Vol 4, No 3 (2018)

Common cylindrical bearingless drives require a separate thrust bearing, which is fed by a DC supply. Here, a technique is presented, which enables the feeding of the thrust bearing by an artificially generated zero-sequence current between the two star points of the two parallel windings in the bearingless PM synchronous machine. This way, no additional DC supply for an axial active magnetic bearing is needed. It is replaced by two three-phase inverters as stator winding supply, which are needed in any case to generate torque and lateral rotor force in the motor. This examination explains the technique of adapting the electric potential of the star points in two three-phase windings of the motor. The focus is on the determination of the operating area (maximum zero-sequence current and band width). It is constrained by the bearingless motor due to torque and lateral force ripple as well as additional eddy current losses. On the other hand, the DC link voltage and the modulation degree of the inverter for simultaneous motor operation as well as the bearing inductance limit the system dynamic. It is shown that the proposed technique is applicable for a modulation degree < 0.866, taking into account that other constraints by the bearingless machine and the inverter are mainly noncritical.

Since the high-speed maglev line in Shanghai was put into operation in 2003, it has been running safely for 15 years, maintaining the highest speed of public ground traffic 430 km/h and 99.8~99.9% punctuality. Since 2001, China ministry of science and technology (MOST) has been supporting the research and development of high speed maglev transportation technology. In 2016, under the support of the MOST, China Railway Rolling stock Corporation (CRRC) started to lead the program of engineering research of Maglev. The aim of the program is to develop 600 km/h high speed Maglev system and 200 km/h medium speed maglev system. The newly developed high speed Maglev system could be tested, verified and applied on the planned Shanghai - Hangzhou high speed Maglev line.      

Since the operation opening of Changsha Maglev Airport Express Line in May 2016, Hunan province has planned to build more maglev line with top speed 100–160 km/h. Following the operation of urban maglev in Changsha and Beijing, the Qingyuan Maglev line in Guangdong province  began to build at the end of 2017. The new maglev line will connect hot spring tourist attractions and Changlong theme park (animal park) in 2019.                               

This paper introduces the application and construction of maglev transportation in China, recent R&D status, further plans and trend of development.

In the late 1990s thyssenkrupp Transrapid GmbH successfully qualified the Maglev Vehicle TR08 and obtained the type approval certificate. Based on that design, in 2001-2003 three five-car vehicles for the first commercial high speed Maglev Line in Shanghai have been manufactured and set into operation. The VIP-Run took place over 15 years ago and the commercial operation has been running for almost 15 years at great availability.

The Transrapid system concept of small autonomous redundant electronics based modules facilitates significantly smooth maintenance - diagnosis, testing and system inspection.

Thanks to intelligent diagnostics, the use of easily interchangeable plug-in units, the dimensioning of the spare parts inventory according to the expected failure rates and the replenishment lead time, the maintenance efforts are still within the forecast range at the beginning of the project. Furthermore, the maintenance concept is essentially unchanged since the beginning.

There are no special materials that are subject to a potential shortage or price leap, but all according to normal industrial base.

Thanks to the low level of stress to components on board, most electrical and electronic units are still on-board as original equipment, which are 15 years old and at no end of life is visible.

But in case of repair or replacement, the challenge is the adaptation to the volatile market of electronic components. This includes the necessary lead-time for adaptive development and qualification, which has to be considered.

On the side of the vehicle supplier, a small smart team of electronics experts is managing obsolescence and compensates discontinuation.

The paper tells how it works and appreciates trustful cooperation of the supplier in Europe with the operator in China.

Aim: To show that the trestle of arch type allows to realize various limiters of movements of the levitating vehicles.

Methods: Patent search, comparison with analogs, system approach.

Results: Options of designs of trestles for freight and passenger traffic are offered.

Conclusion: In all cases it is necessary to look for a compromise between achievement of the goal of functioning of maglev-system and costs of its construction and service.

This paper presents a novel vector control method for three-degree-of-freedom resonant actuator in order to improve its controllability. The effectiveness of the presented method is verified through electromagnetic field analysis using 3-D finite element method:

Issue: A three-degree-of-freedom resonant actuator has a great potential to broaden the application range of linear oscillatory actuators because it has a lot of advantages: high efficiency, simple structure, etc. However, this actuator has low controllability because the magnetic structure of each axis is not independent.

