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.     

两相逆变器—感应电动机系统的分析及动态性能模拟

本文介绍了最新开发、适用于汽车蓄电池及太阳能电池供电的两相逆变器—感应电动系统。文章讨论了系统构成特点,以及与永磁直流电动机和无刷直流电动机相比所具有的优点。文章把两相逆变器和两相感应电动机作为一个整体列举了系统的数学模型,根据编制的计算机程序可以模拟系统的动态及稳态性能,与研究样机实测性能对比两者较为接近。     

Synchronous Motor Railcar Propulsion

Development of ac motor drives for rail transit car has centered on the induction motor with pulsewidth modulated (PWM) inverter control. Interest in the induction motor as a replace for the series dc traction motor stems from the simplicity of the squirrel cage rotor of the induction motor. In this article, the short-comings of PWM inverter-induction motor transit car drive are examined. It is shown that the synchronous, or brushless dc, motor drive can provide performance exceeding both the PWM inverter-induction motor and the conventional dc motor in the transit car application.     

Speed Control of a Brushless Static Kramer System

A new brushless speed control system is proposed which consists of a self-cascade induction motor and a brushless commutatorless motor. The slip power extracted from the stator terminals of the induction motor is converted to mechanical power by the commutatorless motor, which is coupled mechanically to the induction motor shaft. The field control method, the advance angle control method, and the dc chopper control method for speed variation are discussed. The experiments using a prototype self-cascade motor which has single-winding schemes both on the stator and rotor show that smooth peed variation can be achieved by dc chopper control. The proposed system offers the advantages of highly reliable, maintenance-free operation, and has less reactive power and smaller harmonic contents in supply lines than conventional systems.     

High Response Control of Stator Watts and Vars for Large Wound Rotor Induction Motor Adjustable Speed Drives

Extremely rapid control response (0.01 s) of stator watts and vars has been obtained on a 15 000-hp wound rotor induction machine with a cycloconverter controlled secondary by means of an orthogonal control scheme which linearizes the machine equations and combines both feedforward and feedback error signals. Leading and lagging power factor and positive or negative stator power flow can be smoothly and rapidly controlled over a speed range in excess of ±35 percent of the induction motor synchronous speed. This doubly fed drive may be termed a "Scherbiustat drive" because the wound rotor induction motor secondary power conversion equipment is the static equivalent of the Scherbius machine. This type of a drive does not employ a dc link in the motor secondary power conversion equipment. It should not be confused with a static Kraemer drive which employs a dc link in the frequency conversion process and was so named because of its similarity to the original Kraemer drive which uses a synchronous converter and a dc motor in the secondary power conversion process. Recently obtained field results have verified the original study results discussed herein.     

High-Performance Vector-Controlled AC Motor Drives: Applications and New Technologies

A high-performance ac motor control has been developed by employing the vector control concept. Its versatility has been proven through the six years of experience in applications to pinch roll drives of continuous casting plants, machine tool spindle drives, and other drive systems in industry. Equivalent torque characteristics are achieved with ac motors compared to dc motors without direct detection of the magnetic flux. The effect of rotor temperature on the torque characteristics has been compensated to a satisfactory level in actual industrial use by various means. Servo drives, both synchronous motor and induction motor types, have been introduced. The test results show that the performance of ac servo drives is equivalent or superior to that of the PWM-controlled dc servo drives. Furthermore, an example of the direct-drive servo is described, where an ultra-low speed high-torque motor and an ultra-high resolution position sensor play key roles. In addition, the possibility of a more sophisticated servo drive exploiting modern control theory is suggested.     

DC BRAKING CHARACTERISTICS OF DOUBLE-SIDED LINEAR INDUCTION MOTORS

ABSTRACT

An analysis of dc braking performance of linear induction motors is presented. Specific phenomena such as longitudinal end-effects and transverse edge-effects are taken into account. Computed results are compared with test results available for the dc braking characteristics of the existing largest double-sided linear induction motor.     

