Volume 11 INSTRUCTION MANUAL EXERCISING THE AC DRIVE PROPULSION MODEL

Transcription

1 Volume 11 INSTRUCTION MANUAL EXERCISING THE AC DRIVE PROPULSION MODEL Richard A. Uher RAIL SYSTEMS CENTER 2013 Country Club Drive Mount Vernon, PA TOM Version 3.4 Edition October 15, 2012

2 Preface This document is part of a series of instruction manuals, which can be used as guidelines for applying the Train Operations Model (TOM) to rail systems throughout the world. In this connotation, rail system definition includes main line railroads, heavy and light rail, trolleybuses, high-speed rail and MAGLEV and people movers. There are several manuals in the series: Volume 1 An Introduction to the Instruction Manual for Applying the TOM Volume 2 Instruction Manual for Applying the TOM to Transit Systems DC Electric English Units Volume 3 Instruction Manual for Applying the TOM to Transit Systems DC Electric Metric Units Volume 4 Instruction Manual for Applying the TOM to Transit Systems AC Electric English Units Volume 5 Instruction Manual for Applying the TOM to Transit Systems AC Electric Metric Units Volume 6 Instruction Manual for Applying the TOM to Railroads Fueled English Units Volume 7 Instruction Manual for Applying the TOM to Railroads Fueled Metric Units Volume 8 Instruction Manual for Applying the TOM to Rail Systems; Technology Aspects Volume 9 Instruction Manual for Procedures and Shortcuts in the TOM Volume 10 Instruction Manual for Including the Return Circuit in Electric Rail Systems Volume 11 - Instruction Manual Exercising the AC Drive Model Volume 12 Instruction Manual DC Electric Power System Methodology Volume 13 Instruction Manual AC Electric Power System Methodology Volumes 2-7 cover nearly all transit systems and railroads in the world. This instruction manual is Volume 11. These volumes are unprotected. Thus the user is free to make notes or rewrite sections according to his preferences. The primary purpose for using the TOM is evaluation. The evaluation generally takes the form of a study, with certain objectives, which may or may not be well defined. As the study is conducted, new objectives may result, because of unanticipated results. Within the framework of evaluation, designs may be modified and further evaluated, so that in this sense, the TOM may be considered a design tool. The TOM is used together with other standard software, such as Microsoft Office (in particular, WORD, EXCEL and POWERPOINT). This combined package is most effective in assembling client data as well as presenting results. In some instances, the TOM interacts directly with these office programs, while in other cases; the user handles the office packages directly. 2

3 Table of Contents 1 INTRODUCTION PARAMETER VARIATION - BASE CASE BASE CASE MODEL FILES BASE CASE TRAIN FILE Train File Screens Traction Curves PARAMETER VARIATION - ACTUAL MOTOR PARAMETERS Stator Resistance (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Stator Inductance (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Core Inductance (Variance = ±20%) Traction Effort Curves Traction Efficiency Curves Core Resistance (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Rotor Inductance (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Rotor Resistance (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Frequency at Maximum Voltage (Variance = ±20%) Traction Effort Curves Traction Efficiency Curves Maximum Stator Current (Variance = ±20%) Traction Effort Curves Traction Efficiency Curves Number of Pole Pairs (Variance = ±1) Traction Effort Curves Traction Efficiency Curves Friction Losses Coefficient 1 (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Friction Losses Coefficient 2 (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Windage Losses (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Stray Losses (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Motor Parameter Variation Analysis Gear Ratio (Variance = ±20%) Traction Effort Curves Traction Efficiency Curves Wheel Diameter Motor Parameter Analysis CONTROL PARAMETERS Line Reactor Resistance (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Main Device Forward Drop (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Motor Reactor Resistance (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Maximum DC Current Modulation Frequency Filter Capacitor Resistance (Variance = ±50%)

4 Traction Effort Curves Traction Efficiency Curves Free Wheeling Diode Forward Drop (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Constant Losses (Variance = +1) Traction Effort Curves Traction Efficiency Curves Control Parameter Variation Analysis GEAR UNIT PARAMETERS No Gear Losses Traction Effort Curves Traction Efficiency Curves Constant Power Term (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Constant Torque Term (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Torque Term (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Speed Term (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Speed Squared Term (Variance = ±50%) Traction Effort Curves Traction Efficiency Curves Gear Unit Parameter Variation Analysis VOLTAGE VARIATION INTRODUCTION CONSTANT VOLTAGE CURVES Traction Effort Curves Traction Efficiency Curves VOLTAGE VARIATION WITH POWER Variable Voltage Case 1 (Max 850 Nom 700 Min 450) Traction Effort Curves Traction Efficiency Curves Variable Voltage Case 2 (Max 850 Nom 650 Min 450) Traction Effort Curves Traction Efficiency Curves Variable Voltage Case 3 (Max 750 Nom 700 Min 450) Traction Effort Curves Traction Efficiency Curves Variable Voltage Case 4 (Max 750 Nom 650 Min 450) Traction Effort Curves Traction Efficiency Curves VOLTAGE VARIATION PERFORMANCE AC DRIVE TEST TRACK TPS INPUT FILES Control File Train Files Station Files Grade and Curve Files Speed Restriction File Route File File of Filenames Files ENS INPUT FILES Network File Operating Time File Train Location File Current Measurement Input Files Power Profiles ENS File of Filenames Files TPS RESULTS Run Times Energy of Run PEAK POWER AND MINIMUM VOLTAGE SELECTION OF A VOLTAGE VARIATION SCENARIO