Aim: To establish a novel vector control technique suitable for our actuator.

Materials and methods of the studies: Electromagnetic analysis employing 3-D finite element method.

Results: In this study, the novel vector control theory was constructed on the basis of four-phase system. The new dq model was achieved by considering 3-D coordinate transformation. The proposed method is able to decrease the influence of thrust interference from other axis and achieved higher controllability.

Conclusion: The results of the study will contribute to a practical use of the three-DOF resonant actuator.

Background: As high-speed rail and other transportation technologies are moving forward and gaining funding in the United States, the push for MagLev is not receiving the necessary support that would make it a viable alternative in the near future. Major changes in the approach to implementing MagLev could make a better case for it, specifically for carrying freight. One alternative that has been considered in the past is the modification of existing freight railways to support MagLev. For this to be economically feasible and practical, such a solution has to be able to support both conventional freight trains and MagLev freight.   

Aim: The successful application of Partially Magnetically-Levitated Freight (PMLF) technology achieved by integrating superconducting MagLev technology with current railroad design and operations.

Methods: A MagLev freight system that is envisioned to use existing rail routes must be designed to be compatible with the existing railway infrastructure. To accomplish this, every component utilized by the railroads must be examined in detail to determine if and how it could be affected by the proposed PMLF. In addition, components that will need to be modified for PMLF operation must undergo a retrofit design and testing process. The design scope must also include an examination of all existing tasks and activities that are being performed by the railroads such as track maintenance and repair. Any procedures that affect or are affected by the addition of PMLF will need to be modified. Finally, superconducting MagLev technology must be optimized and advanced for application to PMLF.   

Opinions and Discussions: The dual use of railway lines has substantial cost advantages when compared to building new dedicated MagLev freight corridors. In fact it could make the entire proposition very appealing if proven to be technically feasible. However, there are certain limitations and concerns that would cause policy makers to reject such a proposal unless such obstacles can be shown to be temporary and non-critical. Essential rail installations such as switches are presently difficult to modify in a way that would ensure reliable functionality for both MagLev and conventional freight trains, and grade crossings pose safety risks. It is difficult to envision the tremendous leap forward of merging MagLev with existing freight rail lines when much more basic technologies such as positive train control are not even fully implemented. Consequently, it is a challenge to advance MagLev in the United States where new dedicated freight corridors are considered to be cost-prohibitive and dual use railway lines pose uncertainties that railroad companies simply do not want to solve. However, there is one more solution has not been considered that would allow a MagLev freight train to navigate on existing railway infrastructure without disrupting traditional rail utilization. This solution is a partially magnetically-levitated freight train.

Results: After reviewing the fundamental components, systems and operations of the railways in the United States, it will be feasible and practical to introduce magnetic levitation technology to assist in moving freight on existing rail routes. PMLF trains will be able to take advantage of magnetic levitation on sections where the track has been upgraded to allow its use and much higher speed while still being able to travel on unmodified sections with the same speed as traditional trains.

Conclusion: Modifying existing freight rail with magnetic “quasi-lift” technology is a much lower cost alternative to building an entirely new MagLev infrastructure. This alternative will provide very important benefits including enhancing safety in the rail industry. In its first phase of implementation, the proposed PMLF system will levitate a significant portion of the weight of the train but still utilize the existing steel rails for traction and guidance. The most evident advantages of this approach include reduced wear on rail and other supporting elements, and a significant reduction in friction and energy use. Locomotives, freight cars and all other components could be made lighter and travel speeds will increase dramatically due to less impact and other effects. Later phases of implementation will focus on magnetic traction and guidance. The acceptance and success of this partially levitated system will eventually lead to fully levitated freight transport technology. Sometimes it is necessary to take smaller steps to achieve the desired future.

Background: The no-stationary regimes of the magnetically levitated train’s (MLT) motion were the object of research.

Aim: The purpose of the study is to evaluate its dynamic qualities and loading in such regimes.

Methods: The work was carried out by conducting a series of experiments with a computer model of train’s dynamics.

Results: The simulation results reflect its motion in the modes of acceleration, passage of the tunnel, as well as service and emergency braking.

Conclusion: An analysis of these results made it possible to evaluate the dynamic properties of a train in various non-stationary motion modes and its loading in their process.