Selection Criteria for Servo Motor Drives

The power density and acceleration characteristics of the ac servo drive are being recognized as being superior to those of the dc counterpart. The ac servo family consists of permanent-magnet synchronous, dc brushless, induction, and switched reluctance motor drives. This ac servo family is comprised of radial (also known as the sausage type) and axial (also known as the pancake type) field motors, thus enlarging the spectrum of ac servo motors to the users. Realizing that the ac servos are of recent development, it is obvious that their potentials and pitfalls have not been published, thus making it difficult for the user and application engineer to choose one servo from the family of ac servos for a particular application. In this regard, an attempt is made here to develop a set of selection criteria to differentiate the various servo drives of the ac family. The factors proposed to do that are cost, power density, acceleration rates, peak torque capability, speed range, torque per unit ampere, thermal capability, parameter sensitivity, cogging torque, ripple torque, braking, rotor position feedback device, etc. Application of these criteria would promote appreciation for the various facets of ac servos through their comparison with other drive types.     

Electric Drives (Boldea, I and Nasar, S.A.; 2006) [Book Review]

The new enlarged second edition of this excellent textbook presents the latest concepts and basic electrical drive technology including vector and direct torque control of ac motors and generators. Some of the topics covered in the book's 15 chapters include: energy conversion in electric drives; electric motors for drives; power electronic converters for drives; dc brush motor drives; controlled rectifier dc brush motor drives; synchronous motor for drives; PM and reluctance synchronous motor drives; switched reluctance motor (SRM) drives; practical issues with PWM converter motor drives, large power drives, and an entirely new chapter on control of electric generators. Each chapter is supplemented with adequate, well-selected examples, summary, problems, and selected references at the end. An important advantage is an attached CD that includes test browsing, PowerPoint slides, and Matlab-Simulink programs with eight selected dc and ac closed-loop drives. The book is recommended as a basic text to a wide audience of engineering educators, students, and engineers in industry.     

有效平滑无刷直流电机转矩的新方法

在无刷直流电机(Brushless DC Motor,简称BLDCM)数学模型的基础上,分析了传统PWM调制方式对BLDCM非导通相引起续流电流的原因,以及该续流电流导致非换相期间的电磁转矩脉动的现象.通过原理分析及数学推导,提出在三相逆变桥输入端加上前级直流变换器,以控制电机的新策略.该方法在理论上消除了BLDCM在非换相区内的转矩脉动,并且利用试验证明了该方法的有效性.     

基于级联式拓扑的消除无刷直流电机传导区转矩脉动方法

在无刷直流电机的数学模型基础上,详细分析了传统的H_PWM-L_ON调制方式对BLDCM的非导通相引起续流电流的原因,以及由此续流电流导致非换相期间(传导区)的电磁转矩脉动的现象.通过原理分析及数学推导,提出在三相逆变桥入端加上前级直流变换器,利用单一直流母线电流的反馈闭环来控制电机的新策略.该方法在理论上彻底地消除了BLDCM在传导区内的转矩脉动,并且利用试验证明了此方法的有效性和可行性,说明比较适合用高精度要求下的无刷直流电机控制系统.     

A Sinusoidal Pulsewidth Modulated Three-Phase AC to DC Converter-Fed DC Motor Drive

The external performances such as power factor, displacement factor, harmonic factor, and ripple factor of a three-phase ac to dc converter-fed separately excited dc motor drive employing sinusoidal pulsewidth modulation (SPWM) control technique are obtained for different speeds and modulation indexes. Since separately excited dc motors with armature voltage control provide constant torque operation, the external performance is also determined for the drive motor operating at different values of constant load torque. Motoring and regenerating operations of the dc drive machine are considered. The three-phase PWM converter-motor drive system is analyzed, taking commutation effects into account in motoring and regenerating operations. The analysis has revealed 27 common modes in one repetitive period of the output voltage. The sequence of modes for all pulses in one period of the output voltage is established. Experimental oscillograms of typical waveforms from a laboratory-sized dc motor are illustrated to verify the basic principles of operation. Although the converter circuit requires some additional components in comparison with the commonly used phase-controlled converter, the improved performance characteristics make it attractive for industrial applications involving large power ratings.     

