DC Traction Motors Research Articles

Real-Time Implementation and Control of Multi-Source Electric Vehicle Traction Motor under Various Drive Conditions

The hybridization of multiple energy sources is crucial for electric vehicles to deliver the same performance as modern fossil fuel-based automobiles. This paper presents a torque and speed control strategy for an electric vehicle DC traction motor by regulating the power flow from two energy sources, namely battery and supercapacitor systems, to resist unpredictable disturbances. A control system with three control loops is applied to regulate the speed of the traction motor. The outer speed control loop is a nonlinear state feedback controller with a disturbance observer, which is capable of handling non-linear systems with unpredictable disturbances. The inner voltage and current control loop are precisely tuned PI controllers. Using an adaptive energy management method that varies depending on the state of charge of the source, the total reference current needed to support the load demand is split between two sources. A laboratory prototype system model is generated, and the performance is analyzed under motoring and regenerative braking conditions. For monitoring and controlling the system, the dSPACE DS1202 real-time simulator is employed. The performance of the proposed control system is evaluated and it is found that the settling time to settle within a tolerance band of 1% is 0.75 s.

Increasing reliability of traction electric motors of diesel locomotives taking into account thermophysical parameters of insulation and armature winding conductors

Introduction. The issue of ensuring the operable state of the DC traction motor is relevant due to its large-scale use on diesel locomotives, including modern powerful motors, operating on lines with increased train masses. At present, a rather difficult situation has developed in the locomotive industry with the failure of diesel locomotive traction electric motors due to a decrease in the insulation resistance of the armature windings of the electric motors and their subsequent breakdowns: up to 28 % of the total number of failures of electric motors are due to breakdown of the hull insulation and interturn short circuit of the armature and 13 % of cases are due to reduction in the resistance of the insulating material.Materials and methods. The paper considers the main directions of scientific research on the causes of insulation integrity failure, which lead to unscheduled repairs of traction motors. The theoretical substantiation of the root causes of insulation destruction is based on the importance of taking into account the coefficients of thermal linear expansion of copper and its insulating materials. In order to study thermodynamic processes in the winding of a traction motor, a computational finite element model of a winding coil laid in the groove of the armature core has been developed. The winding model is represented separately by a conductor and insulation, between which contact conditions are specified. The conductor of the calculation model heats up to 120 °C from the current flow. Mathematical apparatus embedded in the MSC calculation program, Patran – Nastran, made it possible to evaluate the deformation of the conductor relative to the insulation as a result of a linear increment due to thermal expansion.Results. With the help of mathematical modelling and based on the results of finite element analysis, the confirmation of the theoretical justification is clearly shown. The difference in elongation during heating of the motor armature conductor and insulation, obtained by mathematical modelling, is 0.6 mm and is significant for the winding (consisting of a conductor and insulation), which is usually considered as a single whole body.Discussion and conclusion. The obtained result shows the need for more detailed studies to select the technology for the insulation of the DC traction motor. The use of insulating materials for the armature winding with coefficients of thermal linear expansion equal to the coefficient of thermal expansion of the copper conductors of the winding will improve the reliability of traction electric motors of diesel locomotives in operation.

INCREASING THE ENERGY EFFICIENCY OF THE AC ELECTRIC LOKOMOTIVE TRACTION DRIVE

The study of the energy characteristics of the active traction converter with pulse-width modulation as part of the traction electric drive of an AC electric locomotive was held during the research. Active traction converter provides pulse-width control of the collector DC traction motors voltage and belongs to the basic AC / DC circuit. The transient process when switching transistor switches is accompanied by significant voltage surge, due to the scattering inductance reaction of the traction transformer. Studies have shown that the diode discharge buffer circuits do not provide discharge of the electromagnetic energy accumulated in the winding of the transformer. An active traction converter control algorithm has been developed, which implies the use of pulse-width and phase regulation of rectified voltage. Switching of transistor switches occurs in the presence of a parallel current circuit. This creates the conditions for the discharge of electromagnetic energy accumulated in the secondary winding circuit of the traction transformer. The developed mathematical model allows to investigate the electromagnetic processes that occur during the switching of transistor switches and to evaluate the energy efficiency of the electric locomotive with active traction converter. In the simulation process, the influence of active traction converter parameters and control algorithms on the power rate of the converter, the total THD distortion rate of current and voltage and the relative values of the rectified voltage were investigated. Measures to increase the power rate and to reduce the emission level of higher current harmonics into the traction network were proposed.