A Current Source GTO Inverter with Sinusoidal Inputs and Outputs

With the application of gate turn-off thyristors (GTO's) and PWM control techniques, a current source inverter capable of producing sinusoidal input/output (I/O) voltages and currents has been developed. The sinusoidally modulated current is fed to the GTO's in the rectifier and inverter sections. The overvoltage-absorption capacitors connected to the ac input and output terminals function as a filter and, consequently, the waveforms of the input/output voltages and currents become sinusoidal. Because the PWM control utilizes the high-speed switching characteristics of the GTO's, the dc link current smoothing reactor and the overvoltage absorption capacitors are greatly reduced. The dc link voltage in the rectifier section is controlled to adjust the ac motor current. This is accomplished by using the firing angle shift method in conjunction with the method involving varying the width of the bypass gate pulses, which put the rectifier section into a bypass state. The current source GTO inverter is used to drive an 11-kW induction motor. As a result, excellent acceleration and deceleration characteristics are obtained, which verifies that the new current source inverter is quite suitable for driving an ac motor at variable speeds.     

Grid models intended for investigating electric drives based on induction motors

A model of an electric drive and a grid model of an electric motor are presented. The grid model is used for forward substitution into equations of motion and the calculation procedure intended for calculation motion performance taking into consideration the electromagnetic torque is given. The electromagnetic torque is determined via a static analysis of the grid model of the induction motor operating as a stepper drive or as a drive of a dc brushless motor.     

DC Link Current Control for High-Performance CSIM Drives

A novel scheme is formulated to control the dc link current of a current source inverter induction motor (CSIM) drive which greatly enhances the current response with substantial benefits on the overall dynamic performance of the drive. In addition to conventional closed-loop control with a PI regulator, the novel scheme incorporates a function generator to compensate for the motor back-EMF seen by the dc link. Application of this scheme to an indirect field-oriented CSIM drive is presented, and improvement in the drive performance is documented.     

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.     

Development of an Induction Machine Commutated Thyristor Inverter for Traction Drives

Several designs detailing the construction of brushless cage-rotor induction machines operating at unity or leading power factor at the 35-hp level have recently been published [1]-[3]. The experimental machine combines the torque characteristics of a conventional cage induction machine with the leading power-factor (PF) capability of an overexcited dc field synchronous condenser into one unit using a common cage rotor and a common stator core. The ability of this machine to naturally commutate a high-power current-source thyristor inverter is apparent without any need for capacitors. The preferred adjustable speed propulsion arrangement consists of a mains-fed phase-delay-rectifier (PDR), high-voltage dc link, and a current-source inverter powering a ten-pole traction motor with constant V/Hz control. The drive system provides continuously variable torque during motoring, and regenerative braking modes and specific details are given for a 150-hp cage-rotor traction motor and converter, capable of natural commutation up to 200 Hz, currently under development.     

Cause and analysis of stator and rotor failures in three-phasesquirrel-cage induction motors

The squirrel cage induction motor has limitations, which, if exceeded, will result in premature failure of the stator or rotor. The authors identify the various causes of stator and rotor failures. A specific methodology is proposed to facilitate an accurate analysis of these failures. Failures of the bearings and lubrication systems are excluded     

计及频率变化的感应电动机负荷特性分析

对于异步联网系统中网架结构比较薄弱的省网系统或者系统解列后形成的孤岛,发生故障时会引起比较大的频率波动,在此情况下对感应电动机进行建模时考虑其频率特性尤为重要。基于感应电动机一阶机械暂态模型,利用解析法分别推导出不同负载特性下稳态及动态转差率关于系统频率的表达式,并在此基础上计算吸收的有功功率和无功功率,进而分析感应电动机的功率-频率特性。在MATLAB中建立感应电动机五阶电磁暂态仿真模型,仿真分析不同负载特性感应电动机的功率-频率特性。仿真结果与理论推导结果吻合,验证了在简化模型下推导得到的感应电动机频率特性解析式的正确性和有效性。     

Application of New Drive Systems for Plate Mill Drives

Recently, certain plans have been made to replace existing motors with the objective of achieving controlled rolling in Japanese plate mills. Application of ac drive systems, which are making rapid progress, can be considered for these plans. A comparison of conventional dc motors, brushless dc motors, and vector-controlled induction motors fed by cycloconverters (cycloconverter IM's) is introduced from the viewpoint of their characteristics such as power-torque curve, efficiency, and influence of harmonic current on the power system. As a result of comparison it is found that the cycloconverter IM's can be satisfactorily applied to the plate mills.     

