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The electromagnetic suspension system (EMSS) plays a critical role in providing attractive force for middle-low-speed maglev trains, which contains two critical components– an electromagnet and a steel track. However, with the acceleration of trains, the eddy current generated by the relative motion between the electromagnet and the track becomes intensified, which may directly weaken the attractive force. To maintain the suspension airgap between the iron yoke and the track stable, more current needs to be inserted into the winding of the electromagnet. The local thermal surge existing in the winding may appear due to the overloaded input current for long term, which may cause the insulation aging or even damage of the winding. If the short circuit accident occurs between the neighboring turns of the winding due to the inter-turn insulating damage of the winding, the loss of suspension force tends to be deteriorated undoubtedly. In this paper, a novel hybrid suspension system mixed electromagnetic and permanent magnetic modes is proposed for enhancing suspension force with economical power consumption. But, when applying permanent magnets for assisting electromagnets, the firm absorption (FA) phenomenon needs to be considered. Two suspension schemes with unequal-width and unequal-height iron yokes are launched for reducing FA risk. The corresponding FEM models have been built and verified by experimental results. The comparison of different suspension schemes under dynamic condition with different relative velocity between the suspension module and the track has been undertaken in the end.

The integrated grounding system for high-speed trains consists of two parts: on-board dynamic and fixed terrestrial grounding sub-systems. The on-board grounding sub-system contains working and protective grounding modes, both of which share the rails as the common path for discharging current. Current reflux occurs frequently, which can contribute to the circumflux in the ‘train body – grounding wheel set – rail’ circle, due to the dynamic coupling effects between grounding points. The path and value of the circumflux vary transiently because of the changing impedance between the grounding wheels and rail under the dynamic conditions. In our previous work, a 2D grounding model was built to evaluate the impact from the current reflux, but the lateral and vertical impedances of train bodies and rails were ignored. In practice – when the protective and working grounding is applied independently to rails on the left- and right-hand side separately – the current reflux can be restricted by benefitting from the impedance existing in train bodies and rails. It therefore becomes essential to build a 3D ‘train–rail’ coupling grounding model accounting for the full-dimension impedances, while different grounding distribution protocols is considered to improve the grounding performance.

The ‘train-rail’ integrated grounding system for high-speed trains plays the critical role in providing the unique path for power feedback, which mainly consists of two parts - the on-board dynamic grounding sub-system and the fixed terrestrial grounding sub-system. The on-board dynamic grounding sub-system can be classified into two types of grounding modes – working grounding provides the discharging path for transferring the traction power; while the protective grounding maintains reference ground potential for the train body – both of which share the rail as the common path for discharging current. Thus, the traction current discharged from the working grounding wheel sets flows through the neighboring protective grounding wheel sets back to the train body, forming as the ‘train-rail’ current reflux. The ‘train-rail’ current reflux may result in the appearance of a ‘train body’ (TB) current, which may rise the potential of the train body. The TB current and voltage may cause electromagnetic interference to the on-board equipment, electrochemical corrosion on grounding wheel bearing or even on-board partial temperature surging. In this paper, a ‘train-rail’ coupling integrated grounding model is launched to evaluate both the TB current and voltage. Based on this model, different grounding distribution schemes have been tried and compared, considering the impact brought from TB current and voltage. The external grounding resistors are installed in series at the protective grounding wheel sets implemented, with the aim of restricting the TB current and voltage. Ultimately, the best-performed grounding scheme of installing external resistors is found out.

As a unique exit point for power supply systems of high-speed trains, the onboard grounding system plays a critical role in providing the path for returning the traction current to traction substations. The grounding system applies two grounding modes: the working grounding and the protective grounding, both of which share the power discharging channel, the steel rail. Current reflux normally appears between the working grounding point and the protective grounding point due to the wheel-rail coupling effect. The “train–rail” current reflux may result in the appearance of a “train body” (TB) current, which may cause the onboard partial temperature surging. Moreover, some operational conditions, such as raising pantographs or operating vacuum circuit breakers, may trigger TB overvoltage, which may threaten the safety of the onboard devices. In this article, a “rail–train” coupling grounding model is built to evaluate both the TB current and overvoltage based on the measured parameters. The particle swarm optimization (PSO) algorithm is adopted to optimize this model with the aim to achieve a satisfactory balance between the TB current and overvoltage. The main difficulties of this multivariable multiobjective task include that many grounding parameters are involved meanwhile restricting both TB current and overvoltage. Ultimately, optimal solutions are achieved, considering design demand.

