Sensorless control of a linear reciprocating switched-reluctance electric machine

It is proposed to use a simple switched-reluctance electric machine that does not have windings or permanent magnets on a movable part to develop a linear reciprocating electric machine intended for use as an electric generator together with a free-piston internal-combustion engine. It is noted that one of the most difficult problems in the development of such a linear electric machine is the development of a control system. A sensorless control algorithm is considered. Information on the stator-phase inductance of the electric machine and its variation is used to determine the position of the movable part. For its estimation, probing voltage pulses of known duration are applied to the phase. The amplitude of the current pulses caused by them will be proportional to the phase inductance. A mathematical model of electromagnetic processes is used to test the efficiency of the proposed control algorithm and determine appropriate control parameters. Since stator phases have separate magnetic circuits and are not magnetically connected, the electromagnetic processes in each phase are considered independently. Model parameters are determined experimentally using an experimental prototype of the considered electric machine, for which the dependences of the phase flux linkage and the generated force on the phase current for different positions of the movable part are obtained. The results of the investigation of processes in the considered electric machine at different frequencies of the movable part are given. It is found that, at frequencies of the movable part close to the nominal frequency, the phase should be connected to the power supply even before the movable part reaches the extreme position. Control using probing pulses applied to the operating phase is impossible, because the level of these pulses does not reach the maximum value until the phase is switched on. In this case, it is necessary to use the probing pulses of another, nonoperating phase to determine the position of the movable part. Such an algorithm makes it possible to control a linear reciprocating switched-reluctance electric machine at both low and high frequencies of the movable part. The obtained results confirmed the correctness of the adopted approaches to the development of a sensorless control algorithm.     

双定子/双转子永磁同步电机电压矢量确定方法

首先基于直接转矩控制原理提出了双定子/双转子永磁同步电机双转子运行时,内部电机控制电压矢量的确定方法,然后考虑到内部电机特点与Matlab所提供永磁电机模型的差别,建立了电机等效仿真模型.仿真结果证明本文所提出的方法有效.其结果对在混合动力电动汽车中开发双定子/双转子永磁同步电机的直接转矩控制系统具有意义.     

旋转电机第三功能初探

基于传统旋转电机机电能量转换理论,提出了旋转电机第三功能的概念,该旋转电机无传统电机的电能或机械能输出,而是充分利用旋转电势的二次电流损、磁滞涡流损及机械杂散损耗等,将输入的能量全部转化为传统意义上的"损耗",即全部转换为热能.介绍了原理结构、工作机理,进行了基本解析和实验研究.研究表明旋转电机第三功能的可行性,可构成新型旋转电磁热机,除具有传统热机的热效应外,还具有对水媒质的磁化软化功能、防垢除垢功能及良好的节能效果,具有广阔的应用前景.     

A new approach to designing electrical machines on the basis of numerical simulation

An approach that enables one to calculate the electromagnetic field in an electric machine in conjunction with the calculation of currents in windings and the rotation of a rotor under the effect of electromagnetic forces and loads is considered. The capacities of the considered methods for designing electrical machines are demonstrated for a number of examples. The calculated results are compared with the experimental data obtained for an induction electric motor with two short-circuited windings on the rotor.     

永磁电机有限元时步法的研究与应用

对有限元时步法在永磁电机中的应用进行了研究,阐述了基于二维场路耦合时步法的永磁电机模型。采用一台具有特殊转子磁路结构的永磁电机进行了仿真分析,结合试验结果证明了该模型的正确性并指出利用永磁电机的有限元模型结合控制策略是现代电机及其控制系统仿真的方向。     

Nonlinear model and momentary performance capability of a cagerotor induction machine used as an automotive combinedstarter-alternator

This paper presents the calculated and the measured performance capability of a cage rotor induction machine used as a direct connected, crankshaft speed, combined starter-alternator for an automotive diesel engine in an experimental hybrid electric vehicle. The calculated results are based on a nonlinear equivalent circuit model of the machine in which saturation is considered only in the stator and rotor magnetizing flux paths. The development details of this model are given as well as several sets of calculation results for a prototype induction machine. Finally, measured maximum performance results for the test machine are presented and compared with model-based calculated results for the same operating conditions of speed, terminal voltage and current     

Application of Direct-Drive Wheel Motor for Fuel Cell Electric and Hybrid Electric Vehicle Propulsion System

This paper presents a gearless wheel motor drive system specifically designed for fuel cell electric and hybrid electric vehicle propulsion application. The system includes a liquid-cooled axial flux permanent-magnet machine designed to meet the direct-drive requirements. The machine design implements techniques to increase the machine inductance in order to improve machine constant power range and high-speed efficiency. The implemented technique reduces machine spin loss to further improve efficiency. The machine design also optimizes the placement of magnets in the rotor to reduce cogging and ripple torque. An original cooling system arrangement based on the use of high thermal conductivity epoxy joining machine stator and liquid-cooled aluminum casing allows the very effective removal of machine power loss. Design details and experimental results are presented.     