An Application of Two-Phase DC Chopper Motor Drive

During the past ten years the Army has invested a sizable effort into new systems configurations and development programs to improve ground vehicle mobility. United States Army Mobility Equipment Research and Development Center (USAMERDC), Fort Belvoir, Va., has been particularly interested in an improved vehicle mobility for off-highway vehicles, amphibians, and engineer equipment through electrical propulsion. Such drive systems incorporating individual wheel controls provide improved mobility over all types of terrain, simplified supply logistics, and permit a more functional vehicle design and construction. Past experience in industry and in the government has shown that the dc motor propulsion drive is inherently simple to install and to maintain. The dc motor is somewhat heavier than comparable ac motors due to motor speed limitations; however, the dc machine, particularly the series field motor, requires relatively simple power controls since the power is processed by the motor's own commutator. Commercial dc traction motors have an inherent high-torque starting characteristic which is mandatory for engineer-type vehicle propulsion applications. In the midspeed range however, presently available dc motor propulsion drives under consideration for the Anny have unsatisfactory acceleration performance when compared to conventional mechanical drive systems comprised of a spark or compression ignition engine and a multispeed transmission. In this context, the paper discusses this Center's experimental solid-state controller and the method employed to improve the acceleration or peak power propulsion profile of an electric vehicle drive using dc series field motors.     

DC Kiln Drive Motors

The most important considerations in applying dc drive motors and thyristor power supplies to a cement kiln are their procurement, maintenance, and operating costs; and equipment reliability in the cement plant environment. Drive requirements and their effect on motor size are discussed. Efficiency comparisons at several speeds for three different designs of dc drive motors are made. Two motor kiln drives with motors connected in series and also in parallel are discussed. Recommendations for applying each connection with regard to drive horsepower and voltage are made. Included is a brief discussion on applying dc motors by taking a part of the total speed range as constant horsepower rather than taking the entire speed range as constant torque.     

TEST PROCEDURE FOR VERY HIGH SPEED SPINDLE MOTORS

Abstract

In the last ten years, the new power electronic devices and the new control techniques have allowed to open new application fields for adjustable speed/torque electrical drives. Although the traditional dc drives keep still the market supremacy, the new ac drives have performance really attractive and some additional benefits due to the machine structure and to the maintenance costs. Usually, ac drives use induction or brushless motors and the power amplifiers are driven by variable voltage/frequency in order to obtain variable speed. The authors deal with induction motors fed by non conventional supplies at very high frequency. In order to evaluate the total motor losses and the single items, a test bench with a synchronous machine capable to work up to 2 kHz with sinusoidal output voltage has been set up. As a consequence, an induction motor equivalent circuit with parameters depending on the frequency has been proposed. Today, the empirical procedure is that to use for high frequency applications shelf motors derated of a factor 10 to 20 % in order to keep into account the extra harmonic losses. On the other hand, the authors propose to design ‘ad hoc’ the motors for six-steps continuous operation in order to get about the same efficiency of standard motors. The new proposed motor equivalent circuit together with the test procedure seem to be a practical tool in order to aid the new motor design.     

Solid-State AC Drives: New Reliability for Packaging Equipment

Today's low cost variable frequency inverter drives combined with standard three-phase ac motors, eliminate downtime and maintenance of mechanical speed changers, dc motor armatures, and brushes. Advances in power semi-conductor technology makes the ac drive cost competitive with traditional variable speed drives.     

汽车EPS系统用电动机综述

电动机是汽车电动助力转向（EPS）系统中的关键部件。本文综述了在汽车EPS系统中所用到的若干电动机,包括直流电动机、伺服电动机、力矩电动机、开关磁阻电动机及交流电动机等,描述了它们的原理、助力效果和优缺点。     

AC Drive System for Tension Reel Control

Recently, adjustable-speed ac drive systems have been employed successfully for blowers, pumps, table rollers, etc., in steel plants instead of the more conventional dc drives. In processing lines many drives require speed and tension control. To confirm the suitability of an ac drive for tension control, the tension reel of an existing pilot processing line has been equipped with an adjustable-speed ac drive. An ac drive system for tension reel control, its characteristics, and performance are described and compared with a dc tension control.     

高性能高精度力矩电机伺服控制系统设计

大扭矩力矩电机是高档数控机床的关键基础部件,其伺服系统控制性能优劣直接影响机电设备的控制质量.文章简要介绍了大扭矩力矩电机的基本控制特性,着重介绍了一种基于大扭矩力矩电机的全数字伺服驱动器的控制单元构成和功率电路设计,其中采用F2812 DSP作为控制芯片.实际运行结果表明,伺服系统设计合理,性能可靠,达到了高性能、高精度的要求.     

Control Means for Minimization of Losses in AC and DC Motor Drives

Motor drive losses can be reduced considerably by independently controlling the voltage and frequency for ac motors, and the field current and armature voltage for dc motors for any torque and speed operating point. The quantities to be controlled are already accessible in inverter ac power supplies and phase-controlled rectifier dc power supplies. The control signals can be supplied by an open- loop controller which solves the loss minimization equations using preset drive parameters, or by an optimizing controller that measures or calculates the losses and finds the combination of quantities that minimizes the losses.     

