sides of guideway is able to prevent potential derailment of the train at high-speed operation. Instead, the air-cored LSM needs superconducting electromagnet (SC-EM) in order to generate sufficient magneto-motive force (MMF) [7]. Typical thrust and normal force generated by changing the magnetic field angle, δ., are shown in Fig. 4, which is expressed as the following equations. Abbreviations are described in Table II Fthrust = Fmax sin δ (3) (4) Fattraction = −Fmax cos δ √ Li − π g Fmax = 4μ0 ma p 2Na Ia kw1 Nf If kwf e τ . (5) τ
LEE et al.: CONCEPTUAL DESIGN OF SUPERCONDUCTING LINEAR SYNCHRONOUS MOTOR FOR 600-km/h WHEEL-TYPE RAILWAY
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Fig. 4. Typical thrust and normal force as functions of the magnetic field angle between armature winding coil and electromagnet. TABLE II D ESCRIPTION OF A BBREVIATIONS
Fig. 5. Maximum thrust per SC-EM resulting from the increase in MMF of armature coils. TABLE IV S PECIFICATION OF YBCO TAPE P RESENTED BY AMSC C O .
TABLE III D ESIGN VALUES OF LSM M ODEL
In order to determine informative design ranges of the gap and armature coils, we simulated the maximum thrust per electromagnet resulting from the increase of MMF of armature coils. Fig. 5 shows the result. Since there are no saturation parts, the consequent thrust is linearly increased as the increase in MMF. For the given gap conditions from 100 mm to 300 mm, MMF of armature coils required to achieve 20 kN are determined in the range from about 9 kAt to 13 kAt. This range can be reasonably provided as a trade-off between the number of coil turns and the operating current of armature coils. IV. D ESIGN F EASIBILITY OF H IGH -Tc SC C OIL
Design values of the LSM model are summarized in Table III. The SC-EM consists of four SC coils, of which polarity is alternatively excited to reduce the field in the passenger compartment. The total numbers of SC-EM were tentatively selected as 14, considering the length of vehicle in the train parameters. Thus, the required maximum thrust per electromagnet to produce the train thrust of 275 kN was given to 20 kN. As seen in (5), thrust of LSM is determined not only by geometric arrangement of two coils but also by the MMF of each coil. In this feasibility study, we fixed dimensions of two coils as the values given in Table III. The pole pitch and length of field coil were arbitrarily determined in the range which is allowed by the recent technology involved in manufacturing SC coil. Consequently, the pole pitch and length of armature coil determined from those of the field coil. The MMF of SC-EM was assumed to be 700 kAt, which is consistent with the performance of low-temperature SC-EM used in the Japanese MLX [8].
Low-Tc SC-EM manufactured by NbTi wire has been successfully implemented in the MLX. But, since the recent progresses of the 2G high-Tc superconductor, YBCO, would potentially lower the cost of SC-EM, we consider YBCO tape as the winding material of SC coil for the SC-EM. As the feasibility study for high-Tc SC coil when it is designed with YBCO tape, we produced three SC coil models and estimated tentative design values to achieve the performance in MMF. The specification of YBCO tape used in the coil models is of the AMSC’s Amperium tape which is currently available in the market. The specification is listed in Table IV. The coil models are of a racetrack-shape, which was assumed to be fabricated by stacking single racetrack coil shown in Fig. 6(a). The winding numbers of the single racetrack coil was assumed to be 800 in maximum. Length of the coil is all the same as the given dimension in the LSM model. Width and thickness of coil model were approximately calculated with the dimension of the tape and the additional insulation layer of 20% in thickness.
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IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 24, NO. 3, JUNE 2014
Fig. 8. Ic(B, T)/Ic(77K, 0 T) − B characteristic curves of the YBCO tape (presented by AMSC Co.) and SC coil models.
margin against Ic , the cooling temperature will be determined in the lower range than the values suggested in the Table. Fig. 6. SC coil models for SC-EM. (a) Single coil model. (b) Model 1. (c) Model 2. (d) Model 3. TABLE V D ESCRIPTIONS OF SC C OIL M ODELS
V. C ONCLUSION We produced a conceptual LSM model as the propulsion system from the train parameters of 600 km/h wheel-type railway. The LSM model suggested herein is not optimal and does not cover all design parameters. But it provides tentative design ranges and values as a feasibility study to generate the speed and thrust of the train. And three different SC coil models make it possible for us to estimate the operational conditions when they are designed with the YBCO tape available in the market. Based on the results suggested herein, more detailed analysis and design for optimal LSM and SC coil will be carried out as our further researches. R EFERENCES
Fig. 7. model.
Simulation of the maximum perpendicular magnetic field of coil
Table V describes the design values of each coil model. Excitation currents, Iop , are given to produce the MMF of 700 kAt required on the winding numbers of coils. The cooling temperatures of coils were estimated in the ranges where the critical currents of coil, Ic , are higher than Iop . Here, Ic at the cooling temperatures could be estimated from Ic (T, B)/Ic (77 K, 0 T) − B curves shown in Fig. 8 [9]. In the figure, we used Ic − B curve of YBCO tape presented by AMSC Co. [10]. And, Ic − B lines of coil model were obtained by simulating the maximum perpendicular magnetic field experienced in the coil as seen in Fig. 7. If we consider the operating current
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