Electromagnetic Rail Research Articles

Durability and Stiffness Estimation for the Composite Overwrap Electromagnetic Rail Launcher Barrel

One of the ways to decrease electromagnetic rail launcher (EMRL) barrel mass is to utilize composite material overwrap. Design of novel light, stiff, and durable EMRLs requires accurate computational prediction of barrel strength. This paper presents numerical model and corresponding computer code for the calculation of stresses in composite overwrap EMRL barrel. The computer code named, NDSPDE, based on the finite-element method for stresses analysis in complex geometric shapes designs in a plane strain. The code allows carrying out numerical structural studies of EMRL barrels under various electromechanical loads accounting for the orthotropic properties of utilized constructive materials. Depending on the requirements for EMRL barrel stiffness and durability the results of numerical studies allow to select suitable construction materials to optimize both the barrel design and the barrel electromechanical loading conditions. The safety margin evaluation of the side insulators and the overwrap was carried out by classical criterion of maximum tensile stress. Note that in durability assessing of other launcher elements the above safety margin is not applicable, since the stress is not unixial in the most loaded parts of those elements. In case of nonuniaxial stress, evaluation of the launcher structural elements durability requires utilization of more complex criteria, which account for the type of the stress state arising in the launcher elements. This paper presents the numerical results of the EMRL barrel cross-sectional parameter estimation including the glass fiber overwrap, rails, and insulators. Estimations were carried out both for stresses and for durability of the EMRL barrel structural elements.

Real-Time System-on-Chip Emulation of Electrothermal Models for Power Electronic Devices via Hammerstein Configuration

Real-time emulation of device-level power electronics plays an essential role in many industrial applications for design and hardware-in-the-loop testing of system components and controllers. Due to the complexity and heavy computational burden of the real-time hardware implementation of the analytical and the numerical models, this paper proposes dynamic electrothermal behavioral models for diode, thyristor, and insulated-gate bipolar transistor based on the Hammerstein configuration. The power electronic device model parameters are extracted from the known device datasheets and implemented in Zynq System-on-Chip platform with accelerated processing for real-time application. An electromagnetic rail gun system has been employed as the study case to compare the performance of the proposed electrothermal behavioral models with that of off-line simulation models on SaberRD software.

Force Characteristics Analysis for Linear Machine with DC Field Excitations

In urban regions and particularly in developing countries such as Malaysia with its ever-growing transport sector, there is the need for energy efficient systems. In urban railway systems there is a requirement of frequent braking and start/stop motion, and energy is lost during these processes. To improve the issues of the conventional braking systems, particularly in Japan, they have introduced linear induction motor techniques. The drawbacks of this method, however, is the use of permanent magnets, which not only increase the weight of the entire system but also increases magnetic cogging. Hence an alternative is required which uses the same principles as Magnetic-Levitation but using a magnet-less system. Therefore, the objective of this research is to propose an electromagnetic rail brake system and to analyze the effect of replacing permanent magnets with a magnet-less braking systems to produce a significant amount of brake thrust as compared with the permanent magnet system. The modeling and performance analysis of the model is done using Finite Element Analysis (FEA). The mechanical aspects of the model are designed on Solidworks and then imported to JMAG Software to proceed with the electro-magnetic analysis of the model. There are 3 models developed: Base Model (steel), Permanent Magnet (PM) Model and DC Coil Model. The performance of the proposed 2D models developed is evaluated in terms of average force produced and motor constant square density. By comparing the values for the 3 models for the same case of 9A current supplied for a 0.1mm/s moving velocity, the base model, permanent magnet model and DC coil model produced an average force of 7.78 N, 7.55 N, and 8.34 N respectively, however, with increase in DC current supplied to the DC coil model, the average force produced is increased to 13.32 N. Thus, the advantage of the DC coil (magnet-less) model, is, that the force produced can be controlled by varying the number of turns in the coil (N) or the current supply to the coil (I) given by the which is the simple principles of a solenoid: Force(mmf)=NI.

