Main Traction Research Articles

Efficiency Enhancement of Traction System Based on Loss Models and Golden Section Search in Electric Vehicle

Abstract Due to the main traction force of electric vehicles (EVs), the overall efficiency of inverter-motor in traction system can seriously affect the energy consumption of EVs. In this paper, a novel hybrid methodology based on loss model and golden section search is proposed. Firstly, the iron loss, copper loss and stray loss of motor, combined with conduction loss and switching loss of inverter, are modeling. And the models of losses are validated by an experiment. Secondly, two efficiency improvement methodologies are investigated, namely loss model strategy and gold section search strategy. Then, a hybrid efficiency optimization control strategy is proposed based on losses model of the inverter-motor system and the two conventional methods, which yields a high efficiency operation point of inverter-motor system during different loads. Additionally, such novel methodology manifests faster search speed and more search accuracy than the conventional methods. Finally, an experiment results validates the effectiveness of the proposed hybrid control strategy.

Modular Concept of Auxiliary Converters for Diesel Electric Locomotives

Nowadays almost every modern diesel electric locomotive includes auxiliary converters. Auxiliary converters and drives are an integral part of the main traction drives. Auxiliary converters provides cooling of main drives, traction motors, diesel engine, charging the vehicle's batteries and feeding of control circuits in entire locomotive. Auxiliary converters for diesel electric locomotives consists of inverters, chargers, alternator exciters and DC/DC converters of different voltage levels. Due the fact of the equal working principles of individual converters groups, certain amount of power classes has been designed and developed. Also for these groups of converters has been developed universal parameterized control software. The main advantage of parameterization and power classes for individual converters groups is simple design. This feature simply allows to build up complete auxiliary converter for a specific customer application. It is also possible to design and integrate smart converters, which automatically set correct required parameters in locomotive immediately after connecting.

Industrial frequency single-phase AC traction power supply system for urban rail transit and its key technologies

To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail transit. The proposed system consists of a main substation (MSS) and cable traction network (CTN). The MSS includes a single-phase main traction transformer and a negative-sequence compensation device, while the CTN includes double-core cables, traction transformers, overhead catenary system, rails, etc. Several key techniques for the proposed system were put forward and discussed, which can be summarized as (1) the power supply principle, equivalent circuit and transmission ability of the CTN, the cable-catenary matching technique, and the selection of catenary voltage level; (2) the segmentation technology and status identification method for traction power supply network, distributed and centralized protection schemes, etc.; (3) a power supply scheme for single-line MSS and a power supply scheme of MSS shared by two or more lines. The proposed industrial frequency single-phase AC traction power supply system shows an excellent technical performance, good economy, and high reliability, hence provides a new alternative for metro and urban rail transit power supply systems.

Software for calculation of belt conveyors at their computer-aided design

The article is devoted to developing algorithms and software for automated calculation of the main traction characteristics of the conveyor for the second option, involves designing the conveyor for installation in a particular formulation, when given the receiving capacity, operating performance, circuit tracks, production type, method of installation of the load it is determined velocity, width, type and strength of the belt, power and traction drive factor, tensioner stroke, drive starting time, force of the braking device and size of the assembly units. The basis is known calculation method. There are considered various options of the conveyor – single and double-drum, with the presence of the clamping roller or belt, with rigid kinematic coupling or connection between independent drums. It is formalized the second stage of the problem of computer-aided design of mine conveyors, using known methods approved by the State Standard. It is developed visual form to the user interface based on the example of the basic parameters of mine conveyor which is established in the programming language Delphi 7. To automate the calculation of these parameters is used programming language. The visual forms of the calculating algorithm realization of traction capacity of the conveyor drive are given.

Active Disturbance Rejection Controller Design for Electric Vehicle Traction System

In some low velocity electric vehicle system, Brushless DC motor is used for the main traction motor. However, the low-velocity stability should be guaranteed, especially with the suddenly-changing load, the velocity response should be more quick and the overshoot should be small, all of above can make the vehicle more comfortable. The traction system is controlled by a current loop and a velocity loop, so a new method is proposed, that PI control strategy is in the current loop and the active disturbance rejection controller is in the velocity loop to restrain the bad effect results from suddenly-changing load. This active disturbance rejection controller is composed of a tracking differentiator, an extended state observer, a nonlinear state error feedback controller, and etc. The parameters of the controller are optimally designed, and the simulation results show that this control strategy can effectively restrain the suddenly-changing load and improve the vehicle’s low velocity performance.

