Junyong Lu

Research on End Effect of Linear Induction Machine for High-Speed Industrial Transportation

Due to the difference of movement and boundary conditions between long-primary double-sided linear induction motors (DSLIMs) and short-primary DSLIMs, the longitudinal end effect is different. This paper analyzes the dynamic longitudinal end effect of long-primary LIMs according to the basic principle and electromagnetic field theory and explains the difference of magnetic field traveling wave and its influence between these two kinds of DSLIM. The equivalent circuit model and correction factors considering the end effect are described through theory analysis. To verify the validity of the model, 3-D field analysis by Ansoft 3-D is implemented, and the field distribution is presented. The analysis results have a good agreement with the results where the end effect is considered than that where the end effect is not considered. A useful conclusion is that, with proper selection of the secondary poles and proper attention to the slip that the machine is operating at, the end effect will have a much smaller influence than that in the short-primary DSLIM. It provides a good way for this kind of machine design and industrial application in the future.

Research on Two Types of Linear Machines for Covert Airstrip Electromagnetic Catapult

In this paper, two types of feasible linear machines, including linear permanent magnet brushless dc motor (LPMBDCM) and linear induction motor (LIM), have been presented for covert airstrip catapult. First, the electromagnetic launch profile, requirements, and common design principle are introduced. Then, the base configurations and dimensions, including the stator and mover, are analyzed, respectively. Finally, the different performances and equivalent circuit parameters are compared in detail. The results show that the mover of LIM is much longer and higher than that of LPMBDCM, which is a key factor in real application. The difference in power factor and efficiency between LPMBDCM and LIM is also quite significant, which would determine the requirements of the supply current or voltage. At the present state, the LPMBDCM seems to be a better candidate for this project because of higher efficiency and better power factor, which can evidently decrease the capacity of the power supply and facilitate the power inverter design.

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 φ is used in the nodal element, the continuous φ in the edge elements, and meanwhile v · 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.

Investigation of Phase Unbalance Characteristics in the Linear Induction Coil Launcher

The asynchronous induction linear motor (AILM) is the key part in the asynchronous induction coil launcher, and a multisegment primary block feeding AILM is investigated in this paper. The phase unbalance characteristics of a traditional linear motor could be ignored when the poles are six or more; however, due to the existence of long unexcited primary between the entry and exit end of AILM with multisegment primary, the static longitudinal end effect is significantly different compared with a traditional linear motor. Through many experiments, a phenomenon has been found that the AILM had unbalanced mutual inductances, where Lac = Lbc = kLab, and the scale of k is from 1.57 to 6.25, which depends on the length of the unexcited primary. Under balanced terminal voltage conditions, the phase current shows serious unbalance in the prototype machine. It may bring much difficulty to the control system. Based on the unbalanced phenomenon and discipline of mutual inductances, the unbalance mechanism is analyzed by electromagnetic field theory and Ansoft software. The influence of the thrust, yoke field, and parameters because of this kind of unbalance is presented. The experimental results show a good agreement with the theory analysis. It provides a new way for the design and implementation of this kind of machine in the future.

A Multisegmented Long-Stroke Dual-Stator Pulsed Linear Induction Motor for Electromagnetic Catapult

Multisegmented dual-stator pulsed linear induction motor (LIM) is suitable for electromagnetic (EM) catapult based on the former research. This paper mainly analyzes the numerical model of same and reverse mode of the dual stator, magnetic thrust and EM parameters, and the magnetic field distribution has been built by finite-element model and the static performance are gotten by the prototype machine. Based on the analysis results and static experiments, the closed-loop control models for the dual stator have been established, and the dynamic launch test has been performed by using of multisegment prototype LIMs. The test results show that the dual-stator LIMs can accelerate the 300-kg load to the speed of 15 m/s within 11-m launch stroke. The fluctuation of the slip frequency is quite small and the block transition is smooth during the launching process. The test results show good agreement with the commanded values, which verify the dual-stator LIM model and control strategy.