Comparative study of 3-D flux electrical machines with soft magnetic composite cores

This paper compares two types of three-dimensional (3-D) flux electrical machines with soft magnetic composite (SMC) cores, namely, claw-pole and transverse-flux machines. 3-D electromagnetic field analysis is conducted for the computation of some important parameters and optimization of the machine structures. An equivalent electric circuit is derived to calculate the machine performance. The analysis methods are validated by experimental results of a single-phase claw-pole permanent-magnet machine with an SMC core. Useful conclusions are drawn from the evaluation and comparison of two machines with SMC cores.     

Investigation of electromagnetic force components in SRM under single and multiphase excitation

This paper presents the results of an investigation of components of the electromagnetic force in the air gap of an 8/6 switched reluctance machine (SRM). Using a Maxwell stress method, variations of radial and tangential force components due to saliency of the machine and saturation have been studied. Access to distribution of the force components acting on the rotor and stator enables us to provide a more accurate picture of the torque generation and vibration in this family of electric machines. Furthermore, distribution of magnetic forces under multiphase excitation has been studied in detail. Our findings show that bipolar excitation of SRM phases, resulting in a short flux path magnetic circuit, favors its efficiency and power quality while generating higher torque with less pulsation. This is a significant improvement, particularly for automotive applications where the difference in the required number of power electronics components can be justified. An experimental 2-kW 42-V 8/6 SRM drive which has been designed and manufactured in our energy system laboratory was targeted for this study. In addition to our extensive finite-element analysis, experimental results have been provided to prove theoretical claims.     

Performance of coreless-winding axial-flux permanent-magnetgenerator with power output at 400 Hz, 3000 r/min

An axial-flux permanent-magnet machine (AFPM) topology with a coreless winding is proposed for generator units required aboard ships, aircraft or hybrid electric vehicles. In the proposed AFPM configuration, the winding consists of rhomboidal-shaped coils encapsulated in fiber-reinforced epoxy resin. The coils have a double-layer arrangement to leave space for a cooling water duct being used to remove heat directly from the interior surface of the winding. The overall machine structure is compact and lightweight and, due to the lack of an iron core, generator operation with power output at 400 Hz can be accomplished with high efficiency and acceptable voltage regulation. This paper discusses the basic design and construction of AFPM generators with coreless windings and experimental results taken from a 16-pole machine prototype rated 230 Nm, 3000 RPM are also reported     

Experimentally generating faults in rolling element bearings via shaft current

The purpose of this research is to develop a method for experimentally generating in situ bearing faults. To motivate this topic, experimental results are provided that illustrate how the act of removing and replacing test bearings drastically alters the machine vibration and stator current spectral characteristics. Based on this observation, a method is developed that employs an externally applied shaft current to initiate and progress a bearing fault in an accelerated timeframe. This experimental method begins with a new, undamaged bearing and progresses it throughout its entire lifecycle in situ. The test machine is a standard induction motor that can be interfaced with any load and operate at any arbitrary speed or load level throughout the bearing failure process. Data generated by this experimental method can then be used to evaluate the performance of various bearing condition monitoring schemes.     

Compact permanent-magnet generator for hybrid vehicle applications

In hybrid electric vehicle (HEV) drivetrains an electrical generator is coupled onto the shaft of an internal-combustion engine (ICE) in order to process either the entire or a given fraction of the traction power required by the vehicle wheels. As such an ICE-driven generator is being confined within the vehicle hood and is exposed to heating resulting from ICE operation, high compactness, totally enclosed construction, and suitable machine cooling arrangement become challenging targets the generator design must deal with. Due to unique characteristics such as higher torque per volume and higher efficiency compared to other machine topologies, the axial-field permanent-magnet machine topology was selected for a 15-kW-at-4500-r/min-rated generator prototype that would be utilized in a demonstrator of an HEV drive train. This paper describes the original solutions adopted for the design of such an HEV generator and reports experimental results taken from the prototype machine.     