5 5.6.1 Voltage Variation Scenario 2x20 Efficiency Matrix Voltage Variation Scenario 20x20 Efficiency Matrix Performance Characteristics Train Performance Simulation Results Electric Network Simulation Results DESIGN OF AC DRIVE FOR THE COMPUTER LAB OF THE TOM TRAINING COURSE INTRODUCTION BASE CAR CAM CONTROL MODEL NAME CONVENTION TRACTION CURVE MATCHING EFFICIENCY RUNS WITHOUT REGENERATION FINAL DESIGN

6 1 INTRODUCTION The AC Drive is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage. Modern rail systems are becoming more and more dependent on the AC Drive as the propulsion system of choice because of its lower initial and operating cost. AC Drives for modern traction consist of a variable frequency and variable voltage solid state control of three phase ac induction motors. Most of the modern traction systems which are now produced for rail cars, even on older rail systems, are AC Drives. The Train Operations Model (TOM ) has built into it an AC Drive SubModel, which can be used to provide the electrical characteristics of the AC Drive propulsion system, which are further used to simulate train and power system operation. The purpose of this study is to apply that SubModel in order to study parameter sensitivity and other electrical characteristics. In particular, it would be important to know which parameters have the greatest effect on the Traction Effort and Traction Efficiency Curves, in order to determine motor design parameters, which manufacturers are reluctant to give to clients which use the TOM. A description of the AC Drive model used in the TOM is provided in the TOM Program Manual. Chapter 2 defines the base case for the AC Drive study. The base case is the AC Drive to which all other AC Drives are compared. A change in one of the parameters of an AC Drive produces a new AC Drive to be compared to the original. Chapter 3 contains a discussion of the sensitivity of AC Drives to the parameters which define them. This discussion is presented in terms of the parameter change on the Traction Effort and Traction Efficiency. Sensitivity is put into quantitative terms. For variation of one of the parameters of the motor, inverter and gear unit models by a fixed percentage in the positive and negative directions, traction effort curves (tractive effort and electrical braking effort) and traction efficiency curves are presented and compared to the base case. Chapters 4 and 5 view the AC Drive from the point of view of input line voltage variation. The line voltage varies as a result of the current being drawn by the train as well as the currents being drawn by all of the other trains on the power system feeding the trains. Most models used in power systems studies do not take this into account. It is important to know how much capability the AC Drive has relative to its performance requirements. Maximum voltage drops and performance are usually obtained by assuming a constant voltage for the train, which can range from open circuit voltage to minimum voltage allowed on the line. If a power system is designed on this basis, it can be either designed conservatively or liberally depending on the selection of this voltage. A conservative design will use a nominal train voltage close to the open circuit voltage, while a liberal design will choose the nominal voltage, which is lower. Choice of this voltage will also determine the schedule performance and energy consumption of the train. The TOM has the capability of developing traction and efficiency curves where the line voltage varies with the power drawn. Chapter 4 considers development of power dependent curves, while chapter 5 evaluates performance on the basis of these curves. An iteration process for determining both nominal and minimum voltages is outlined for use with the TOM. This is a less conservative approach to power system evaluation. The TOM Training Course, which is offered to any licensee of the TOM, provides an exercise to develop and AC Drive using the propulsion system SubModel of the TOM. 6

7 These trains are replacing trains which use an old style resistor control propulsion model and there is a requirement that they have the same performance as the older style trains. Chapter 6 illustrates how this process is conducted. 7

8 2 PARAMETER VARIATION - BASE CASE 2.1 BASE CASE MODEL FILES The base case chosen for the motor is ACDR.mot and the Inverter is ACDR.con. The gear unit model is ACDR.gum. The screens are: 8

9 The equivalent circuit is shown next. The PWM Inverter and Gear Unit are shown next. 9

10 These represent the base case for the AC Drive. All variations of parameters will be referred to this base. 10

11 2.2 BASE CASE TRAIN FILE Train File Screens The Base Case Train file was built using these parameters. The File Construction Module Train File Input Main Screen is shown next. The File Construction Module Train File Input Train Makeup Input screen is shown next. 11

12 The File Construction Module Train File Input Propulsion Input screen is shown next. The File Construction Module Train File Input Electric Propulsion Model Input screen is shown next. 12

13 The Base Case Train file is named T-AC00.acd Traction Curves 13

14 The Traction Effort Curves produced by the Base Case Train file T-AC00.acd are shown next. The efficiency curves are shown next. 14

15 Only one curve is shown for both power and electrical braking. This results from selecting a 2x20 efficiency matrix for the train file. It is this assumption that most studies use. This assumption will be checked later by using a 20x20 efficiency matrix. 15