Analysis of current characteristics of the electromagnetic rail gun based on HHT

In this paper, using the B‐dot probe at the end of the gun, the B‐dot's voltage waveform is measured when the armature is being launched. During the launch process, the magnetic field around the probe changes. According to the change of the magnetic field, the probe generates an induced voltage. The Hilbert spectrum of voltage signal is obtained by the Hilbert–Huang transform (HHT). Based on the Hilbert spectrum, the rail states of the launch system are compared. The results show that the waveforms obtained from the B‐dot probes at the rail‐gun breech can be used to analyze the whole process of the launch based on HHT. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A New Finite-Element Method to Deal With Motion Problem of Electromagnetic Rail Launcher

In dynamic launching processing of the electromagnetic rail launcher (ERL), the armature is sliding along the rail while the pulse current flows through the interface between the armature and rails. The distribution of physical fields at the interface of the rail and the armature is quite complex, and meanwhile they may be phenomena like abrasion, melt, erosion, and cutting, which are typical problems of rapid electrical contact sliding. For numerical analysis of ERL considering the movement of armature at the velocity of v, a new method has been introduced in this paper, which has used $v\cdot A = 0$ as a gauge condition by tree technique in Whitney elements. By this method, the interface condition of E has been satisfied while the continuity of the electric scalar potential $\varphi $ and the magnetic vector A across the interface of two conductor region has also been ensured. Finally, the 2-D and 3-D finite-element model has been built by the edge element method. The results of the model have been analyzed and compared with EMAP3D code’s, which have verified the described methods.

Simulation of a Seven-Phase Air-Core Pulsed Alternator Driving the Electromagnetic Rail Gun

As the most efficient and compact sources in pulsed power supply for electromagnetic launchers, the air-core pulsed alternator can supply a current as high as 1 MA with a voltage reached several kilovolts. The machine performs various functions, such as kinetic energy storage, electromechanical energy conversion, and power conditioning, making the electromagnetic launch system compact and lightweight. But due to the short history of the machine and the absence of fabrication experience in China, the air-core pulsed alternator is still in an exploratory stage, and there are lots of key technologies and problems needed to be researched deeply. Taking technical risks and manufacturing costs into consideration, a seven-phase air-core pulsed alternator has been proposed and the machine is under development. In this paper, operation principles of the electromagnetic launch system are presented in detail. The mathematical models of the seven-phase alternator and the rail gun are introduced. Based on the mathematical models, a simulation model about the electromagnetic launchers is built, and it is useful to help us figure out the operation characteristic when the self-excitation machine drives the electromagnetic rail gun with a 200-g projectile. As a result, it is convincing by simulation to prove the drive current can be as high as 1 MA and the projectile is with a velocity of 2 km/s at the exit. Simultaneously, violent transient situations will be illustrated in this text, such as the electromagnetic torque and the rotor speed. Meanwhile, simulation results can verify the analytical method and present the current and voltage straightforwardly. They also have great significance on choosing the proper high power switching devices.

Investigation of the Driving Ability on Concave Armature

Driving ability of the armature is one of the important launching characteristics on rail gun. To push heavier load effectively with less mass is an important goal to pursue for the armature design. The armature used to be launched or push load is mainly designed in C shape. Whether the C-shaped armature is the best choice for the electromagnetic rail gun launching or not? Based on the above question, this paper proposes a novel concave armature. Similar to the principle of arch bridge, the concave shape is used to design the armature arm in order to withstand the electromagnetic force. The concave arm structure can transfer the electromagnetic force to the force that pushes the load and the pressure that the armature applies to rails, so that the concave arm avoids fracture due to the large electromagnetic force, and the driving ability for the armature is improved. This paper focuses on the comparison of driving ability between the concave armature and C-shaped armature. The C-shaped armature and concave armature, with the same mass and similar structure, also with the same load mass, are designed. Electromagnetic and mechanical coupled calculation under the same condition is conducted. Through analyzing the stress and deformation, a primary conclusion is drawn that the concave armature can push a heavy load and has small deformation. An experimental research is carried out to verify the driving ability of pushing heavy load for two armatures. It provides valuable reference for engineering design.

