Performance calculation for single-sided linear induction motors with a double-layer reaction rail under constant current excitation

A method for computing the performance of a single-sided linear induction motor (SLIM) with a double-layer reaction rail, under constant current excitation, is presented. This method takes into account the reaction of secondary eddy currents on the airgap field, transverse edge and longitudinal end effects, together with skin effect, saturation, nonlinear magnetic permeability, and hysteresis in the solid steel core of a reaction rail. In an equivalent circuit of the machine, the mutual and secondary impedances are found from a solution of the two-dimensional electromagnetic field distribution. Modifying factors account for configurations in which the width of the secondary conductive layer is different from that of the steel core, and in which the thickness of the conductive overhand is different from that over the steel core. Good correlation is obtained between analysis and test results from a large-scale linear induction motor (LIM) at Queen's University. The developed expressions are appropriate for small and large LIM's and may also be used for constant voltage excitation conditions.     

Transient modeling of multiparallel tubular linear induction motors

In this paper, we model single and multiparallel generator driven tubular linear induction motors by the current filament method, in transient and dynamic states. Using a previously written code for transient and dynamic modeling of a single motor, we simulate a sample motor noted in a reference paper and compare the results with those obtained by using our current filament method. This comparison confirms the accuracy of our method. Finally, we model a system of two or more parallel motors and show that it is feasible to achieve greater muzzle velocities by paralleling certain designs of motors.     

A hybrid method of analysis of low-speed linear induction motors

A current-excited low-speed solid-iron secondary single-sided linear induction motor (SLIM) with aluminum reaction rail is considered, A hybrid method of analysis consisting of field analysis in conjunction with the multilayer transfer-matrix concept with adjustment of secondary iron permeability to match the tangential magnetizing field in each layer is developed. It is shown that this method gives valuable information on permeability and flux penetration in secondary iron. Computed thrusts are in good agreement with test results.     

Experiments on the lateral stabilisation and levitation of linear induction motors

Conventional linear motors always have a component of force which acts at right-angles to the normal (levitation) and longitudinal (traction) forces, and which attempts to expel the secondary side-ways from under the primary. This paper describes some different types of machine in which these lateral forces always act inwards, i.e. attempt to align the primary with the secondary. The first machines described rely upon an application of either the shaded-pole principle, or the reluctance principle, to produce a lateral stability which is conditional on the relative widths of the primary and secondary. A later development was the double-skewed or 'herringbone' motor, in which inwards-travelling fields are set up by appropriate skewing of the primary slots. This machine is shown to be somewhat disappointing, in that stability was once again restricted to very narrow secondaries. Transverse-flux geometry has led to the introduction of a large number of devices which are much simpler in construction than their longitudinal-flux counterparts, but which will stably levitate, guide, and propel a sheet secondary. Difficulty is encountered in maintaining stability when iron is introduced into the secondary iron circuits, but the paper shows how stability can be restored by using a double U-core construction.     

Vertical unstable stability of electrodynamic suspension of high-speed ground transport

The problem considered is the vertical oscillation of a superconducting solenoid moving over a conducting sheet in connection with the electrodynamic suspension of high-speed ground transport. The oscillation is considered to be unstable at a sufficiently high speed. The current oscillation in the superconducting solenoid caused by its mechanical oscillation is also investigated. The superconducting properties of a solenoid are found to have a pronounced effect on stability. Both the theory and numerical results are presented. Methods of oscillation damping are also discussed.     

Analysis of tubular linear induction motors, using the concept of surface impedance

By using the surface-impedance method, equivalent circuit for an axial-flux tubular induction motor is obtained. This circuit is used to determine the performance characteristics of a laboratory model. The calculated results are compared with experimental results. The voltages and currents in the equivalent circuit are related directly to the field quantities within the actual device.     

Catalytic motors for transport of colloidal cargo

Autonomous micro- and nanomotors should, in principle, deliver materials in a site-directed fashion, powering the assembly of dynamic, nonequilibrium superstructures. Here we demonstrate that catalytic Pt-Au nanomotors can transport a prototypical cargo: polystyrene microspheres. In addition, motors with Ni segments can overcome both Brownian orientational fluctuations and biased rotation of the rod-sphere doublet to enable persistent steerable uniaxial motion in an external magnetic field. Assuming a cargo-independent motive force, the speeds are inversely proportional to the Stokes resistance, which we compute using a completed double-layer boundary integral equation. In addition, we demonstrate motors transporting cargo via chemotaxis toward a H2O2 fuel source.     

Modelling of squirrel-cage induction motors for electromagnetic transient programs

The authors discuss the modelling of the squirrel-cage induction motor. The experimental measurements on motors of different rated power, 1-90 kW, clearly show that the single-cage model does not fit the torque-speed curve adequately. Consequently, when the speed varies in a wide range, only the double-cage model can fit the curve well with the squirrel-cage induction motor. The equivalence between the two most commonly used double-cage models in the literature is studied, and a method to find the equivalent parameters is developed. In addition, the induction motor modelling in the PSCAD/EMTDC and EMTP-RV simulation programs is examined, and the inaccuracies resulting from the use of manufacturer data are discussed.     

