Study on the improvement of the power efficiency of MAGLEV

Kyoung Bok Lee 1†, Ji Young Lim *, Doh Young Park2, Won Seok Choi3, Hyun il Kang3

1 Daejeon Metropolitan Express Transit Corporation, Daejeon 300-738, Republic of Korea 2 Korea Institute of Machinery & Materials, Daejeon 305-343, Republic of Korea

3 Department of Electrical Engineering, Hanbat National University, Daejeon 305-719, Republic of Korea

*corresponding author: hiking@hanbat.ac.kr

Abstract. Urban maglev train is regarded as an environment friendly next generation transportation system which is accord with green city construction. Incheon airport demonstration route is preparing an operating by commercialization business second in the world. Maglev train has an excellent gradeability and a curve driving ability more than existing steel wheel because it is driving floating by force of electromagnetic without wheels, but it is difficult to predict substantive operating cost without accurate data about power consumption in levitating. In this paper, we present an energy utilization methods to minimize the maglev energy consumption by analysis of electric power comparison of between maglev system and steel wheel.(Daejeon metro line 1)

Keywords: Urban maglev system, light rail, steel wheel, electric power utilization, power consumption

1 Introduction

Recently, the environmental problem of the earth has becoming more serious and the development of eco-friendly transportation is expected to solve this problem. Maglev train by means of green transportation, it has been mentioned as an alternative to relieve traffic congestion in the city by less noise pollution. Maglev train is a method of propulsion that uses magnetic levitation to propel vehicles with magnets to overcome adhesion force between wheel and rail. Without dust, eco friendly train propelled by linear motor produce less noise and vibration than conventional trains and it provides a good ride comfort for passengers. Also, maglev train has excellent gradeability and major safety advantages than other trains. There is no possibility of derailment or overturn because of driving a vehicle with a structure that surrounds the rail.

At present, Linimo is considered the world's first commercial automated urban maglev system. Domestically, urban maglev pilot line in incheon international airport envisioned as one of the government-funded R&D projects is about to open in 2013. Our country is expected to be one of the three possessed maglev commercialized line

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in the world with Japan and China [1].

2 Power Consumption Analysis

2.1 Power consumption analysis test

To calculate for compare of power consumption of steel wheel and maglev, each vehicle test was performed. The steel wheel train of Daejeon metro line1 and maglev train of Korea Institute of Machinery & Materials (KIMM) were used in the test vehicle. Main system performances are as Table1. Power consumption measurement test was progressing in Daejeon Metro and KIMM test line as Fig.1. Two test lines length is same as 1.3 km, but considering the curve and grade, the test was conducted straight section of test line to achieve similar condition.

Table 1. Test vehicle features (steel wheel and maglev train)

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(a) Daejeon Metro test site (b) KIMM test site

Fig. 1. Test site for power consumption measurement

Fig. 2. Train speed profile

Train operating pattern applied speed profile of Fig.2 equally. The maximum speed is 50km/h and moving distance of each manual notch are as P3-B6(279m), P3-B5(316m) and P2-B6(402m).

2.2 Power consumption measurement and analysis

2.2.1 Power measurement of each Notch

Fig.3 shows a voltage-current waveform of maglev train and steel wheel train at empty vehicle and conditions of each notch are as P3-B6(propulsion 75%-braking power 85%), P3-B5(propulsion 75%- braking power 72%) and P2-B6(propulsion 50%- braking power 85%). Horizontal axis is in time related function and sampling rate of measuring instrument is 2ms.

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Fig. 3 Voltage-current wave form

2.2.2 Analysis of current pattern

As appears by inverter current pattern of Fig.3, it shows typical inverter current pattern. When steel wheel train is propelled, maximum current 700A is consumed and then regenerative brake by regenerative receptivity of trolley wire totally is faded out around vehicle speed 4~5km/h and is stopped by pneumatic brake. On the other hand, maglev train uses regenerative (electric command) brake and plug brake as seen in Fig.4 and regenerative brake is converted into plug brake around the 20km/h speed. Furthermore, adjusting slip frequency, extinction time can be changed.

Fig. 4 Motor current & speed of Maglev

2.2.3 Power consumption analysis of car On the basis of measuring results, power consumptions of each notch analyzed in table 4. In comparison with steel wheel train, power consumption of maglev train is average 116% higher than.

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3 Conclusions

In this study, it was confirmed that power consumption of maglev train is average 116% higher than steel wheel train. As a result of analysis, low regenerative brake characteristics and energy loss by levitating gap appeared main causes of increasing of power consumption. In the case of LIM of maglev train, efficiency of maglev train falls because regenerative braking is performed until 20km/h and then plug braking is performed until 5km/h about shortage of braking [2]. New technology, using purely regenerative brake until train stop, was recently developed [3]. If these techniques applied to maglev train, energy efficiency and braking characteristics would be improved. Moreover, by installing energy storage system (ESS) in substation, energy efficiency can be improved through the maximum use of regenerative energy by increasing of trolley wire acceptability. Another way to improve of LIM efficiency is to design small gap. However, if the gap of LIM set up too small, it will be difficult to control levitating due to strong attraction power of magnetic flux. So it is important to setting optimization air-gap. If the technologies for efficiency improvement of LIM applied to future maglev train, it will be contribute to improve of the energy efficiency and the brake system.

Table 4. Power consumption analysis

References

1. B.C. Shin, W.J Kim, D.Y Park, J.G. Baek, et al. (2011) Introduction of urban maglev

program, Journal of railway , 14(2), pp. 26-32. 2. S.C. Park, W.M. Lee, J.C. Kim, Y.H. Park (2008) Regenerative Braking Characteristics of

Linear induction Motor for MAGLEV, Spring 3. conference of Korean society for railway, Daegu, pp.1866-1870. 4. H.M. Lee, G.D. Kim, S.C. Oh, C.M. Lee, et al. (2006) A study on application of pure

electric braking system for urban transit system, CICS, Daejeon, pp.263-265.

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