16 3 PARAMETER VARIATION - ACTUAL 3.1 MOTOR PARAMETERS The following motor parameters will be varied for the AC Induction Motor. 1. Stator Resistance 2. Stator Inductance 3. Core Inductance 4. Core Resistance 5. Rotor Inductance 6. Rotor Resistance 7. Maximum Motor Speed 8. Frequency at Maximum Voltage 9. Maximum Stator Current 10. Number of Pole Pairs 11. Friction Loss Coefficient Friction Loss - Coefficient Windage Loss 14. Stray Loss The effect of these variances on the Traction Curves will be displayed. In addition to the specified motor design parameters, the motors drive the wheels and two important additional parameters are the wheel diameter (D) and the gear ratio (GR). These two parameters are necessary in order to convert motor rotary speed (RPM) to train speed (v) and motor torque (τ) to traction effort (TE) [either tractive effort or electrical braking effort]. The formulae are: v = k1*rpm*d/gr and TE=k2*N*GR*τ/D. Where N is the number of motors and k1 and k2 are constants whose value depend on whether the units chosen are English or Metric. Note that the ratio (D/GR) appears in both formulae, so that an increase in the gear ratio can be compensated for by a decrease in the wheel diameter. 16

17 3.1.1 Stator Resistance (Variance = ±50%) Traction Effort Curves 17

18 Traction Efficiency Curves 18

19 3.1.2 Stator Inductance (Variance = ±50%) Traction Effort Curves 19

20 Traction Efficiency Curves 20

21 3.1.3 Core Inductance (Variance = ±20%) Traction Effort Curves 21

22 Traction Efficiency Curves 22

23 3.1.4 Core Resistance (Variance = ±50%) Traction Effort Curves There are no differences in the Traction Effort Curves Traction Efficiency Curves 23

24 3.1.5 Rotor Inductance (Variance = ±50%) Traction Effort Curves 24

25 Traction Efficiency Curves 25

26 3.1.6 Rotor Resistance (Variance = ±50%) Traction Effort Curves 26

27 Traction Efficiency Curves 27

28 3.1.7 Frequency at Maximum Voltage (Variance = ±20%) Traction Effort Curves 28

29 Traction Efficiency Curves 29

30 3.1.8 Maximum Stator Current (Variance = ±20%) Traction Effort Curves 30

31 Traction Efficiency Curves 31

32 3.1.9 Number of Pole Pairs (Variance = ±1) Traction Effort Curves 32

33 Traction Efficiency Curves 33

34 Friction Losses Coefficient 1 (Variance = ±50%) Traction Effort Curves 34

35 Traction Efficiency Curves Extremely small differences, which are less than in efficiency. 35

36 Friction Losses Coefficient 2 (Variance = ±50%) Traction Effort Curves 36

37 Traction Efficiency Curves Extremely small differences, which are less than in efficiency. 37

38 Windage Losses (Variance = ±50%) Traction Effort Curves 38

39 Traction Efficiency Curves 39

40 Stray Losses (Variance = ±50%) Traction Effort Curves No difference in the traction curves Traction Efficiency Curves 40

41 Motor Parameter Variation Analysis The conclusions reached here relate to the Traction Effort and Efficiency Curves, which have been presented in previous sections. These relate to conditions for selecting an AC Drive for a particular transit job. Some parameters of a motor selection are not within the prerogative of the motor designer. Others are, and as such, can determine the application. Thus, if a supplier provides the Traction Curves and other physical parameters such as wheel diameter and gear ratio, a good estimate can be made of the Efficiency Curves, using the internal AC Drive SubModel of the TOM. The first six parameters to be considered are the electrical impedances of the Stator, Core and Rotor. Both inductance and resistance are considered. 1. Stator Inductance. The variation is ±50%. The traction effort curves show a small variation with the changes and the same direction. Increased inductance implies a slightly larger traction effort while decreased inductance implies a smaller tractive effort. The efficiency curves are more complicated especially below 25 mph. For speeds higher than 25 mph, there are very small differences where higher efficiency is obtained with reduced stator inductance and visa versa. 2. Stator Resistance. The variation is ±50%. The traction effort curves show a very small variation with the changes and the same direction. Increased resistance implies a slightly larger traction effort while decreased resistance implies a smaller tractive effort. The power efficiency curve is rather smooth, showing a small increase in efficiency with decreased stator resistance and a small decrease in efficiency with increased stator resistance. The braking efficiency curve is more complicated for speeds below 20 mph but above 20 mph follows the same trend as the power efficiency curve. 3. Core Inductance. The variation is ±20%. The traction effort curves show a substantial variation with the changes and the same direction. Increased inductance implies a larger traction effort while decreased inductance implies a smaller tractive effort. The variations become smaller with increasing speed and vanish completely at the top speed. The power efficiency curve is rather smooth, showing a small increase in efficiency with decreased stator resistance and a small decrease in efficiency with increased stator resistance. The braking efficiency curve is more complicated for speeds below 20 mph but above 20 mph follows the same trend as the power efficiency curve. 4. Core Resistance. The variation is ±50%. The traction effort curves show almost imperceptible changes. Increase in resistance produces a slightly weaker curve (TE and EBE are lower for the same speed) while a decrease in resistance results in a stronger curve (TE and EBE are higher for the same speed). The variation in the efficiency curves are also imperceptible. 5. Rotor Inductance. The variation is ±50%. The traction effort curves show a small variation with the changes and in the opposite direction. Increased inductance implies a smaller traction effort while decreased inductance implies a larger tractive effort. In contrast with variation of core inductance, the variation of traction effort with rotor inductance remains about the same with increasing speed. For speeds below 30 mph, the variation in the efficiency curves are large and complicated, while above 30 mph, increased rotor inductance implies lower efficiency. The latter change is small. 6. Rotor Resistance. The variation is ±50%. The traction effort curves show an imperceptibly small variation with the changes and in the same direction. Increased resistance implies a larger traction effort while decreased resistance implies a smaller tractive effort. Above 15 mph, the traction efficiency variation with rotor resistance is very small. For power, 41