Characteristics on PWM CSI-induction motor drive system with utility interactive photovoltaic generation

This paper proposes a PWM current source inverter-induction motor drive system with photovoltaic generation. Solar cells are inserted in dc link to obtain constant current characteristics. They are connected to the utility system with a PWM converter. The PWM converter is controlled to obtain the maximum output photovoltaic (PV) power. The PWM inverter supplies sinusoidal currents for an induction motor, which is driven by constant V/f control. A pulsewidth control is utilized in the inverter section because of constant dc link current caused by peculiar V-I solar cell characteristics. In the system proposed here, the PV power is not only used for inverter-induction motor drive but it also flows into the utility system. The experimental results in steady state show that the proposed system has sinusoidal current with unity power factor in the utility system, the maximum output PV power and sinusoidal current/voltage for a motor. The demonstrated results for the separation of the utility system or the motor from the converter-PV-inverter system are given. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (2): 79–87, 1997     

Determination of Parameters in the Universal Induction Motor Model

A systematic procedure to determine the parameters of a previously proposed low- to high-frequency induction motor model is presented. An analysis of the high-frequency behavior with regard to the impact of magnetic core selection, parasitic interturn and winding-to-frame capacitors, and skin effects of windings is investigated in greater detail for the proposed universal model of an induction motor. The model is universal in the sense that it is derived by extending the low-frequency standard T-equivalent circuit (IEEE Standard 112) to include high-frequency effects under both common- and differential-mode domains and can be used for transient reflected-wave studies and electromagnetic interference emissions in motor drive systems. A test-based method and an analytical approach, which are useful in application and design stages, respectively, are presented to determine the frequency characteristics of the induction motor. Findings of the investigation were verified experimentally with results presented in this paper.     

Dynamic Braking of Induction Motors Using DC Injection

ABSTRACT

Dynamic braking of 3-phase induction motors through dc injection in commonly used in applications such as cranes and hoists. The paper analyses the performance of a slip ring induction motor with dc injection and derives expressions for the optimum values of injection voltage and rotor resistance. Digital computer simulation of the sequence of operations like motoring and braking is also given.     

Simplified Model and Closed-Loop Control of a Commutatorless DC Motor

A simplified dynamic model of a current-fed, self-commutated synchronous motor, operating with a constant angle between the motor counter electromotive force (CEMF) and the input current. The model, which is justified experimentally, includes only two time constants, associated with the rotor inertia and the dc link inductance. This permits the design of the current and speed controlling loops along the same principles used for classical armature-controlled dc motor drives. In this way, the experience which is widely available in industry can be applied, at least with a good approximation, to design of the commutatorless dc motor drives. Various control configurations are discussed. Control loops are designed and closed around the basic motor-inverter block. An experimental result is obtained for each control configuration, thus validating the proposed model.     

PERFORMANCE ANALYSIS OF LOAD COMMUTATED INVERTER FED CAGE INDUCTION MOTOR DRIVE

ABSTRACT

An approach, to analyse the performance of a variable speed cage induction motor drive fed from load commutated inverter (LCI), is presented. Induction motor with an appropriate capacitor across its stator terminals constitutes the load on the inverter. A fully controlled bridge converter, supplied by a variable dc voltage source, commutated with the back emf of the motor, acts as an inverter. An algorithm to compute the motor performance, is developed using equivalent circuit representation of the system. Strategies for the selection of control variables, in order to achieve the desired speed range for satisfactory performance of the drive are given. The performance of a 3-hp, cage induction motor fed from LCI is computed, using the developed algorithm for wide range of speed; and is verfied experimentally.