高频群脉冲电化学加工电流检测电路设计

主要介绍了高频群脉冲电化学加工的基本原理,重点分析了加工过程中电流检测及短路保护措施及电路设计方案,其次介绍了待检测的电流信号形式及电子功率器件——绝缘栅双极型晶体管（Insulated-Gate Bipolar Transistor,IGBT）.针对应用实例,选择的电流测量方法为电流-磁场转换法的霍尔传感器.阐述了保护电路的设计,并分析了电路的性能,证明能够满足加工需要.     

风门挡板型电-气阀门定位器的智能化设计

本文介绍了一种由4-20mA电流控制的风门档板型电-气阀门定位器的智能化设计。详细叙述了风门档板型定位器原理、硬件电路设计及软件编程。说明了4-20mA电流采集电路设计及计算、风门挡板控制、软件控制算法等。     

基于电流比较器的小直径钻头防折断电路设计

小直径钻头在加工深孔时,常常会出现钻头突然折断的现象。在分析影响钻头折断因素的基础上,根据负载增大,电机电流相应增大的原理,提出基于电流比较器的防折断电路设计。该电路通过电流比较器比较正常钻孔时主轴电机工作电流与实际加工时主轴电机电流的大小。当实际加工电流大于正常工作电流时,输出高电平,高低电平开关电路通电,使得摇臂升降电机反转,将钻头从孔内提升;当实际加工电流等于或小于于正常工作电流时,输出低电平,高低电平开关电路断开,摇臂升降电机正转,钻头钻削孔。     

变频电机轴电流现象分析及对策

分析了变频电机轴电流产生机理及危害,介绍了轴电流的检测分析方法,最后提出了防止变频电机轴电流危害的措施。     

电机控制系统中的电流检测技术

指出了电流检测技术在电机控制系统中的重要性,介绍了常用的几种电流检测手段及其工作原理.针对采样电阻和霍尔电流传感器,详细给出了电流采样信号调理电路原理图.最后提出了元器件选型原则及使用注意事项.     

特殊电流比互感器的检定

介绍了电流比是小数的电流互感器的检定，以及电流比例标准的灵活应用及检测时给被检电流互感器带来的附加误差。     

基于电流模的荧光信号放大器和滤波器的设计

提出了一种采用基于电流模的放大器和滤波器电路设计方法,并利用第二代电流传输器CCⅡ实现了三阶巴特沃思低通电流模滤波器。在对第二代电流传输器结构和原理进行分析的基础上,利用CCⅡ设计了三阶巴特沃思低通电流模滤波器,并把R和C提取到CCⅡ芯片外面使它更好应用于低频荧光信号测量。电路经过Pispice的仿真证明了电路的可行性,从而提高了荧光信号检测电路的速度和信噪比,使得检测精度大大提高。本文提出的方法正确、原理清楚、电路可行。并且,电流模技术为微弱荧光信号的低噪声测量、放大和滤波提供了一条可行的技术路线。     

数控机床主轴电流与切削参数关系研究

简单介绍了监测刀具状态的重要性,阐述了主轴电流与刀具磨损量之间的线性关系,同时提出了主轴电流与切削参数之间存在着必然联系。设计了检测电流信号的测试系统,建立了主轴电流与切削参数关系的数学模型,并通过多元线性回归处理确定了该模型中的未知系数。利用F检验法验证模型呈显性成立。通过相对误差及剩余标准差计算,验证了该模型精确度非常高,满足工程实际需要。最后得出了铣削加工中切削参数对主轴电流影响的显著度由强到弱的顺序。     

高精度程控电流源的设计

采用ADuC812单片机作为整机的控制单元,通过软件和外围电路设计,使程控直流电流源具备实时检测实际输出电流值的功能,并通过采样将实际输出反馈到单片机中,单片机对数据进行分析、处理后再重新调整D/A输出的值,从而达到稳流的目的。所设计的电流源还具有电流可预置、可步进调整以及可同时显示电流预置值和实测值等功能。该系统具有结构简单、工作稳定、纹波电流小、控制精度高、成本低廉、实用性强的特点。     

电流型变换器工作原理和斜坡补偿

本文主要介绍了恒频、峰值电流检测控制方案的电流型变换器存在的问题及采用斜坡补偿来克服存在这些问题的原理及方法。     

Characteristics of MEDM for micro-holes with respect to circuit elements

Micro electrical discharge machining (MEDM) is a promising technology for fabricating micro-parts on a variety of materials. An RC circuit is suitable for MEDM because it produces low pulse width and relatively high peak current. However, it is not well understood how circuit elements affect machining characteristics of MEDM. In this paper, the effects of circuit elements on MEDM of micro-holes and the relation between characteristic variables of process and machining characteristics was investigated. Since the discharge inductance causes an increase in electrode wear and machining time, it should be minimized in MEDM. From this study, it should be less than a few μH. The machining time also increases with increasing the charging resistance. If the charging resistance is less than a few hundreds Ω, however, continuous arc discharge occurs and the machining speed is markedly reduced.     