42 increase in rotor resistance yields decreased efficiency and decrease in rotor resistance yields increased efficiency. For electrical braking, the opposite is true. Below 15 mph, the electrical braking efficiency variation is more complicated. The next three parameters which influence the design of the motor are frequency at maximum voltage, maximum stator current and number of pole pairs. 7. Frequency at maximum voltage. The variation is ± 20%. The traction effort curves show a variation with the changes below the speed of 25 mph. The direction of the variation is as follows. Increased frequency implies a smaller traction effort while decreased frequency implies a larger traction effort. Above 25 mph, there is no variation. Below 25 mph, the traction efficiency variation with frequency variation is complex and significant. Above 25 mph, there is no variation. 8. Maximum stator current. The variation is ± 20%. The traction effort curves show a variation with the changes and in the same direction as the changes. Increased stator current implies increased traction effort and visa versa. These changes tend to decrease in value as the speed increases toward the maximum speed. Below speeds of 30 mph, the traction efficiency curves behavior with changing maximum stator current is rather complicated. Above speeds of 30 mph, there is a small decrease in efficiency with increasing maximum stator current. Of course, the maximum inverter current will limit the maximum stator current. 9. Number of pole pairs. The variation is one pole pair, so that 1,2,3 pole pairs are analyzed. Changing the number of pole pairs changes the motor characteristics directly. The traction effort curves show the variation with the changes in the number of pole pairs. Note also that pole changing is a method of speed control for an induction motor. The next category of parameters comprise the motor losses. There are four categories of motor losses connected with the induction motor model input. There are two friction loss components, which are connected with the dynamic rotation of the motor. These are coefficient 1, which determines losses proportional to the rotational speed of the motor and coefficient 2, which determines losses proportional to the square of the rotational speed of the motor. There is the windage loss, which is proportional to the cube of the rotational speed of the motor and is represented by another input coefficient. Finally there is the stray loss, usually expressed as a small fraction of input power to the motor. Each of these are summarized. 10. Friction loss coefficient 1. The variation is ± 50%. There is an extremely small, almost undetectable variation in the traction effort curves. The effect is to reduce the tractive effort and increase the electrical braking effort with increasing friction coefficient 1. The traction efficiency differences are also extremely small, which are less than Friction loss coefficient 2. The variation is ± 50%. Again, there is an extremely small, almost undetectable variation in the traction effort curves. The effect is to reduce the tractive effort and increase the electrical braking effort with increasing friction coefficient 1. The traction efficiency differences are also extremely small, which are less than Windage loss coefficient. The variation is ± 50%. There is an extremely small, almost undetectable variation in the traction effort curves. The effect is to reduce the tractive effort and increase the electrical braking effort with increasing friction coefficient 1. The traction efficiency curve 42

43 differences are also extremely small, but increase with increasing speed as a function of increasing windage coefficient. 13. Stray loss fraction. The variation is ± 50%. There is no difference in the traction effort curves. The traction efficiency curve differences are small, As expected, efficiency increases with decreasing losses and visa versa. 43

44 Gear Ratio (Variance = ±20%) Traction Effort Curves 44

45 Traction Efficiency Curves 45

46 Wheel Diameter The Wheel Diameter and Gear Ratio are linked in the expressions for Traction Efforts through the Torque of the motor and Linear Speed through the Rotary Speed of the motor through the ratio of Gear Ratio/Wheel Diameter as discussed in Section 3.1. Thus changing the Wheel Diameter and Gear Ratio in such a way that the ratio between these two parameters doesn t change will not change the Traction Effort or Efficiency Curves Motor Parameter Analysis Maximum Stator Current and Gear Ratio are the two parameters which influence the application of the induction motor for the service. 46

47 3.2 CONTROL PARAMETERS The following control parameters will be varied for the PWM Inverter. 15. Line Reactor Resistance 16. Main Device Forward Drop 17. Maximum DC Current 18. Modulation Frequency 19. Filter Capacitor Resistance 20. Free Wheeling Diode Forward Drop 21. Constant Losses 47