Deep Attenuation Use for Traction Motors of Mainline Electric Locomotives

Purpose. Given the need to improve the performance of modern mainline rolling stock, the authors analyze the possibility of using deeper regulation of attenuation. Methodology. The analysis of the operation of the thyristor-pulse converter of ER200 electric train is performed. It is established that in the acceleration mode at the limit traction characteristic it is necessary to consider two zones: the zone of constant value of traction force and the zone of constant power. A method for determining the minimum value of the attenuation coefficient for different types of DC and PC traction motors was proposed. The methods of theoretical research and analytical calculation of electrical circuits, theoretical foundations of electric traction, mathematical modeling of electrical and energy processes were used for the analysis. Findings. The complex of theoretical research and calculations allows confirming the technical possibility of deep attenuation use to regulate the speed regulation and obtain additional across-the-line positions for the rolling stock with DC and PC traction motors. The minimum attenuation coefficient value for different types of traction motors was determined. Originality. The methodology for determining the minimum value of the attenuation coefficient for traction motors of main electric locomotives in terms of using deeper magnetic flux control, replacing the use of experimental research data with theoretical studies. The essence of the studies is to form the required type of the limit traction characteristics by reducing the minimum permissible value of the excitation coefficient, which will reduce the electricity consumption. The research on determination of quantitative indicators of electricity consumption for the analysis of energy saving reserves on the main transport was further developed. Practical value. The results of theoretical research can be the basis for the modernization of main electric locomotives of direct and pulsating current with the systems of deep attenuation regulation. The research conducted will make it possible to create recommendations on designing the systems of magnetic flux regulation for traction engines with the improved technical and economic characteristics which are capable to increase the transport process efficiency on the main transport.

Increasing the energy efficiency of auxiliary machines of AC electric locomotive

Currently, an asynchronous variable frequency drive based on semiconductor converters is widely used due to the relative simplicity and reliability of the design. The use of digital microprocessor systems ensures high accuracy and flexibility of drive control. On the domestic rolling stock, the widespread introduction of asynchronous motors began to replace DC traction motors with sequential excitation. In particular, scalar-controlled asynchronous motors are used on serially produced 2TE25A diesel locomotives and EP20 electric locomotives. The auxiliary asynchronous machines of these locomotives are controlled by the vector control method. The use of a new type of engine on the rolling stock makes it possible to achieve a significant increase in the quality of consumed energy and reduce the consumption of electricity for traction of trains. Ensuring the energy efficiency of the drive in a wide range of loads requires further research. In this regard, the issue of saving energy resources becomes very urgent. The article proposes a vector control scheme for asynchronous motors of auxiliary machines of an electric locomotive, which implements an extreme method of control according to the criterion of minimizing the consumed current. The analysis of the engine operation is carried out based on its mathematical model in a rotating coordinate system d — q, which is implemented in the MatLab/Simulink software package. As a result of simulation modeling, it was found that the extreme control system with a variable step allows for each fixed value of the electromagnetic moment of the motor in the minimum time to find the optimal (extreme) value of the magnetic flux of the motor rotor, which corresponds to the minimum value of the stator current. The developed model of the motor with vector control is supplemented with an extreme regulator device, which allows achieving the best energy performance of the motor and reducing electrical losses in all operating modes with a minimum search time. The presented research results can be used in the development of energy-saving control systems for an asynchronous motor.

