On the Regenerative Braking of DC Motors with AC Supply

A new method is described in which the dc motor may regenerate power effectively to ac supply. The principle is similar to that with a dc chopper for regeneration of the power from dc motor to dc supply. In this new method, however, thyristor switches synchronizing to the ac supply are used instead of a dc chopper. The principle and the power calculations as well as experimental results are presented. From theoretical and experimental considerations it is clarified that there exist suitable trigger angles in the thyristor of the synchronizing switches.     

Computer-Aided Analysis of a Multiphase Chopper-Driven DC Series Motor and Test Results on a Microprocessor-Based Three-Phase Chopper Drive

A comprehensive digital computer-based analysis using a state-space model which predicts the performance of a dc series motor controlled by a multiphase chopper is presented. The analysis is based on the formulation of system equations in multivariable state-space form and takes into account the nonlinear magnetization curve and the variation of field inductance with load current. The predicted results based on this analysis are shown to agree with the test results on a practical drive system developed for this purpose in which the dc series motor is driven by a microprocessor-based three-phase thyristor chopper. The control circuit development for the practical drive is briefly described.     

Frequency and Current Ripple of DC to DC Power Converters with Respect to Different Modulation Techniques

In connection with dc choppers, different modulation techniques are used. The chopper may be of a transistor bridge type or of any thyristor type. The output current and voltage can be controlled by pulsewidth modulation, pulse-frequency modulation, or two-level control of the load current. The steady-state behavior of the different modulation techniques is shown in comparable equations and diagrams. Also shown are the ranges of the parameters in which it is possible to use the approximate equations for the chopper frequency and the output current ripple.     

Newly Developed Thyristor Chopper Equipment for Electric Railcars

In the chopper control system for electric railcars, it is effective to adopt high operational frequency of the chopper for achievement of the following: 1) decrease of higher harmonic current induced in the trolley wire, 2) reduction of weight for reactors and capacitors in the traction circuit, and 3) improvement of control response. Through development of reverse-conducting thyristors with very short turn-off time and a repulsion type two-phase chopper, we finally realized production of a new standard high-frequency chopper equipment with regenerative braking for 1500-V dc railcars. Technical achievements mentioned previously were completely realized as a result of adoption of high frequency, 660 Hz, in the equipment. The newly developed standard high-frequency chopper equipment for 30 cars were delivered to the Chiyoda Line of Teito Rapid Transit Authority in Tokyo, and they have been operated satisfactorily in revenue service since March 1971. This paper also describes: 1) the chopper circuit using fast-switching reverse-conducting thyristors and series saturable reactors, 2) analysis of commutation circuit and methods of suppressing reapplied forward voltage increasing rate (dv/dt) and shortening commutation period, 3) the composition of the traction circuit including the protection system, such as protection for overvoltage at the regenerative braking, and 4) test results on the Chiyoda Line of Teito Rapid Transit Authority.     

A DC Motor Control System for Electric Vehicle Drive

A control system of a dc separately excited motor for electric vehicle drive is described. The armature of the motor is controlled by a thyristor chopper, whereas the field is regulated by a highfrequency transistor chopper. The control scheme combines the advantages of both series and shunt motors and permits maximum possible acceleration within the transient thermal ratings of the motor. In addition, motor torque becomes smoother under all operating conditions. A complete drive system has been formulated, designed, and analyzed, and performances have been evaluated on a hybrid computer. At present, the breadboard of the drive system is being tested in the laboratory.     

Thyristor Commutation in DC Choppers? A Comparative Study

The typical dc chopper motor controller consists of two thyristors, two or three diode rectifiers, a commutating capacitor, and one or more commutating inductances. The major art in circuit design is selecting the most suitable configuration for the given application, particularly the location of the inductances. It is desirable to minimize the inductance in certain loops and to carefully choose the inductance in other loops. A computer-aided analysis and optimization technique has been applied to several attractive chopper circuits. It appears that inductance in series with the auxiliary thyristor favors turn-off of the main thyristor at the expense of the auxiliary thyristor and vice versa. The best arrangement has most of the commutating inductance in a path that is common to both thyristors. Where one of the thyristors has a diode connected directly across it, there is generally an optimum value of inductance which yields maximum turn-off time. If no such diode is used, the maximum turn-off time is obtained when the inductance is zero.     