Integrated Starter Generator: The Need for an Optimal Design and Control Approach. Application to a Permanent Magnet Machine

This paper proposes to apply optimal approaches to the design and control of a highly constrained electric machine. The developed approach is applied on a permanent-magnet integrated starter generator (ISG) but may be applied on any high-constrained electric machine. One of the main problems in the use of optimal approaches is the accuracy of the models used by the optimizer. In our approach, we propose to proceed in two steps. 1) Optimal design: the model is purely analytic, and some phenomena are neglected (cross saturation). Under these conditions, the electric machine design is optimal for a limited number of constraints. The design model uses a classic uncoupled d,q reluctant circuit model (with saturation taken into account). 2) Optimal control: once the machine is calculated, the design constraints are validated by a finite-element (FE) method. The FE method allows to use a more accurate model to compute optimal currents for the control on the whole torque-speed plane. In our case, we use FE results to model the cross-saturation phenomenon. The optimizer is common to both cases and is a classic commercial sequential quadratic programming algorithm. This model is validated by experimental results based on an ISG. This paper shows that optimal design and control allows for permanent-magnet machine, high flux-weakening mode, and high-efficiency operations even for a simple machine structure     

交流差频电力测功机的方案研究

本文论述的“交流差频电力测功机”方案是一种节能型电力功机。测功电机定子直接接电网,转子与内燃机同轴连接,差频发生器给转子绕组提供一个电压和频率可调,相序可变的三相交流电源,达到回收内燃机试验能量的目的。     

发电机内部短路分析研究最新进展

回顾了发电机内部短路研究的发展状况,阐述了大型汽轮和水轮发电机内部故障研究 的最新进展和新问题。认为在电机内部故障分析中必须突破理想电机的限制;多回路分析可 以较好地考虑气隙磁场空间谐波的影响,成为分析电机内部故障的有效手段。最后,从实际 应用出发,探讨了内部故障计算的简化方法,强调简化时必须注意物理概念的合理性,并应 得到实验验证。     

On the variation with flux and frequency of the core loss coefficients in electrical machines

A model of core losses, in which the hysteresis coefficients are variable with the frequency and induction (flux density) and the eddy-current and excess loss coefficients are variable only with the induction, is proposed. A procedure for identifying the model coefficients from multifrequency Epstein tests is described, and examples are provided for three typical grades of non-grain-oriented laminated steel suitable for electric motor manufacturing. Over a wide range of frequencies between 20-400 Hz and inductions from 0.05 to 2 T, the new model yielded much lower errors for the specific core losses than conventional models. The applicability of the model for electric machine analysis is also discussed, and examples from an interior permanent-magnet and an induction motor are included.     

A brushless electric motor with a transverse magnetic flux and disk rotor

Brushless permanent magnet machines (BPMMs) have a greater efficiency and smaller overall dimensions than do other types of machines and are widely used in electric drives for various purposes. Two types of BPMMs are used in practice: BPMMs with a classical double-layer-distributed stator winding and BPMMs with a toothed-step stator winding. There exists another type of BPMM with a transverse magnetic flux (transverse flux motors, TFMs) which is being actively studied. In TFM electric motors, the magnetic lines of fluxes of the poles of rotor end perpendicular to the direction of rotor rotation. Stator windings in these machines are fabricated as rings coaxial with rotor, and the magnetic circuit of stator consists of separate fragments. Specialists assert electric TFMs have a higher specific power—the ratio between the output power and the mass of the machine—than the electric motors of other type. They are of interest, first and foremost, for electric drives without reducing gears. In most TFM, only a half of the poles of rotor are magnetically connected with circular phases of stator. In this work, the TFM design with disk rotor is described, in which the magnetic flux of all poles of rotor is coupled to the circular phases of stator. The stator magnetic circuit in this machine consists of P-like elements, and alternation of polarity of these elements is provided due to the change of their position. As a result, the magnetic flux coupled to the circular phase increases doubles, as do the machine torque and power. Some results of modeling of a three-phase electric motor are presented. The results were obtained using the Ansys Maxwell computer code, including a graph of the change of torque on the shaft of a machine under rotation of the rotor under conditions of sinusoidal currents in phases.     

Neural-network-based sensorless maximum wind energy capture with compensated power coefficient

This paper describes a small wind generation system where neural network principles are applied for wind speed estimation and robust control of maximum wind power extraction against potential drift of wind turbine power coefficient curve. The new control system will deliver maximum electric power to a customer with light weight, high efficiency, and high reliability without mechanical sensors. The concept has been developed and analyzed using a turbine directly driven permanent-magnet synchronous generator (PMSG). In addition, the proposed method is applied to a 15-kW variable-speed cage induction machine wind generation (CIWG) system. The simulation studies of a PMSG small wind generation system and experimental results of a CIWG are provided to verify the validity of the method.     

凸极同步电机V形曲线的解析计算

同步电机V形曲线能表明同步电机在大电网上运行时如何合理地调节电机的无功功率输出,是同步电机的重要运行特性曲线。已有文献的理论分析和推导大都限于隐极同步电机,对凸极同步电机V形曲线的理论分析推导较少。对凸极同步电机应用其功角方程和稳定条件,通过求解关于sin2q和sinq的3次方程的方法,分别就凸极同步电机稳定极限、功率因数、功率角的计算进行分析,得到了凸极同步电机V形曲线的解析表达式以及同步电机在cosj为定值时IM关于If的解析公式。利用计算机的高速运算能力可以迅速获得V形曲线。该方法可以推广到隐极同步电机。