Research on a Linear Permanent Magnet Brushless DC Motor for Electromagnetic Catapult

Linear permanent magnet brushless DC motor (LPMBDCM) is used for electromagnetic catapult, which may offer significant advantages, in terms of efficiency, high speed and accelerations of heavy payloads, capability of high forces and so on. In this paper, a LPMBDCM, which is constructed on transverse flux stator and permanent magnet mover, is investigated. Firstly, the magnetic circuit design is presented, and the rated work performances are analyzed. The rated input voltage, current, thrust and power efficiency is 4000V, 18041A and 1.3896MN, 0.97, respectively. Then, to validate the characteristic of the basic design, the system simulation model including the power supply model and power condition model is built using Simulink, and the launch trajectory is gotten by the model. Finally, a small scale prototype machine and relevant control system based on DSP chip is fabricated on the basis of the results. The experiment results indicate the subscale catapult start successfully and run smoothly. The current curve shows a good agreement with the simulation result of whether Ansoft or Simulink.

Thinking and Study of Electromagnetic Launch Technology

The use of electromagnetic launch (EML) technology in the future launching mode is an inevitable trend. Based on the analysis of the common characters of EML technology, this paper presents the status of three technological branches such as EM aircraft launch, EM rail gun, EM thrust launch, and discusses some concrete problems and related research achievements in detail. Furthermore, clues and important points proposed in this paper will provide valuable reference for developing EML technology.

Performance Analysis of Linear Induction Motor of Electromagnetic Catapult

Based on the operating principle of linear induction motor (LIM), this paper has analyzed the performance of the LIM consisting of a long sectioned transverse flux stator and a short flat aluminum mover, proposed the basic requirements and working modes of this special type of a catapult, described the optimal design methods of the LIM and discussed in detail some important parameters affecting the operating performance, such as the slot width, pole pairs, and the thickness of the mover. Then, the optimal system design and the discussion of performance are carried out based on the T-type equivalent circuit model with the covered and uncovered sections. The phase current, phase voltage, power capacity, and height are 11359 A, 3000 V, 409 MVA, and 1.73 m, respectively. The launch profile is also derived from the model. To verify the electromagnetic compatibility of the LIM, the 3-D magnetic model is established. The results show that the magnetic fields fall to the earths ambient level at 1 m above the stator, which cannot bring low-frequency electromagnetic interference to the environment.

High Rate Pulse Discharge of Lithium Battery in Electromagnetic Launch System

Abstract Aimed at the miniaturization of the power-supply system for electromagnetic launch (EML) system, this paper deals with the problem of high rate pulse discharge of lithium batteries in the EML system. In order to reduce the number of batteries on series-parallel to increase the energy density, the factors such as safety, exotherm and life cycle must be taken into consideration, and there is need for optimization in terms of selection and design as well as discharge control of the battery. According to the power requirements of the EML system, the battery safety and discharge ability are important indexes in the aspect of selection and design, which refer to the design principle for selected batteries and the design scheme for raising their discharge ability under the precondition of discharge, and in the aspect of discharge control, the balancing-discharge control strategy is adopted to reduce the duration of high-rate discharge and the heat generation and extend the service life of batteries according to the EML operating conditions. Finally a test platform is established for verification.

A Compulsator Driven Reluctance Coilgun-Type Electromagnetic Launcher

Reluctance coilgun (RCG) is a special coilgun which uses solid ferromagnetic material instead of induction coil as projectile. RCG has shown great advantages and potential in the application of antiterrorism weaponry due to its simplicity, reliability, and excellent controllability. As a compact lightweight pulsed-power supply (PPS), the compensated pulsed alternator (Compulsator) will play a key role in promoting this kind of electromagnetic weapon into practical applications. Focused on a specific RCG which has conductive rails and brushes, this paper deduced the electromagnetic force analytical formula by using the virtual displacement principle and researched the feasibility of the electromagnetic launch design scheme which uses compulsator as the PPS of the RCG system by co-simulation method. Finally, this paper finished tests of the system by taking advantages of a small demonstrative RCG and a scale-model prototype of the compulsator. The results indicate that the design scheme is completely feasible.