直流回馈型直流电子负载的设计与研究

针对机车电源测试时用模拟负载造成能量浪费的情况,设计了一种将测试能量回馈到电源直流输入侧的能量回馈型电子负载。该电子负载由升压斩波电路和移相全桥电路级联组成。前级升压斩波电路采用单电流环控制结构,单周期控制方式,通过控制输入电感电流模拟直流电源的输出特性;后级移相全桥电路采用输入电压外环、输出电流内环的双闭环控制结构,比例积分控制方式,通过高频逆变实现输入与输出的电气隔离,并将能量高效率的回馈给测试电源的直流输入侧,使测试能量被循环使用。通过8 k W实验平台的仿真与实验,验证了设计的可行性,结果表明电子负载能节约超过80%的测试电能。     

Using Inverters for DC Motor Control

In recent years the chopper circuit has been widely recognized as the most reliable and economical means of dc control. This work deals with a parallel possibility that uses ac inverters instead of chopper circuits. A detailed analysis is given for the bridge-type inverter. Some experimental results of this application for driving dc motors are presented.     

Thyristor DC Switch Inverter

The thyristor inverter induction motor drive devised, analyzed, and experimentally evaluated in this investigation has a new thyristor commutating technique where the dc bus current is interrupted periodically by a thyristor dc switch to commutate all the inverter thyristors.     

Estimation of Critical Inductance for DC Separately Excited Motor Fed by Load-Dependent Chopper

ABSTRACT

This paper describes a method to estimate the value of a critical inductance for a dc separately excited motor fed by load dependent chopper to eliminate the discontinuous conduction of armature current. A trapezoid approximation has been used to estimate the value of the commutation time of the chopper. To verify the suitability of the method, the performance equations corresponding to different intervals of a chopping cycle are solved numerically on a digital computer. The value of critical inductance has also been obtained using the method developed for rectangular wave chopper. It is found that the proposed method predicts more accurate value of the critical inductance than that of a rectangular wave chopper. It is also seen that a much larger value of the inductance is needed to eliminate the discontinuous conduction in dc separately excited motor fed by load dependent chopper than using rectangular wave chopper.     

An improved PSPICE model for simulation and analysis of thyristorcommutation circuits in DC choppers

An accurate model of the thyristor in DC chopper commutation circuits is described using the available elements in the PSpice program library. The improved model, which takes into account the reverse recovery time during turn off, is used to simulate voltage and current commutated DC choppers. Simulation results, which include a study of commutation failure, agree with theoretical and experimental results. The model developed is useful for computer aided analysis and design of DC thyristor choppers including the commutation circuits     

High-current DC choppers in the metals industry

The chopper rectifier system converts AC power to DC power. The system rectifies AC power by utilizing a step-down transformer and unregulated diode rectifier to provide a bulk DC bus. The chopper circuit modulates the current from the bulk DC bus to provide a regulated output. This paper describes how DC-chopper systems have many operational benefits over conventional diode or thyristor rectifiers     

A New Speed-Control System for DC Motors and its Application to Elevators

A circuit with a unidirectional armature current and bidirectional field current was used in order to realize a high-reliability speed-control system for dc motors by simplifying the armature circuit construction in comparison with conventional Thyristor-Leonard speed-control systems. In making the new circuit feasible, we developed a system in which either armature current or field current is fixed and the other varies depending on the magnitude of the torque command; a high-reliability magnetically controlled three-phase thyristor amplifier; and minor feedback loops provided with a field current control circuit and armature current control circuit. By using these techniques, we developed a dc motor control system that features higher reliability and smaller power consumption than conventional control systems. The new system was applied to elevator control with good results.     