External magnetic field density of main traction transformer for EMU

PurposeThe purpose of this paper is to determine the external magnetic field density of the traction transformer for EMU and to find the model for its computation.Design/methodology/approachThe magnetic flux density in the surrounding region of the traction transformer was modeled and calculated using FEM. The transformer was modeled in a way that tank, clamps and current sources were taken into account. Most frequent operating modes for the basic 50 Hz current harmonic, and most represented higher harmonic of 1,950 Hz loading current, were analyzed.FindingsMatching calculated and measured values were obtained on the finished transformer. The developed calculation has proved to be a useful tool for the stray field calculation outside this type of transformer. Calculated values of the flux density are lower then the maximum permitted values defined by the DIN VDE 0848 standard.Originality/valueThis paper presents a study of calculation compared to measurement of magnetic field density outside an oil immersed transformer.

New Configuration of Traction Converter With Medium-Frequency Transformer Using Matrix Converters

This paper presents a new configuration of a main traction converter with a medium-frequency transformer (MFT) using matrix converters intended for locomotives and particularly for suburban units supplied by a 25-kV/50-Hz and/or 15-kV/16.7-Hz ac electrification system. Single-phase matrix converters are employed in the primary medium-voltage converter which is directly connected to the ac trolley line. The output of the primary ac/ac converter supplies the primary side of the MFT. The proposed MFT-based topology of the traction converter replaces the bulky main line transformer found on board railway vehicles. Particularly in countries with a catenary of 15 kV/16.7 Hz, very low catenary frequency results in huge and heavy traction transformers. The developed topology is a power electronics solution that considerably reduces weight and losses in a traction propulsion system. The proposed converter configuration with cascaded matrix converters on the primary side of the MFT presents a new research direction in the field of traction converters with MFTs. This paper describes in detail the proposed power circuit and the control of the traction converter. The behavior of the traction converter configuration has been analyzed using simulations and experimental tests carried out on a developed low-voltage laboratory prototype of a traction converter with a rated power of 4 kVA. Based on extensive simulation and experimental study, this paper reviews the benefits, drawbacks, and constraints of the developed traction converter configuration.

Vector Control System of Permanent Magnet Brushless Motor Based on Discrete Position Signals

Permanent magnet brushless motor (PMBM) has been one of the main traction motors used in electric vehicle (EV).A vector control method with low cost and high performance is presented to meet the requirement of EV,such as high torque at low speed,wide adjustable speed range with constant output power at high speed.The method takes vector control of PMBM with discrete position signals at EV start and at low speed,and with continuous position signals at high speed.Without increasing the cost of PMBM and its control system,this method gets rid of the disadvantage of narrow field-weakening speed range for PMBM at high speed,and upgrades the performance of PMBM in the whole speed range.

Application of Speed and Load Torque Observers in High-Speed Train Drive for Diagnostic Purposes

In this paper, an application of speed and load torque observers is presented. The aim of the observer implementation is to be used in the diagnostic system for a motor speed sensor and a torque transmission system. The diagnostic system is dedicated to the high-speed train propelled by an induction motor. An analysis of the observed variables allows the identification of problems in the mechanical part of the main traction drive. For example, in the case of speed sensor faults, the motor control system could be switched into speed-sensorless control. The proposed observers were verified by simulation and on a test bench for 1.2-MW rail vehicle motor used in high-speed trains.

High-Performance Control of Two Three-Phase Permanent-Magnet Synchronous Machines in an Integrated Drive for Automotive Applications

The closed-loop control of an integrated dual AC drive system is presented to control two three-phase permanent-magnet motors. A five-leg inverter is employed in the drive system; three of the inverter legs are for a main traction motor, but only two are needed for a three-phase auxiliary motor by utilizing the neutral point of the traction motor. An integrated drive with reduced component count is therefore achieved by eliminating one inverter leg and its gate drivers. A modified current control scheme based on the rotor flux orientation principle is presented. Simulation and experimental results are included to verify the independent control capability of the integrated drive.