An Electromagnetic Rail Launcher by Quadrupole Magnetic Field for Heavy Intelligent Projectiles

This paper presents a new rail launcher based on a rupole magnetic field. This novel propulsion concept is adopted for launching heavy intelligent projectile. The interaction between the magnetic field and the armature current results in the generation of a large thrust. The thrust acts on the armature where the intelligent projectile is loaded without magnetic shielding, and pushes it forward. The configuration of the rails is given in this paper. Numerical analysis and the finite-element model are adopted to validate the properties of the magnetic field in the launch tube. The current and magnetic field distribution in the armature are simulated in ANSYS Maxwell 3-D and based on which the armature’s structure is designed. The thrusts as function of the rail distance and current are presented. The results show that the proposed rail launcher can project sensitive devices because of its magnetic field features and it can provide abundant thrust for heavy projectile, as well as good stability in launch process.

Analysis of Rail Erosion Damage During Electromagnetic Launch

In the process of launching the electromagnetic rail guns (EMRGs), the erosion damage to the rail surface is mainly caused by the joule heat generated by the rail body resistance and armature-rail contact resistance as the current runs through the rail. According to the joule heat and the law of conservation of energy, this paper develops a formula to calculate the temperature rise of rail surface, proposes the method of using temperature rise of rail surface for representing rail erosion damage, and the mathematical formula indicates the relevance between the temperature rise of rail surface and current, linear current density, armature moving speed, rail material, state of armature-rail contact, and skin effect. Dynamic test data required for calculation of rail current, muzzle voltage, armature bore displacement, and velocity are obtained through launching tests, and are used to calculate the surface temperature rise of rails of different materials during the launch of EMRGs. The calculation produces the temperature rise of rails at any positions along the length direction. The results are compared with the photographs of rail surface after the launch, and the analysis verifies the feasibility of representing rail erosion damage with temperature rise of rail surface.

Research on Insulation Problems Under Multishot Experiments in Electromagnetic Rail Launcher

Insulators between conductive rails assume a leading role in electrical insulation and support fixation. Failure of insulating materials during continuous repetitive launches has been found in experiments, the performance changes of insulators will directly affect efficiency and lifetime in repetitive electromagnetic launcher system. Many factors may influence the insulating performance because of complicated working condition, such as strong pulse stress and high temperature. A multishot minor-caliber launcher was designed for the study of the insulating performance. The length of the launcher is 890 mm with a caliber size of 10 mm × 10 mm. C-shaped aluminum alloy armatures and glass-reinforced polymer insulator G10 are used. The muzzle speed is above 2 km/s. After the multishot experiments, the surface topography and surface resistivity of the insulators were measured by megger and digital microscope. The experimental and testing results show that the surface resistivity of G10 reduces gradually with the increase of experiment times, also the surface resistivity of different locations changes. Some pits and cracks appear at individual locations on the G10 surface, the phenomena of resin wear and fiber exposed are observed. Metal deposition is also found on the insulator surface by different types at different positions. Surface flashover voltage is measured after ablation.

3-D FEM Analysis on Electromagnetic Characteristics of an Air-Core Pulsed Alternator

In pulsed power supply for electromagnetic launchers, air-core pulsed alternators have obvious advantages to enhance the power and energy densities with a compact and lightweight structure, and it is gradually to be the prime candidate for pulsed power supply. Compared with conventional machines, an air-core pulsed alternator will supply large amounts of energy over millisecond time with a huge current as high as 1 MA and a high voltage reached several kilovolts. Since the short history of the air-core pulsed alternator in China, the related theoretical research is not enough and the fabrication experience is absent. At present, research has shown that the performance of the air-core machine cannot be evaluated by the 2-D method due to the nonexistence of ferromagnetic materials, and it is very necessary to carry out the 3-D analysis by a finite-element method (FEM). This paper will present a 3-D model of the machine according to the accurate geometric size, and the model is used to develop electromagnetic analysis by the FEM and a transient simulation about the no-load EMF is carried out too. In order to understand the mechanism and process of electromechanical energy conversion, it is obviously important to figure out the magnetic field distribution in the machine. Meanwhile, in order to evaluate the strength of the windings, the calculation of electromagnetic forces and torques is developed when the machine drives the electromagnetic rail gun with a current of 1 MA.