48 3.2.1 Line Reactor Resistance (Variance = ±50%) Traction Effort Curves 48

49 Traction Efficiency Curves 49

50 3.2.2 Main Device Forward Drop (Variance = ±50%) Traction Effort Curves 50

51 Traction Efficiency Curves 51

52 3.2.3 Motor Reactor Resistance (Variance = ±50%) Traction Effort Curves 52

53 Traction Efficiency Curves 53

54 3.2.4 Maximum DC Current The maximum DC current of the inverter is correlated with the maximum stator current of the AC Induction motor. Depending on the series/parallel configuration of the motors, the maximum current through the motors is always limited by the inverter. In the case at hand, two motors are fed by one inverter, so that the maximum stator current is equal to the maximum inverter current/2 or the maximum stator current, whichever is the smallest Modulation Frequency Neither the Traction nor Efficiency curves depend on the inverter modulation frequency, within the range of interest of the AC Drive. 54

55 3.2.6 Filter Capacitor Resistance (Variance = ±50%) Traction Effort Curves 55

56 Traction Efficiency Curves 56

57 3.2.7 Free Wheeling Diode Forward Drop (Variance = ±50%) Traction Effort Curves 57

58 Traction Efficiency Curves 58

59 3.2.8 Constant Losses (Variance = +1) Traction Effort Curves No difference in the traction curves Traction Efficiency Curves Very little difference in the traction efficiency curves. Difference is lest than Control Parameter Variation Analysis The parameters which are varied are shown in the PWM Inverter Model input screen and are listed in Section 3.2. Three of the parameters: Maximum DC Current, Modulation Frequency and Constant Losses are special and will be discussed first. 1. Maximum DC Current - The maximum DC current of the inverter is correlated with the maximum stator current of the AC Induction motor. Depending on the series/parallel configuration of the motors, the maximum current through the motors is always limited by the inverter. In the case at hand, two motors are fed by one inverter, so that the maximum stator current is equal to the maximum inverter current/2 or the maximum stator current, whichever is the smallest. 2. Modulation Frequency - Neither the Traction nor Efficiency curves depend on the inverter modulation frequency, within the range of interest of the AC Drive. 3. Constant Losses - There is no difference in the traction curves and an extremely small difference (less than ) in the efficiency curves. The remaining parameters; namely the Line Reactor Resistance, Main Device Forward Drop, Motor Reactor Resistance, Filter Capacitor Resistance and the Free Wheeling Diode forward drop were all varied by ± 50%, and all of them produced a very small to extremely small variation in the traction and efficiency curves. The direction of the variation is shown in the table below. Component TE EBE EFF Line Reactor Res ± ± " Motor Reactor Res " " " Filter Cap Res " ± " Main Device Fwd " " " FW Diode Fwd " ± " The symbols mean that when the parameter variation was ± then the traction effort or efficiency variation was ± or ". This is further clarified by viewing any particular comparison graph; for example. Even though the graphs are slightly separated one represents the + variation of the parameter, one represents the base and one represents the variation of the parameter. The overall conclusion is that the inverter has a very small effect on either the traction or efficiency curves. 59

60 3.3 GEAR UNIT PARAMETERS The following gear unit parameters will be varied. 22. Constant Power Term 23. Constant Torque Term 24. Torque Term 25. Speed Term 26. Speed Squared Term The first graph to be shown is the no gear losses case. 60

61 3.3.1 No Gear Losses Traction Effort Curves 61

62 Traction Efficiency Curves 62

63 3.3.2 Constant Power Term (Variance = ±50%) Traction Effort Curves 63

64 Traction Efficiency Curves No noticeable change in the traction efficiency curves. 64

65 3.3.3 Constant Torque Term (Variance = ±50%) Traction Effort Curves 65

66 Traction Efficiency Curves No noticeable change in the traction efficiency curves. 66

67 3.3.4 Torque Term (Variance = ±50%) Traction Effort Curves 67

68 Traction Efficiency Curves 68

69 3.3.5 Speed Term (Variance = ±50%) Traction Effort Curves 69

70 Traction Efficiency Curves 70

71 3.3.6 Speed Squared Term (Variance = ±50%) Traction Effort Curves 71

72 Traction Efficiency Curves 72

73 3.3.7 Gear Unit Parameter Variation Analysis Gear unit losses result from friction, which has many components, which are described in the gear unit model. The first variation to consider is the no loss state as compared to the normal state or base case. The traction effort curves show a small change. The tractive effort curve is slightly higher than normal and the electrical braking effort curve is slightly lower. This is what is expected since some of the tractive effort must overcome the friction and the friction helps in the case of electrical braking. The traction efficiency curves also show a small change. These changes vary from 1-7% depending on the speed of the rotation, which is proportional to the speed of the train. The following remarks cover the remaining components: 1. Constant Power Term. Variation! 50%. There is an extremely small change in the traction effort curves and an undetectable change in the efficiency curves. 2. Constant Torque Term. Variation! 50%. There is an extremely small change in the traction effort curves and an undetectable change in the efficiency curves. 3. Torque Term. Variation! 50%. There is a small change in the traction effort curves. There is also a small change in the traction efficiency curves. The change is relatively constant over the speed range. 4. Speed Term. Variation! 50%. There is a small change in the traction effort curves. This change becomes slightly larger as the speed increases. There is also a small change in the traction efficiency curves. The change becomes substantially larger as the speed increases. 5. Speed Squared Term. Variation! 50%. There is an extremely small change in the traction effort curves. There is also a small change in the traction efficiency curves. The change becomes slightly larger as the speed increases. The principle contributors are the Torque term and the Speed term. The net effect is to push up the losses as the speed increases. 73