2.5 kV 2000-A monolithic reverse conducting gate turn-off thyristor

A 2.5 kV 2000 A monolithic reverse-conducting gate turn-off thyristor (RC-GTO) has been developed using a precise lifetime control technique, a precise gate etching control technique, and an electrical separation technique between the GTO part and the diode part. It is most important for the RC-GTO to separate electrically the GTO part from the diode part. A very high separation resistance of 100-150 Ω is attained by applying a double diffused profile, and a high turn-off current of 2000 A is achieved by applying the precise lifetime control technique and the precise gate etching control technique. The development of the 2.5 kV 2000 A RC-GTO has been aided by the use of computer simulation and an image-converter camera     

DYNAMIC MODEL OF CHOPPER FED DC SEPARATELY EXCITED MOTOR

ABSTRACT

This paper describes the transient response of a chopper fed dc separately excited motor using time ratio control. An approximate second order model for predicting the transient behaviour of the motor is developed using perturbation technique. The transient response for small and sudden variations of duty interval and load torque is deduced during discontinuous and continuous current mode operations. The effect of external inductance on the performance of motor in the armature circuit has also been investigated. The results are compared with those obtained from a digital computer by numerically solving the simultaneous differential equations valid for different intervals of chopper cycle and also with the first order model. It is shown that the second order model is more accurate than the first order model and much simpler and efficient than the numerical approach. The theoretical results obtained are also verified with an experimental set up. Experimental results closely agree with theoretical predictions.     

Triacs in Reversible Regenerative DC Motor Drives

This paper presents a triac converter which can replace two thyristor bridges normally used for regenerative dc motor drives. The most important characteristics of the triac are outlined and specific problems are discussed. Performance specifications for the control electronics are given. An experimental drive is presented and some run measurements are shown.     

Design Analysis of Multiphase DC Chopper Motor Drive

DC chopper propulsion speed control is attained by a solid-state switch whose variable on-off duty cycle transfers a proportional quantity of pulsed energy into a motor. The pulsed battery current is alternately stored and expended within the dc motor and its series connected dc choke during each period of conduction and succeeding freewheeling operating mode. Hence an energy transfer is maintained transforming a high voltage low dc supply into a lower voltage higher dc demanding load. The transformation ratio is considered a controlled variable by simply controlling the on-off conduction duty cycle of its solid-state switch. This simplistic approach, however, fails to recognize that the instantaneous battery current amplitude equals the motor current demand during the switch ``on' period resulting in potentially very large peak power demands [1].     

A DSP-based modified slip energy recovery drive using a 12-pulse converter and shunt chopper for a speed control system of a wound rotor induction motor

This paper introduces a modified slip energy recovery drive system for speed control of a wound rotor induction motor offering improvement of drive performance, particularly line power factor and overall system efficiency. A 12-pulse line commutated thyristor converter operating in an inverter mode in conjunction with an additional IGBT shunt chopper is employed to transfer slip energy back to ac mains supply via three phase transformers. This approach offers motor speed control by varying the duty cycle of the chopper instead of changing the inverter firing angle. As a consequence, supply power factor can be improved. The servo state feedback designed by linear quadratic regulator (LQR) with observer is also included in order to keep motor speed to be constant over a certain range of operating conditions by using the estimated dc link current derived from motor speed. The advantage of this technique is absence of current transducers for current feedback control loop. The overall control system is implemented on DSP, DS1104’TMS320F240 controller board. Experimental results are illustrated in order to validate performance of the proposed system.     

A Microprocessor-Based Position Control of a DC Drive Taking into Account the Load's Variations

The position control of a dc motor is presented. This motor is fed by a four-quadrant chopper. The control is entirely digital and is assumed by a microprocessor. This motor is one of a robotic manipulator joint's actuators. A model of the drive taking into account the mechanical structure variations of the load is presented. This model leads to use of an affine-state algorithm which is implemented on the microprocessor.     

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.