High speed trains receive traction electrical energy from a high-voltage catenary via a pantograph catenary system (PCS). As the velocity of trains increases, the traditional PCSs face significant challenges, such as strong aero resistance under high-speed conditions, severe electrochemical corrosion caused by poor contact between the pantograph strip and the catenary, harmful wear both on the pantograph strip and the contact wire produced by high-speed sliding friction between them, etc. The effectiveness and reliability of the PCS has a direct impact on the performance and safety of the HTS power supply. In order to alleviate some of these bottleneck effects related to the operation of the currently used PCSs, especially under high-speed conditions, this paper proposes a novel configuration where rotatable pantograph rollers replace the currently used pantograph strips. As the sliding friction is now replaced by rotating friction, this has numerous benefits, such as less friction heat, better heat dispersion and improved catenary-tracking performance. Moreover, should the whole system be modularized, it could adapt to different levels of traction power through adjusting the number of rollers.

Purpose In high-speed trains, the energy is supplied from a high voltage catenary to the vehicle via a pantograph catenary system (PCS). Carbon pantograph strips must maintain continuous contact with the wire to ensure safety and reliability. The contact is often confined to a particular spot, resulting in excessive wear due to mechanical and thermal damage, exacerbated by the presence of an electric arc and associated electrochemical corrosion. The effectiveness and reliability of the PCS impacts on the performance and safety of HSTs, especially under high-speed conditions. To alleviate some of these adverse effects, this paper aims to propose a configuration where a circular PCS replaces the currently used pantograph strips. Design/methodology/approach Two dynamic multi-physics models of a traditional PCS with a carbon strip and a novel PCS with a circular pantograph strip catenary system are established, and the electrical and mechanical characteristics of these two systems are compared. Moreover, a PCS experimental platform is designed to verify the validity and accuracy of the multi-physics model. Findings A novel circular pantograph system is proposed in this paper to alleviate some of the shortcomings of the traditional PCS. Comparing with a traditional PCS, the circular PCS exhibits superior performance in both electromagnetic and thermal aspects. Originality/value The paper offers a new technical solution to the PCS and develops a dedicated multi-physics model for analysis and performance prediction with the aim to improve the performance of the PCS. The new system offers numerous benefits, such as less friction heat, better heat dispersion and improved catenary-tracking performance.

The tramwave catenary-free system (TCS)—a novel type of electrified transit system for urban railways—receives traction energy from a flexible ground-embedded ferromagnetic strip, which is energized only if a corresponding segment is located underneath the vehicle body. The current collector in the TCS is equipped with an “I-shaped” permanent magnet combination that produces a lifting force on the flexible ferromagnetic strips with octopus-shaped copper sheets located on the surface of the strips underneath the ground. The vehicle’s high-voltage circuit conducts when an electrical contact is maintained by the attractive force of the permanent magnet combination mounted inside the magnetic current collector. However, it has recently been observed that due to the dynamic processes during the electrical contact a severe electrochemical corrosion may occur on the surface of the octopus-shaped copper sheets, which can jeopardize the safe operation of the whole electrified transit system of trams. In order to identify the origins of this electrochemical corrosion, the dynamic characteristics of the TCS have been evaluated with particular attention paid to the impact of eddy currents on the attractive force of the permanent magnet combination under variable operational velocities of vehicles. Based on the dynamic characteristics of TCS, the arc erosion process on the surface of the copper sheet has been reproduced using an arc-discharge experimental platform and the causes of electrochemical corrosion in the TCS have been found. The damage development trends—under increasing speeds of trams—evaluated by the dynamic model of the TCS are consistent with the statistical data for practical damage situations.

The suspension force − a critical factor in the operation of middle-low-speed maglev trains − is provided by electromagnets. However, the eddy current effect produced by the relative motion between electromagnets and the steel track causes a reduction of the suspension force, especially under high speed. A novel type of permanent-electro-magnetic suspension system is proposed to improve performance by considering the variation of material characteristics with temperature. A 3D dynamic finite element model of this hybrid system − accounting for the influence of temperature − has been created to study the variation of magnetic flux distribution, suspension force and guiding force under different operational speeds of the train, in comparison with the electromagnetic version. Verified by simulations, the hybrid system has superior performance offering a powerful suspension force and a reliable guidance force even at high speeds of the train.