感应电机矢量控制系统仿真研究

针对基于空间矢量脉宽调制技术（SVPWM）和转子磁场定向控制原理的感应电机矢量控制系统,利用控制功能模块化的设计思想,在Matlab／Simulink中建立功能独立的子模块如矢量控制模块、速度控制模块、坐标变换模块、SVPWM子模块等,并将这些功能模块拼装组合,构建了电流、转速双闭环感应电机矢量控制仿真模型。仿真结果表明基于模块化设计的感应电机矢量控制仿真模型是有效可行的,为电机控制器的设计提供了一种途径。     

Robust adaptive numerical compensation for friction and forceripple in permanent-magnet linear motors

This paper describes a robust adaptive compensation method for friction and force ripple present in the dynamics of permanent-magnet linear motors. The method is used in ultraprecise positioning applications. The compensation algorithm consists of a PID component and an adaptive component for estimating friction and force ripple. The adaptive component is continuously refined on the basis of just prevailing input and output signals. Computer simulations and real-time experimental results verify the effectiveness of the proposed scheme for high-precision motion trajectory tracking     

Canadian developments in superconducting Maglev and linear synchronous motors

Canadian developments in the application of superconducting magnets for levitation, synchronous propulsion, and guidance of high speed inter-city ground transport are described. At 480 km h^?1 a 100 passenger vehicle weighing 300 kN is levitated 15 cm clear of a flat guideway (minimizing ice and snow accumulation) by eight 3.85 × 10⁵ ampere-turns 100 × 30 cm magnets interacting with eddy currents induced in two 80 × 1 cm aluminium strips. The variable speed LSM uses fifty 5 × 10⁵ ampere-turns 40 × 150 cm magnets interacting with split three-phase windings energized in 5 km sections and phase angle controlled to give 72% efficiency and 0.82 power factor. A lateral restoring force of 10⁴ N cm^?1 is produced by the propulsion magnets interacting with the levitation strip edges and with flat null-flux loops overlying the LSM windings. A review of cryogenic systems indicates that isochoric dewar operation is best suited for Maglev vehicles. The test facility, using stationary full-scale superconducting magnets and guideway components mounted on a 100 km h^?1 vertical axis 7.6 m diameter wheel, is now fully operational and LSM tests are being performed.     

Field analysis of the magnetic systems for tubular linear reluctance motors

We report a study of tubular linear reluctance motors (TLRMs) in various types of magnetic circuits. We carried out magnetic field analyses and calculated integral parameters of the field. We also determined static characteristics and electromagnetic parameters of the motor. We found good agreement between our calculations and tests of the motor with sinusoidal excitation.     

A novel, single-mode piezoceramic plate actuator for ultrasonic linear motors

A new type of piezoelectric plate actuator for ultrasonic linear motors has been developed. These new piezoelectric actuators use the principle of asymmetric resonant excitation of the piezoceramic plate in a special resonant mode consisting of a standing two-dimensional extensional wave in a piezoceramic plate. The behavior of the actuator has been simulated with finite-element method (FEM) software and the simulation results checked with single-point contact measurements on the surface of the actuator. This paper describes this work and closes by describing the new ultrasonic translation stages based on this design.     

Harnessing biological motors to engineer systems for nanoscale transport and assembly

Living systems use biological nanomotors to build life's essential molecules--such as DNA and proteins--as well as to transport cargo inside cells with both spatial and temporal precision. Each motor is highly specialized and carries out a distinct function within the cell. Some have even evolved sophisticated mechanisms to ensure quality control during nanomanufacturing processes, whether to correct errors in biosynthesis or to detect and permit the repair of damaged transport highways. In general, these nanomotors consume chemical energy in order to undergo a series of shape changes that let them interact sequentially with other molecules. Here we review some of the many tasks that biomotors perform and analyse their underlying design principles from an engineering perspective. We also discuss experiments and strategies to integrate biomotors into synthetic environments for applications such as sensing, transport and assembly.     

Calculation and effects of end-ring impedance in cage induction motors

This paper describes a method for calculating the end-ring impedance of a squirrel-cage induction motor using the method of images. The method is verified by using finite-element analysis. A second method is also discussed, although it was found to be too simple to be accurate. The second part of the paper addresses the effect of this impedance variation on the motor performance with particular attention to the starting torque.     

High-order terminal sliding mode control for induction motors based on current decoupling

为提高感应电机转速控制系统的性能,提出了速度环、电流环的高阶非奇异终端滑模控制方案.该方案通过设计非奇异终端滑模面来提高系统的响应速度和控制精度;通过设计高阶滑模控制律以直接获得平滑的控制信号,有效削弱常规滑模的抖振现象;对速度环,考虑了系统负载转矩和转动惯量的变化,所设计的高阶滑模控制律使系统具有良好的鲁棒性;对电流环,利用电压补偿实现交、直轴电流完全解耦,提高电流控制器的动态性能.仿真结果表明,该方案有效地消除了常规滑模存在的抖振现象,并且跟踪精度高,对负载扰动及转动惯量变化具有较强的鲁棒性.     

轨道随机不平顺影响下高速铁路地基动力分析模型

考虑轨道随机不平顺影响,建立了移动车辆-有砟轨道-路基-层状地基垂向耦合振动解析模型。模型中,将虚拟激励法和解析的波数-频率域法有效结合起来,直接由轨道不平顺的功率谱密度得到准确的动态轮轨力功率谱。将移动列车轴荷载和轨道随机不平顺引起的动态轮轨力考虑为傅里叶级数表示的谐波叠加形式,根据线性系统叠加原理,求得地基动力响应功率谱估计值与时程结果。利用在波数域内直接计算位移频谱、划分合适谐波区间等技术,显著提高了随机振动响应功率谱和时程的计算效率。对比分析了地基表面测点垂向振动加速度时程与频谱的理论计算与现场实测结果,证明了本文模型的合理性。