Design of a direct current motor with a windingless rotor for electric vehicles

Modern electric vehicles typically exploit synchronous motors with magnetoelectric excitation as traction engines. While possessing a series of undeniable advantages, the synchronous motor has one significant drawback ‒ the high cost predetermined by the high price of permanent magnets. In addition, the impossibility to disable a magnetic field in case of engine malfunction can lead to an emergency on the road. Given this, there is a need to design new structures of electrical machines with electromagnetic excitation. The structure of a DC traction motor with electromagnetic excitation involving the rotor or stator segmentation makes it possible to considerably weaken the field of the armature transverse reaction by decreasing magnetic conductivity of the magnetic circuit in the transverse direction. Therefore, such a structure lacks commutating poles and a compensation winding. There are no permanent magnets in the structure, all windings are stationary, an electronic switch is used instead of a collector, and a windingless low-inertia rotor does not require additional measures to remove heat. That all has made it possible to significantly reduce the cost of active materials for the traction engine and improve its reliability. To test the performance of the new design, a full-size model of the engine and a working experimental prototype were fabricated. Applying a synchronous jet engine with magnetization for the BMW i3 electric car as an analog, the engine calculations were performed and its simulation was carried out. The results of the analysis show that the mass of the new engine is 35 % greater than the mass of the analog but the cost of active materials is less than that of the analog by 63 %. The results testify to the possibility of implementing a given structure industrially

Performance Control of the Commutator-and-brush Assembly of the Traction Motor

The operation of the commutator-and-brush assembly largely influences the operational reliability of DC traction motors. Unsatisfactory operating conditions of the commutator-and-brush assembly lead not only to a deterioration in the current collection and damage to the contact surface, but also to a change in the switching setting. Switching quality control must be carried out simultaneously both by the product of the average and average integral durations and by the maximum duration of arc pulses. The paper considers the influence of the quality of commutation on the reliability of the operation of the commutator-and-brush assembly of the traction motor. A method is proposed for assessing the degree of sparking by the duration of arc discharges in comparative tests of electric machines of the same type, which makes it possible to characterize the reliability of the operation of the commutator-and-brush assembly and to take into account all types of causes of commutation failure: both electromagnetic and mechanical ones.

Методика определения допустимых режимов работы тягового двигателя постоянного тока карьерного самосвала для обеспечения удовлетворительной коммутации

The article considers an approach to determining the permissible ranges of changes in the armature voltage, armature current and the excitation coefficient of the DC traction motor of a mining dump truck to ensure satisfactory commutation. When the DC motor is running in the specified modes, the probability of sparking in the collector-brush unit with a degree of 2 points will be minimal. A method for determining the permissible operating modes of a mining dump truck traction motor to ensure satisfactory commutation is proposed. The method allows, based on the analysis of experimental data, to determine the permissible ranges of changes in voltage, armature current and excitation coefficient, at which the degree of sparking does not exceed 1½ points

High voltage gain dual‐input dual‐output DC‐DC converter with reduced voltage stress on semiconductors

SummaryThis paper proposes a new nonisolated multiport DC‐DC converter with two inputs and two outputs with different voltage levels. Different energy sources with distinct voltage‐current characteristics can be utilized as the input sources. Regarding multiple outputs, the proposed converter can be utilized in electric vehicles (EVs) to supply the DC traction motor and the auxiliary loads. The main advantages of the proposed converter include the high voltage gain with small values of the duty cycles, low normalized peak voltage stress (NPVS) across the semiconductors, and the continuous input currents. The voltage stress across the semiconductors is lower than the maximum output voltage. This feature makes it possible to use the switches with low turn‐on resistance and the diodes with reduced rating voltage. Performance principals of the proposed converter along with the steady‐state analysis, such as the derivation of the voltage gains, voltage and current stresses of the semiconductors, etc, are carried out. Experimental measurements made for the laboratory prototype of the proposed converter confirm the theoretical analysis.

Моделирование процесса коммутации тягового двигателя постоянного тока карьерного самосвала

Моделирование процесса коммутации тягового двигателя постоянного тока карьерного самосвала