The Dynamic Performance and Thermal Computation of Electromagnetic Rail Launcher Considering Parameters Variation

For the electromagnetic rail launcher, the parameters variation has obvious effect on the dynamic performance and efficiency. This paper constructs the system simulation model of the electromagnetic rail launcher by using of Simulink software, and then analyzes the influences on the system dynamic performance for main devices. Based on the parameters and large current condition, the launching efficiency model is constructed, and the energy distribution characteristics are obtained. The loss of rail, armature, and feeder equipment is 38.7%, and the loss of arc extinguishing equipment is about 4.76%, so the heat loss is about 43.46% of total loss. When considering that the other loss is 33.37%, the system energy efficiency is 23.17%. Based on the design of the small prototype, the energy loss characteristics of the full prototype in launch rail and its temperature features are discussed in detail. The peak temperature is 276 °C after 11 continuous shots with converting coefficient being 5000 W/( $\text{m}^{{{2}}}\cdot \text {K}$ ), and it can decrease 58 °C if the better convection boundary condition is achieved, which means the rail can meet the requirement of the thermal management.

Metastability of Pulse Power Loads Using the Hamiltonian Surface Shaping Method

Pulse loads on an electric ship are becoming more prevalent as ship component technologies move to more electric power. However, these pulse loads, such as electromagnetic aircraft launch systems, rail guns, lasers, and radar all can have a destabilizing effect on the ships power distribution network. Typically these types of loads are modeled as constant power and are analyzed for stability with small-signal models and techniques. However, small-signal methods are insufficient for pulse power load stability. This paper will present a brief overview of small-signal methods. Then a large signal metastable analysis method based on a Hamiltonian surface shaping and power flow control methodology based on the average-mode model of dc–dc converters will be presented. The results show that the nonlinear time-variant load pulses create nonlinear limit cycles and dynamics. The stability of the limit cycles can be assessed through a comparison of the power generated versus power dissipated in the system. Simulation, hardware-in-the-loop, and hardware experimental results will be presented.

Design of a Superconducting Self-Supplied Electromagnetic Launcher Proof of Concept Using HTS REBCO Conductor

A superconducting magnetic energy storage (SMES) is an attractive power supply for electromagnetic rail launchers (EMRL), which require pulse currents to launch projectiles at very high speeds. Moreover, the accelerating force in an EMRL may be enhanced by adding a background field, a principle known as launcher S3EL concept (Superconducting Self-Supplied Electromagnetic Launcher) consists in using the SMES both as a power supply and for background field generation. The challenge is to reach the operating current and peak magnetic field of such launchers, which can be up to hundreds of kA and up to 10 T. The use of a high-temperature superconductor is mandatory to maintain superconducting operation during a launch, though operation at 4.2 K is foreseen to benefit from the RareEarth-BaCuO (REBCO) tape high critical current densities. The aim of this work is to derive a practical design for a 1-m-long small-scale S3EL proof of concept using REBCO coated conductor, with a reduced output velocity (100 m/s). After preliminary sizing studies, the spatial constraints for the SMES-Launcher integration is presented. A parametric joint analytical and Finite Element Method (FEM) study is conducted to refine the design and maximize the operation margins while maintaining the launch performances. Finally, cable design and discharge method suitable to reach the required operating current are presented.

The Numerical Analysis Methods of Electromagnetic Rail Launcher With Motion

To solve the sliding electrical contact problems, it is necessary to take into account the interface conditions of magnetic field intensity $H$ and magnetic flux density $B$ and also those of electric field strength $E$ and current density $J$ when the armature is in contact with the rail. As the interface condition of $E$ is not implicitly included in the simplified weak forms of governing equations, the discontinuous electric scalar potential $\varphi $ is used in the nodal element, the continuous $\varphi $ in the edge elements, and meanwhile ${v}\cdot A = 0$ serves as a gauge condition by tree technique to deal with the interface condition of $E$ . The penalty method is adopted to set up the coupling equations for the interface conditions and the boundary conditions of current inlet surface. The use of the above methods leads to the establishment of the finite-element equations for the motion in the conditions of the nodal and edge elements and to the construction of the corresponding numerical model. The comparison of the result obtained from the model with the result of calculating the eddy current of the 2-D or 3-D electromagnetic rail launchers proves the proposed methods to be feasible and effective.