A New Sensorless Drive Control System for Transmissionless EVs Using a Permanent-Magnet Synchronous Motor

One of the most important technologies for electric vehicles (EVs) will be drive control technology for main traction motors. It is desired for the drive control system to have the following characteristics: 1) it is based on vector control methods that allow quick, efficient and/or precise torque production; 2) it can produce 150-250% rated torque at standstill and can have wide driving-range, consequently can allow development of EVs with no variable-transmission; 3) it does not require a position/speed sensor for controlling motor drive, which has been mounted on a rotor shaft. This paper proposes a new sensorless drive control system for such EVs using a permanent-magnet synchronous motor as a main traction motor. Potential usefulness of the proposed drive control system is examined through the development of a prototype EV capable of driving on public road.

Diesel Locomotive Retrofit: Conceptual Design with Twin Turbines Reduces Overall Emissions

The fine particulate matter component of diesel engine exhaust has been declared by the state of California to be a human carcinogen at any concentration and is therefore subject to measures for its reduction or total elimination. The diesel locomotive contribution to this problem is projected to be 46% of the total particulate tonnage from diesel engines in California in 2010. A conceptual design substitutes gas turbines for the main traction engine and head-end power (HEP) engine of a typical diesel electric commuter locomotive. Retaining the existing HEP engine while replacing the traction engine also is evaluated. Relying on burning conventional diesel No. 2 fuel oil, the conceptual design is projected to significantly reduce or eliminate measurable particulate matter and significantly reduce other exhaust pollutants. Because the gas turbine readily adapts to natural gas as a fuel without any loss in performance, the economics and additional emissions benefits also will be developed for the use of liquefied natural gas.

Stability Analysis of Permanent Magnet Synchronous Motor Traction Main Circuit with Regenerative Braking on Insufficient Load's Power Consuming

The regenerative braking method has been employed in DC-fed electric railway vehicle traction system in order to reduce energy consumption. The load's power consuming is sometimes insufficient for the regenerated power, and it causes the input voltage of traction inverter rises. In such a case, the regenerative current is regulated to prevent the over voltage. However, in applying this regulation, especially to the permanent magnet synchronous motors (PMSM) traction system, a continuous oscillation of regenerative current is sometimes observed. Unfortunately, It deteriorates passengers' riding comfortability due to torque fluctuation.On this paper, we analyze the phenomena of the oscillation of regenerative currents and suggest an anti-oscillation regenerative current regulation method based on the analyzing results. The detail is as follows.(1) We construct a nonlinear time-varying model, which consists of the substation, power feeding system and the main traction circuit onboard and divide the nonlinear time-varying model into four linear time-invariant systems.(2) Through the analysis with the models, we make it clear that the continuous oscillation is caused by the traditional regenerative braking control method(3) Based on the analysis we suggest a novel anti-oscillation regenerative braking control method, whose effectiveness is proved through experiments.

Vehicle Traction Performance on Snowy and Icy Surfaces

Snow and ice have been considered the main factors that contribute to reduced vehicle traction forces and potential traffic accidents during winter. To increase a vehicle's traction on snow and icy surfaces, studded and nonstudded winter tires have been used in cold regions. However, the use of studded tires causes significant pavement damage, such as accelerated pavement rutting and pavement marking damage. Since spring 1994, the Alaska Department of Transportation and Public Facilities has asked the Transportation Research Center at the University of Alaska Fairbanks to conduct a series of research studies related to vehicle traction performance on snow and icy surfaces in Alaska. One of the studies conducted in 1995 is summarized. The main objectives of the study were to evaluate (a) traction performance of used winter tires on roadways, (b) traction performance comparison of lightweight studded tires with other winter tires, (c) traction performance of vehicles with two front studded tires, and (d) effects of vehicle type on traction performance. Field tests were conducted on traveled roadways and in parking lots. The main traction performance measurements included stopping distances, maximum stopping deceleration forces, time necessary to reach a certain speed, and maximum starting acceleration forces.

Non-Newtonian and Thermal Effects on Film Generation and Traction Reduction in EHL Line Contact Conjunctions

The thermal circular non-Newtonian model accompanied with three specialized models was used to study the mechanisms of film generation and traction reduction in EHL line contact conjunctions. Results revealed that the film generation capability is mainly controlled by the inlet zone pressure buildup and the inlet zone piezo-thickening. The diffusion time effect enhances the thermal thinning that reduces this capability. On the other hand, the piezoviscosity and the shear rate in the central contact zone are the main traction generation factors whereas shear skidding and thermal skidding are the traction reduction mechanisms. Results also showed that neglecting either viscous heating or the combination of shear thinning and shear stress reduction in formulating an EHL simulator is inaccurate for many cases.