МОДЕЛИРОВАНИЕ РЕЖИМОВ РАБОТЫ ТЯГОВЫХ ЭЛЕКТРИЧЕСКИХ ДВИГАТЕЛЕЙ ПОСТОЯННОГО ТОКА

МОДЕЛИРОВАНИЕ РЕЖИМОВ РАБОТЫ ТЯГОВЫХ ЭЛЕКТРИЧЕСКИХ ДВИГАТЕЛЕЙ ПОСТОЯННОГО ТОКА

A MATHEMATICAL MODELING OF AC ELECTRIC LOCOMOTIVE WITH ACTIVE CONVERTER IN TRACTION

One of the ways to increase the power factor of AC electric locomotives with DC traction motors is the use of converters on fully controlled semiconductor devices — active current source rectifiers. However, the modes of operation of the active current source rectifier as a DC voltage regulator have not been studied enough today and require further investigation. In this article, a mathematical model of an AC electric locomotive with an active traction converter (based on the eight-axle freight AC locomotive 2EL5) with two-zone regulation of the DC voltage is developed. The model of the “traction network — electric locomotive” system is presented in the form of differential equations. The algorithm of the active converter control system is described by logical switching functions. The converter uses a unipolar rectangular-stepped pulse width modulation with a carrier frequency of 1200 Hz. Computer modeling of electromagnetic processes in the traction mode is performed. The oscillograms of voltages and currents show the process of transition from the first control zone to the second one. According to experiments, the power factor of an electric locomotive in the entire control range is 0.83...0.99. This is more than a thyristor converter. The THDi of the trolley wire current is about 9...10%. Analysis of the trolley wire voltage and current waveforms showed that a decrease in the modulation index has a negative effect on the voltage and current harmonic distortion. Further research should focus on limiting the higher harmonics of voltage and current when adjusting the voltage. The practical result of the use of active traction converters on electric locomotives is a reduction in the consumption of electric power for the traction of trains.

Inter‐turn short‐circuit assessment of DC motor used in railway locomotive

This study deals with inter-turn short-circuit assessment of DC traction motors used in railway locomotives. This has been done by analysing input current spectra of rectifier unit feeding the traction motor. The analysis includes multi-resolution analysis and discrete wavelet transform (DWT) of current spectra to calculate approximate and detailed coefficients and then to evaluate the skewness, kurtosis and root mean square values. Variation of those values with respect to percentage of inter-turn short circuit at different DWT decomposition levels has been observed. A number of curves have been chosen for fault assessment based on the observations. Deviations from normal condition have also been observed by logic matrix. Depending on the features obtained, normal and different percentages of short in the traction motor windings have been classified and an algorithm has been proposed accordingly. Case study has been carried out on Indian WAP4 locomotive, wherein the input current to the rectifiers has been analysed and efficacy of the proposed algorithm has been validated. If for the locomotives, these parameters are monitored, percentage of inter-turn short circuit in the winding may be assessed far before massive system degradation occurs.

Активний тяговий перетворювач з широтно-імпульсною модуляцією для електровоза змінного струму з колекторними тяговими двигунами

One way to increase the energy efficiency of AC electric locomotives with DC traction motors is to use converters on fully controlled semiconductor devices. Power circuit and control algorithm of active traction converter with two-zone voltage regulation are developed in this article. As an algorithm for controlling IGBT-transistors, rectangular-stepped pulse width modulation with a carrier frequency of 1200 Hz is used. The simulation of the active traction converter is performed in MATLAB. The results of the experiments showed that the power factor of 2EL5 electric locomotive with a new converter is 0.83...0.99 over the entire range of loads. This is more than for a thyristor rectifier. The THDi of the contact wire current is up to 13%. In further research, we must focus on finding ways to compensate for the higher harmonics of the voltage and current of an electric locomotive under PWM voltage regulation.

Аnalysis of operating modes of single­phase current­source rectifier with rectangular­stepped pulse­width modulation