Synchronous and Reluctance Motors in Position Servo Loops

At the present state of the control art, it is economical to replace dc motors in servo systems with ac synchronous and induction motors, in spite of the generally more complex circuitry induction motors, in spite of the generally more complex circuitry required by the ac principle. This report deals with synchronous motors that rely on shaft position reference to fit them into high-performance position feedback systems. It is shown analytically that any synchronous motor, including the reluctance motor, becomes a direct replacement for a converter driven dc motor if the phase voltages are the result of properly modulated shaft resolver outputs.     

AC Drives in Traction Applications

DC motors and drives have previously been the choice for traction applications. The desire to use an induction motor in similar applications has been unfulfilled due to the absence of a suitable ac drive controller that could fully exploit the economical, rugged, and simple ac induction motor. AC drives using vector-control techniques are available to gain the high-performance operation in precise-torque and four-quadrant applications. This paper describes the use of such a drive for locomotion of large coal-handling equipment.     

Application of Gate Turn-Off Thyristors in 460-V 7.5-250-hp AC Motor Drives

A 7.5-250-hp range of variable-frequency ac motor drives has been under development at the Westinghouse R & D Center since early in 1981. Design and performance details for prototype equipment rated for 10, 20, and 50 hp will be discussed. The drive system comprises a three-phase thyristor controlled ac/dc converter in conjunction with a dc/ac adjustable-frequency inverter using gate turn-off thyristors (GTO's). The output of the inverter is a six-step voltage wave in the range of 6-120 Hz, suitable for driving three-phase ac induction or synchronous motors. Details of the inverter design, including means to protect the gate turn-off thyristors from output line-to-line or line-to-ground short circuits, will be given special attention.     

Digital Simulation Of A Vector Current Controlled Axially-Laminated Anisotropic (ALA) Rotor Synchronous Motor Servo-Drive

ABSTRACT

It has been recently demonstrated that axially laminated anisotropic (ALA) rotor reluctance motors have high torque density, power factor and efficiency due to unusually high L_d/L_q ratios. For variable-speed vector-controlled drives no starting cage on the rotor is required. Through digital simulations this paper explores the steady-state torque and power factor capabilities and the transient performance of a vector ac current-controlled ALA-rotor motor drive. Fast torque and speed responses are demonstrated for a two-pole motor up to a speed of 2500 rpm. Good performance down to 0.1 rpm is obtained through an adaptive proportional integral (PI) speed controller.     

非理想反电动势无刷直流电机的转矩脉动抑制仿真研究

在伺服系统中要求电机转速平稳,抑制转矩脉动是实现转矩平稳的关键,而非理想反电势会引起较大转矩脉动。为了有效平滑无刷直流电机转矩,分析了两种不同的方法：根据定子电流和反电势与转矩表达式的关系,对于一台给定的电机,只要其反电势一定,通过优化定子电流就可以消除主要的转矩谐波分量,从而达到减小转矩波动的目的;通过坐标变换在厶=0时求解产生恒定电磁转矩所需的q轴电流,并在dq坐标系下通过矢量控制对q轴参考电流进行跟踪实现转矩脉动抑制。利用MATLAB／SIMULINK仿真平台建立系统的仿真模型,对系统模型进行仿真和分析并比较了这两种方法的特点,为实际电机的控制提供了研究方向。     

开关磁阻电动机直接转矩控制的研究

直接转矩控制(DTC)在交流电机驱动系统中是一种较完善的控制理论.事实证明它能很容易的控制电机的转矩和转速,并能减小转矩脉动.但是以前通常认为交流DTC方案不能应用于非正弦激励的SR电机.将直接转矩应用到开关磁阻电机的控制上,解决了SR电机转矩脉动问题.仿真及实验结果表明,这种控制策略不但可以有效地抑制SRM转矩脉动,同时控制简单、实时实现时只用低成本的微处理器即可.     

A Multimicroprocessor-Based Fully Digital AC Drive System for Rolling Mills

Theoretical considerations are given for a control scheme to decrease voltage disturbances in a cycloconverter-fed ac drive system, using a form of the vector control concept. The theory has been applied to a multimicroprocessor-based fully digital 72-arm cycloconverter-fed 5000-kW squirrel-cage induction motor drive control system. For speed and position sensors, a high-resolution sine encoder which generates a 15 000-sine wave/r has been developed to achieve high-performance speed regulation, particularly at ultra-low speeds. The factory test results compare far more favorably than those attainable using dc drives. They reveal that the ac drive system is suited to practical applications in main drives for rolling mills, including tandem cold mills.