74 4 VOLTAGE VARIATION 4.1 INTRODUCTION Traction Effort and Efficiency Curves can be computed in two general ways. o Constant voltage curves, where the computation is effected at constant line voltage, normally, open circuit voltage, minimum voltage or maximum voltage. o Power variation voltage curves, where the voltage varies with the power drawn. The term nominal voltage as used here refers to a constant voltage at which the Traction Effort and Efficiency Curves are computed. Nominal voltage is taken somewhere between maximum voltage and minimum voltage. The open circuit voltage is the voltage measured between the catenary, third rail or trolley and the track, when there is no operation on the line. The latter case of power variation voltage curves is most realistic, since as the more power is drawn, the voltage generally varies as the inverse of the power drawn. The line voltage varies as a result of the current being drawn by the train as well as the currents being drawn by all of the other trains on the power system feeding the trains. Most models used in power systems studies do not take line voltage variation into account. Maximum voltage drops and performance are usually obtained by assuming a constant voltage for the train, which can range from open circuit voltage to minimum voltage allowed on the line. If a power system is designed on this basis, it can be either designed conservatively or liberally depending on the selection of this voltage. A conservative design will use a nominal train voltage close to the open circuit voltage, while a liberal design will choose the nominal voltage, which is lower. Choice of this voltage will also determine the schedule performance and energy consumption of the train. A second point which must be taken into account is that the efficiency of a traction drive in a train varies with both the traction effort and speed, so the conversion of mechanical power developed at the wheels to electrical power at the line is different depending on the nature of the traction drive itself. This means that this drive, whether it be an AC Drive or not, must be modeled to take this variation into account. When traction drive manufacturers supply equipment, they generally provide a single traction curve at some constant voltage as function of speed, together with line current as a function of speed. This is usually provided as the maximum traction effort curve; namely, the maximum traction efforts that can be developed at particular speeds, given that constant voltage. Finally, a third and final point is that depending on the train weight and its acceleration rate, the full traction efforts are not necessarily used, so that even if the line voltage does drop as more power is drawn, the traction drive may have the capability to draw more current from the line in order to maintain performance. This is certainly true of AC Drives. As a consequence, unless some form of current limiting is added to the system, as the line voltage drops, the drive works harder to maintain the performance, which drops the line voltage more. The TOM has the capability of developing traction and efficiency curves where the line voltage varies with the power drawn. This simplification does not exactly simulate the actual situation, but is a shortcut for quickly estimating power system performance for a design. If the nominal voltage is set high, the system evaluation will be more conservative and if set low will be more liberal. Both cases, nominal voltage and voltage variation with power are considered, and traction effort and efficiency curves are displayed under these conditions. 74

75 The problem of true performance simulation requires that both the traction efforts and efficiencies be computed with the actual voltage seen at the line input of the train, which depends the present performances and positions of all of the other trains on the power system. This problem is complex and time consuming and should not be the basis for power system design evaluation, since it depends on specific conditions. Since the power system is an important link in the overall performance of the rail system, the design should tend toward the conservative side. This portion of the study uses a very simple test track, called the AC Drive Test Track, to obtain a feeling for the numbers involved. This section develops Traction Effort and Efficiency Curves for both constant voltage and voltage variation with power drawn cases. Section 5 considers the performance of these models using the simple AC Drive Test Track. 75

76 4.2 CONSTANT VOLTAGE CURVES All of the curves computed and graphed in Section 1 and 3 were at the constant voltage of 750 volts. This is the open circuit voltage. Any of these could have been computed at any voltage. The following graph shows the curves computed at 750, 650, 550 and 450 in order to compare the variation Traction Effort Curves 76

77 4.2.2 Traction Efficiency Curves 77

78 4.3 VOLTAGE VARIATION WITH POWER The assumption is made that the Traction Effort and Efficiency Curves vary with the voltage at the line, which varies between (maximum, minimum)voltage as the power varies between (minimum, maximum), an inverse relationship between voltage and power. Thus the performance will vary according to the line voltage, which in turn depends on the power drawn. This could result in a better simulation of the actual performance of the train as the voltage drops. This will also occur in electrical braking. Four cases are considered for voltage variation. These four scenarios are described in the next table. Case\Condition Maximum Voltage Nominal Voltage Minimum Voltage The two cases with maximum voltage at 850 are appropriate to regeneration turned on and the cases with maximum voltage at 750 are appropriate to regeneration turned off. In all cases the open circuit voltage is 750. In each of these cases, the curves will also be computed at nominal voltage and displayed as a comparison point. 78