The operating modes of the single-phase active current-source rectifier in the case of rectangular-stepped pulse-width modulation and load in the form of DC traction motor are investigated. The single-phase bridge rectifier circuit with a discharge diode is considered. The mathematical model of the rectifier is developed and the main ratios for pulse-width modulation with rectangular-stepped modulating signal are determined. On the computer model, electromagnetic processes at three modulation frequencies (900, 1,200, 1,800 Hz) are studied. The features of the effect of the modulation depth and frequency on the rectifier power factor and the total harmonic voltage and current distortion in the mains supply are determined. The DC motor for today remains the main type of the traction motor of the 25 kV, 50 Hz AC mainline electric locomotives of alternating current in Ukraine and in some other countries. To power such motors, diode or thyristor rectifiers are used. At the same time, it is known that converters on fully controlled semiconductor devices provide higher power efficiency. The studies allow determining what values of modulation frequency and depth provide a high power factor (more than 0.9) and minimum total harmonic voltage and current distortion distortions in the mains supply. This allows finding rational approaches to the selection of power circuits and control algorithms for active converters in the traction electric drive of electric locomotives. The efficiency of increasing the power factor and reducing the total harmonic voltage and current distortion can be achieved, first of all, by reducing the power consumption for traction of trains. According to the set of selected comparison criteria, the active current-source rectifier with a modulation frequency of 1,200 Hz is the most suitable for implementation in the traction electric drive of the electric locomotive. Provision of high power characteristics in a wide range of traction loads can be achieved in the multi-zone circuit of such a converter.

Traction induction motor

The paper presents a traction induction motor with an innovative rotor winding design. The winding of the rotor is almost identical to the armature winding in the dc traction motors, with the exception of commutator. Winding is double layered. The bars are insulated. Along the iron core bars are secured with wedges and in the winding outhang with bandages. The bars of the bottom layer in the winding outhang part near the iron core are bent radially in the direction of the shaft axis. On the winding outhang of the bottom layer an inner bandage is applied. On the winding outhang of the top layer an outer bandage is applied. All the ends of the bottom and top layers bars, on both sides of the rotor’s core, are connected together by ferrule. There is a ring placed on the shaft or on the coil support on one side of the rotor’s core. It is best if this ring is made of copper. The ring is characterized by mp tongues, which are distributed evenly along its circumference (p is number of winding pole pairs and m is number of rotor winding phases). Tongues are connected to equally uniformly placed ferrules. Bandages are made of carbon fibre or glass fibre tape.

Electromagnetic processes of charging of on-board supercapacitor storage system during the regenerative braking mode of DC electric rolling stock with series-wound DC motors

The paper is dedicated to the task of improving of regenerative braking of a DC train with the series-wound DC traction motors. It is proposed the schematic solution for the trains with DC motors, which is based on the storing of recovered energy by the on-board supercapacitor storage system and extending the speed range of regenerative braking. The scheme is described by expressions which allowed to build the time dependences of main values. In addition, the experimental researches with the multiple-unit train were performed to find initial data for calculations and verification the results. The transient processes of charging are analyses for different cases of storage capacitances, residual voltages and initial speed of braking. It was proved, that the scheme allows to increase the value of recovered energy up to 40%, but its value strongly depends on the initial conditions and parameters of the system.

IOT based control of DC traction motor

IOT based control of DC traction motor

A METHOD FOR TRAIN WEIGHT ESTIMATION

[For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version)].ABSTRACT There are difficulties and deficiencies in procedures of weighing of railway cars and trains, as well as there is a persisting need to know cargo loads on the rail track. The article offers a simple way to estimate weight of a train as it moves along a control track section. It is based on measurement of intensity of magnetic field generated by locomotive DC traction motors. The role of weighing devices is performed by ferroprobes having as recording devices milliammeters with a calibrated scale for measuring train weight. The results achieved by the authors confirm method’s effectiveness. Keywords: train weight, locomotive, DC traction motors, constant magnetic field, magnetic field intensity, ferroprobes, train weighing method.

Power quality analysis in electric traction system with three-phase induction motors

Three-phase induction motors are widely used in electric traction systems. The impacts of the traction vehicles equipped with three-phase induction motors on power quality are much different from the impacts of vehicles with DC traction motors. In this paper, the effects of the traction vehicle operation with three-phase induction motors on power quality in a 110kV transmission network are investigated.The electric traction system 25kV, 50Hz and the traction vehicle with three-phase induction motors were modeled including AC/DC rectifier and DC/AC inverter based on IGBT technology. The parameters of those power electronic elements directly determine the current and voltage waveforms, and consequently power quality parameters.Measurements and calculations of power quality parameters were presented. Three operation modes of traction vehicle were considered including acceleration, constant drive and regenerative breaking. During the test drives, the values of total harmonic distortion, unbalance, flicker and power factor were obtained.