进电方式对高阻半导体硅放电加工影响研究

进行了高阻半导体硅的放电铣削加工实验,通过检测脉冲放电电压和电流波形,对固定、旋转、随动三种进电方式下的加工情况进行了对比。结果表明：固定进电方式下,由于进电点会逐步生成不导电的钝化膜,接触电阻不断增大,回路中的总电阻不断增大,放电峰值电流逐步减小,最终导致无法加工;旋转进电方式下,由于进电电极与加工区域距离增大,导致放电回路中的体电阻不断增大,放电峰值电流也会逐步减小;随动进电方式下,放电回路中进电电极会不断刮除产生的钝化膜且极间距离维持不变,因此接触电阻和体电阻能保持始终稳定,放电加工稳定性较好。
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节能式电火花加工脉冲电源的动态特性研究

运用状态空间平均法，建立了一种节能式电火花加工脉冲电源的等效电路模型和等效传递函数模型，进而对其放电电流的动态特性进行了分析和校正。电路仿真结果和实验样机加工实验证明，该种节能式脉冲电源的动态特性满足放电电流上升速度的暂态性能和放电电流纹波大小的稳态性能两方面的指标要求，可以实现低损耗、高速、稳定的放电加工。     

PULSE DISCRIMINATION FOR ELECTRICAL DISCHARGE MACHINING WITH ROTATING ELECTRODE

This article presents a new method for discrimination of various types of pulses generated during an electrical discharge machining process in presence of a rotating electrode. Existing pulse discrimination methods do not perform efficiently in an electrical discharge machine with rotating electrode, as arcs rarely occur during the machining process. Our method involves simultaneous comparison of the gap voltage and current signals with various thresholds. The main advantage of our proposed method is its efficient computation and significantly better accuracy in discriminating between various pulse classes for electrical discharge machining devices with rotating electrode. Experimental studies demonstrate a superior performance of our method in distinguishing normal pulses from harmful arcs, open circuit and short circuit pulses, compared with the state-of-art methods.     

高频脉冲电解加工电源的研制

近些年研究发现脉冲电流电解加工比起直流电解加工有更高的加工精度,为此研制了一套以IGBT(绝缘栅双极型晶体管)作为斩波元件的全桥逆变高频脉冲电解加工电源。详述了电源的总体结构、全桥逆变电路、以SG3525A为PWM(脉冲宽度调制)控制芯片的脉冲信号发生电路及调节电路和IGBT驱动电路的原理和过程。提出了一种使用大容量IGBT作为泄流元件的快速短路保护系统。该电源可输出占空比可调,频率达40kHz,最大为2kA的脉冲电流,输出波形稳定、不失真。     

The skin-effect in ferromagnetic electrodes for wire-EDM

In wire electrical discharge machining (wire-EDM) material is removed by the thermal energy of an electric spark that has been initiated between two electrodes (the wire and the workpiece), submerged in demineralised water. The use of high frequency current pulses for sparking leads to excellent machining performance, in terms of the work piece roughness, the material integrity of the cut and the material removal rate. To reach the highest frequencies, the wire-EDM generator mostly consists of a voltage source with an as low as possible internal inductance. The working current delivered to the spark and, hence, the material removal rate of the process depends on the total impedance of the electrical circuit. In this article the importance of the wire’s impedance will be shown. Due to the skin-effect, this impedance depends on the frequency of the current signal, especially for ferromagnetic wires, such as steel wire. Coatings will prove to be primordial to prevent the machining speed from dropping significantly.     

IGBT半桥逆变式电火花加工脉冲电源

提出了逆变式电火花加工脉冲电源的工作原理,选用了半桥主回路结构和ＩＧＢＴ功率开关器件研制新型脉冲电源,总结了新型脉冲电源中高频变压器工作磁通密度、输出回路滤波电感和ＲＣ吸收网络的设计方法。工艺实验表明,新型脉冲电源在满足电火花粗、中加工性能要求的同时,将电能利用率由低于２５％提高到８０％以上,体积降低到原来的十分之一。     

INVESTIGATING THE EFFECTS OF EDM PARAMETERS ON SURFACE INTEGRITY,MRR AND TWR IN MACHINING OF Ti–6Al–4V

Ti–6Al–4V is a kind of difficult-to-cut material with poor machinability by traditional machining methods, while electrical discharge machining (EDM) is suitable for machining titanium alloys. In this paper, three input machining parameters including pulse current, pulse on time and open circuit voltage were changed during EDM tests. To investigate the output characteristics; material removal rate (MRR), tool wear ratio (TWR) and different aspects of surface integrity for Ti–6Al–4V samples such as topography of machined surface, crack formation, white layer (recast layer) thickness and microhardness were considered as performance criteria. The variations of MRR and TWR versus input machining parameters were investigated by means of main and interaction effect plots and also verified by ANOVA results. The effect of pulse energy based on pulse on time and pulse current variations against recast layer thickness and microhardness was studied. The possibility of forming different chemical elements and compounds on the work surface after EDM process was investigated by EDS and XRD analyses. The experimental results revealed that general aspects of surface integrity for machined samples are mostly affected by pulse current and pulse on time. The approximate density of cracks, micro holes and pits on the work surface is intensively dependent on pulse energy variations. Although increase of pulse energy improves the material removal efficiency but leads to increase of average thickness and microhardness of recast layer.     

节能式电火花加工脉冲电源的系统设计

在对比传统电阻限流独立式电火花加工脉冲电源和节能式脉冲电源电路结构和控制策略的基础上，提出了节能式电火花加工脉冲电源的系统设计方案，并且通过工艺试验，在检验节能式电火花加工脉冲电源加工工艺性能的同时，也考察了其系统设计的方案可行性和加工稳定性。     

Thermoelectric Model of the Cutting Process

Thermoelectric modeling is based on the profound physical analogy between heat conduction and current flow in various media. In developing the equivalent circuit, steady machining is assumed (constant spindle speed and cutter feed). That corresponds to a dc circuit. Since the current from a source is constant in any circuit conditions, a current source is used in the circuit, rather than an emf. The integral current source in the equivalent circuit corresponds to a set of thermal components. In this approach, the system consisting of the workpiece, the cutting insert, the tool holder, and the machine-tool housing may be regarded as an element in the block diagram of the thermodynamic control system for the turning of any material.