79 4.3.1 Variable Voltage Case 1 (Max 850 Nom 700 Min 450) Traction Effort Curves 79

80 Traction Efficiency Curves 80

81 4.3.2 Variable Voltage Case 2 (Max 850 Nom 650 Min 450) Traction Effort Curves 81

82 Traction Efficiency Curves 82

83 4.3.3 Variable Voltage Case 3 (Max 750 Nom 700 Min 450) Traction Effort Curves 83

84 Traction Efficiency Curves 84

85 4.3.4 Variable Voltage Case 4 (Max 750 Nom 650 Min 450) Traction Effort Curves 85

86 Traction Efficiency Curves 86

87 5 VOLTAGE VARIATION PERFORMANCE 5.1 AC Drive Test Track The AC Drive Test Track is used to compare voltage variation performance with constant voltage performance. The system is very simple. It is one track between two stations Begin and End as shown in the layout. The two substations are both 5 MVA with 6% impedance and open circuit voltage of 750 v. Loop track resistance is Ω/mile. The loop substation connection is Ω. The Unit Voltage is set as 750 v and the Unit Power is set at 5 MW. Train accelerating and braking rates are set at 3 mphps with no jerk limit. The train has the following characteristics: 6 car train All cars powered with same AC Drive Auxiliary Power 30 kw/car Empty Weight 36 tons/car Crush Load Weight 52.5 tons/car Car length 75 feet Wheel Diameter 28 inches 4 Axels per car. Gear Ratio Davis Train Resistance o Frontal area 85 ft. o Flange coefficient.071 lbs/ton/mph o Front Car Aerodynamic coefficient lbs/ft^2 /mph^2 o Trail Car Aerodynamic coefficient lbs/ft^2 /mph^2 87

88 5.2 TPS INPUT FILES Control File The control file is CL-+.acd Train Files The Train files are defined by their electrical and performance parameters. The files under Efficiency Matrix (2x20) represent the case where efficiencies are given at full traction efforts. This is the case normally given by the manufacturers. The files constructed by the TOM using the full capability of the built-in Propulsion Model are listed under Efficiency Matrix (20x20). The latter Train files develop efficiencies at twenty intermediate points between Traction Effort = 0 and Full Traction Effort as given by the traction effort curves Station Files There are only two station files, one representing an empty train and the other representing a crush loaded train. o ST-e.acd (Passenger Load Factor = 0) o ST-f.acd (Passenger Load Factor = 100) Grade and Curve Files There is one grade file representing level track. GR-l.acd There is one curve file representing tangent track. CU-t.acd Speed Restriction File There is one speed restriction file representing a speed limit of 70 mph everywhere. SP-70.acd 88

89 5.2.6 Route File There is one route file representing running on track 1. RU-1.acd File of Filenames Files The File of Filenames files for empty and crush loaded trains are listed. Note that these names are also used for the ENS File of Filenames files. TPS and ENS output files also have the same name designation. 89

90 5.3 ENS INPUT FILES Network File One Network file is used. The network was described in Section 5.1. The file is N-l.acd Operating Time File Only one Operating Time file is used in order to run a minute and 15 seconds. OP-l.acd Train Location File Only one Train Location file is used since the empty and full trains do not run at the same time. TL-s.acd Current Measurement Input Files Only one Current Measurement Input file is used. This measures current at the middle of the test track at position 0.5. AM-c.acd Power Profiles The Power Profiles are identified the same way as the File of Filenames files. These outputs from the TPS are inputs, one at a time into the ENS ENS File of Filenames Files These were defined previously in Section

91 5.4 TPS RESULTS Run Times The test track run time is listed for all of the TPS runs. The run times are the same for each row, since the Traction Effort Curves are the same. Only the Traction Efficiency Curves or whether regeneration is on or off is different. The latter do not effect run time. In both cases, empty or crush loaded trains, the run time increases as the voltage decreases. This observation is readily explained. In all cases, the tractive effort for a given speed is less. The voltage variation cases yield run times between 450 and 550 v. If the open circuit voltage is 750, traction standards of 25% indicates that the minimum should be no lower than Finally, crush loaded train runtimes are always larger than empty train runtimes. This is expected. 91

92 5.4.2 Energy of Run The energy used in the run is tabulated for all of the TPS runs. The difference between Regeneration On and Regeneration Off is expected. Of course, when running the TPS, the energy of regeneration (-) during braking subtracts from the energy when powering (+). For the Regeneration Off cases, the run energy decreases as the as the voltage and hence the performance (run time) decreases. This is what is expected. With the Regeneration On cases, it remains about the same kwh. 92