Passage of the discharge current through the plasma–electrode interface in the electromagnetic rail accelerator channel

We investigate the phenomena that accompany the acceleration of a free plasma piston (without a striker) in the electromagnetic rail accelerator channel filled with different gases (argon, helium). An intense glow appears in the shock-compressed layer (SCL) in the case of strong shock waves that produce a high electron concentration (~1017–1018 cm–3) behind the front. We have proposed that explosive electron emission (EEE) ensures the high-intensity emission of electrons, the passage of a part of the discharge current through the SCL, and the glow of the SCL. The velocity of a shock wave for which the strong electric field in the Debye layer at the cathode causes EEE from its surface and the passage of the current in the SCL has been determined. It has been concluded that, for high velocities of the plasma, the EEE is a universal mechanism that ensure the passage of a strong current through the interface between the cold electrode and the plasma.

Electromagnetic-Mechanical Characteristics Study of a High-Speed Electromagnetic Launcher

The high-speed electromagnetic (EM) rail launcher has a wide range of applications. An inductive shunt device is usually paralleled with the rails of the launcher as an approach to limit the muzzle arc by transferring the extremely high armature current. The shunt parameters will significantly influence the rail current, armature velocity, and device stress conditions, which also makes the physical process more complicated. In this paper, a circuit-EM-mechanical coupled simulation model is developed to analyze the launching process. Based on this model, the influences of shunt impedance, armature resistance, and capacitor energy are investigated numerically. The EM force, stress conditions, and deformation of the shunt are studied as well. In addition, some launcher design suggestions are given according to the conclusion.

Numerical modeling of electromagnetic railgun rail temperature field

Electromagnetic railgun temperature field characteristics are important basis for rail design and thermal management. This paper carries out numerical modeling of electromagnetic railgun rail temperature field and studies the temperature field characteristics during and after launch of armature. Firstly, the thermodynamics environment of rails during and after armature launch is analyzed; Then, on the basis of rail conducting contact heat model and rail 3D finite element model we have built, the rail temperature field is simulated by finite element software ANSYS. The temperature field of rail at each moment is obtained. The research results show that: The maximal temperature rise of rail is near the armature initial position; the rail temperature rise gradually decreases from the armature initial position to the muzzle; under the condition of parameters setting in this paper, the temperature rise of each shot near the armature initial position is approximately 8.945°C.

Electromagnetic Tomography Rail Defect Inspection

With the train’s speed improving, and running interval time decreasing, traditional rail defect inspection methods cannot meet the efficiency requirement of railway industrial standards. In this paper, we propose a new online rail defect inspection method which is using electromagnetic tomography (EMT) technique. The method uses the tomographic approach to measure the alternating magnetic signal modulated by cracks in the rail and then reconstruct the distribution of cracks. The difference to common eddy-current rail defect inspection is, that the EMT can acquire the defect shape and position information. The sensor and signal processing hardware of the EMT rail defect inspection system can be installed on the common passenger or freight train. This solution allows continuous inspection, and therefore reduces the critical accident events caused by rail defect. A model is designed and the forward problem of the model is calculated using electromagnetic finite-element method. Rail defect reconstruction simulations are done using linear backprojection and Tikhonov regularization algorithm to verify the principle of this method. Furthermore, an experimental system is built to simulate the rail defect. The laboratory experiment results show that the electromagnetic rail defect inspection is a feasible approach for reconstruction of the shape and position information of rail defect.

Multirail electromagnetic launcher powered from a pulsed magnetohydrodynamic generator

The operation of an electromagnetic multirail launcher of solids powered from a pulsed magnetohydrodynamic (MHD) generator is studied. The plasma flow in the channel of the pulsed MHD generator and the possibility of launching solids in a rapid-fire mode of launcher operation are considered. It is shown that this mode of launcher operation can be implemented by matching the plasma flow dynamics in the channel of the pulsed MHD generator and the launching conditions. It is also shown that powerful pulsed MHD generators can be used as a source of electrical energy for rapid-fire electromagnetic rail launchers operating in a burst mode.