Unbalanced Current in Split Brushes

Main traction motors MT 200 for the New Tokaido Line, which are used at high speed and high current density in pulslating or direct current, are carefully designed in order to keep good commutation and the brushes used are split ones made from soot. As tempered colour was considerably noticed at the pig tails of brushes in the car running test, unbalanced current among brushes was measured in the original machine with the voltage drop method at stand test of factories.Obtained results are followed;(1) Unbalanced current between brush splits is higher at the leading split than at the trailing one, and indicates considerably larger value than the general unbalanced current among parallel brushes. This causes are assumed mainly to be the motor design constructed of over-commutation.(2) Though sliding charactristics of split brushes depend upon each split moving independently, this independency causes unbalnced current.(3) Since the unbalanced current in split brushes is unavoidable, selection of brush current density and fastening method of brush pig tails should be designed move carefully.

Test of Carbon Brush by Impact Tester and its Relation to General Characteristics

The impact tester is available for determination of resistance to impact failure of carbon brush for main traction motor on the electromotive car.The present standard practice of test using this means is, as reported earlier, conducted by gradually varying the rotation number of slip ring and changing accordingly the rotation number of brush load alternately. Hereby, the impact resistance of brush is indicated in terms of the time until two of the sixpieces of test specimens develop the failure area exceeding 10 % of total area of contact.Assuming that the failure of brush is proportional to the impact it suffers, it will be approximately proportional to the product of brush pressure (load) and slip ring velocity (impact number).However, in the conventional test proedure, rotation number as well as brush pressure is varied that is, three variables-load W, rotation number S and state of failed surface-are involved. Hence, comprison of time to failure will not indicate the relative resistance of brush. This means that brush of 60 hr. resistance will not be two times as endurable as one of 30 hr. resistance.The Authors carried out the test with a different approach. Under the constant condition of load, 500 gr/cm2 and slip ring rotation, 1000 R. P. M., comparisons were made in terms of failure extent and time to failure.For this purpose, the extent was roughly classified into small, moderate and great. Each class, then, was represented by a median; thus the failue extent was weighted as well as time to failure. According to this method, both failure extent and time to failure are taken into account, so it will be convenient in comparing the relative merits of brushes and in correlating the failure extent of brushes in service and test data by the impact tester.If the test data by the impact tester are checked in relation to brush properties by simple correlative analysis, it will be seen that according to this system of indication there is no correlation existing item for item; only in point of tensile strength or combined characteristics, some relation can be disclosed.

Auxiliaries for High-Voltage D-C. Multiple Unit Cars

The selection and application of auxiliary electrical devices on a high-voltage multiple unit car is of almost as much importance as the application of the main traction apparatus and requires careful consideration. This paper contains a description of the engineering features as worked out for electrified suburban lines operating on 1500-volt and 3000-volt systems. The control circuits have become very generally standardized at 32-volts, which is also well adapted for interior illumination and headlights. A motor driven generator supplies 3-to 5-kw. power per unit for control lights and battery charging. Such devices as heaters and motor-generator sets, requiring a considerable amount of electrical power, are necessarily constructed to operate at trolley potential. On the 1500-volt system, the compressor can be operated directly from the line potential while on the 8000-volt systems, a double commutator motor driving the generator supplies a 1500-volt source of power for the compressor.

Auxiliaries for high-voltage D-C. multiple unit cars

The selection and application of auxiliary electrical devices on a high-voltage multiple unit car is of almost as much importance as the application of the main traction apparatus and requires careful consideration. This paper contains a description of the engineering features as worked out for electrified suburban lines operating on 1500-volt and 3000-volt systems. The control circuits have become very generally standardized at 32-volts, which is also well adapted for interior illumination and headlights. A motor driven generator supplies 3-to 5-kw. power per unit for control lights and battery charging. Such devices as heaters and motor-generator sets, requiring a considerable amount of electrical power, are necessarily constructed to operate at trolley potential. On the 1500-volt system, the compressor can be operated directly from the line potential while on the 8000-volt systems, a double commutator motor driving the generator supplies a 1500-volt source of power for the compressor.