93 5.5 PEAK POWER AND MINIMUM VOLTAGE Running the ENS for the test track produces typical graphs of the form shown. The ENS runs were completed with the Regeneration Off condition and for both empty and crush loaded trains. This graph shows that the maximum voltage is v and the minimum voltage is v. The important results are laid out in the tabular form. In addition to identifying each of the runs, the entries in the table are: Time(sec) into the run at which peak power occurs. Speed(mph) of the train at peak power point. Position(mi) of the train at peak power; note the train starts at mp 0.2 Acceleration(mphps) of the train at peak power point. Tractive Effort(klb) of the train at peak power point. Minimum Voltage(v) on the train during the run. Position(mi) at which minimum voltage on the train occurs. 93

94 5.6 SELECTION OF A VOLTAGE VARIATION SCENARIO At the present time, the TOM does not have the capability of using the actual line voltage to determine the performance of the train. Computationally, this is an iterative procedure in which the train performance is adjusted with the line voltage until the line voltage and voltage at which the performance is calculated are the same. As mentioned previously, this is a time consuming procedure. It must begin when the first train leaves the terminal according to the timetable, since the positions of all trains on the line cannot be determined beforehand as is presently done with the TOM. The procedure proceeds as follows: 1. Initially guess that all trains on the line have open circuit voltage. 2. Run a partial TPS on every train on the system given their voltage, position and speed, determine the traction effort necessary to advance them one increment in time, subject to the wayside conditions (grade, curve, speed restriction or command, route). 3. Use traction efficiencies for each train to determine the power at the line. 4. Run a partial ENS to determine voltages at all of the trains. 5. Do these voltages agree with the previous voltages used for the TPS. 6. If all voltages agree, within some level of accuracy go to 7, if not go to Determine all salient powers, currents and voltages. 8. Increase time by one increment. 9. If the end time is reached go to 9, if not go to Summarize and quit. Since the procedure is extremely time consuming, many scenarios cannot be tried for a fixed time interval. As computer speed increases in the future, this will become less true. The alternate way around this is to use the present method of running the TPS and ENS separately, and making the assumption that the major portion of the voltage drop on the line comes from the train drawing the power. This assumption will allow the use of performance in which the line voltage varies inversely as the power drawn or given to the line. This capability is built into the propulsion model of the TOM. An example is provided using the AC Test Track. This procedure uses the routine of steps 1 through 10, described previously in a manual procedure. Two cases will be illustrated, the first case uses a simple 2x20 efficiency matrix for the propulsion system efficiencies while the second case uses a finer mesh modeling in a 20x20 matrix Voltage Variation Scenario 2x20 Efficiency Matrix Begin with the File Construction Module-Train File Input-Electric Propulsion Model Input 94

95 The 0 th run or start of the process begins with developing the train file at open circuit voltage. This train file is incorporated into a TPS run followed by an ENS run after which the minimum voltage on the line is determined. The nominal voltage is the new train file is chosen to be halfway between the minimum voltage just determined and the open circuit voltage. The maximum voltage remains the same. This process is repeated until convergence is obtained as shown next. It turns out that the convergence of the process is independent of the choice of nominal voltage algorithm as long as it lies between the open circuit and minimum voltage. 95

96 5.6.2 Voltage Variation Scenario 20x20 Efficiency Matrix The results for the finer mesh 20x20 efficiency matrix is shown next. The minimum and nominal voltages are lower in this case than in the previous case Performance Characteristics Train Performance Simulation Results The schedule time and energy results are shown together with the previous cases of crush loaded trains. 96

97 Electric Network Simulation Results Results from the ENS are posted below along with the original ones. 97

98 6 DESIGN OF AC DRIVE FOR THE COMPUTER LAB OF THE TOM TRAINING COURSE 6.1 INTRODUCTION One of the problems in the Computer Lab portion of the TOM Training Course is to develop a Train File based on an AC Drive using the Electric-Model input option in the File Construction Module Train File Input - Main Screen. The power cars of this train must be capable of working together with the CAM Control cars that were developed during an earlier portion of the Computer Lab. Thus the Tractive Effort Curve of the AC Drive cars must be such that it can be modified by microprocessors to be exactly the Tractive Effort Curve of the CAM Control cars. This requirement follows from the requirement that a mixture of the cars (AC Drive and CAM Control) do not develop coupler forces. The cars should have the same performance. This requirement means that the Tractive Effort Curve of the AC Drive car without microprocessor modification must be greater than that of the CAM Control car at all speed points. Thus microprocessor modification will reduce the AC Drive Tractive Effort Curve to that of the CAM Control. The AC Drive car, so designed, should be as energy efficient as possible, in both no regeneration and regeneration condition. 6.2 BASE CAR CAM CONTROL The base car is a CAM Control car, as specified in Train File T-6r.new. Train File Input screens from a six car train are shown next. 98

99 99

100 A graph of the Tractive Effort Curve is shown next. 100

101 101

102 6.3 MODEL NAME CONVENTION Three model files will be needed to build the AC Drive train. 1. U-ACEX.mot AC Induction Motor Model File. 2. U-ACEX.con PWM Inverter Model File 3. U-ACEX. Gum Gear Unit Model File The Train File will be named T-6a.new. These files will be developed in the next section. 6.4 TRACTION CURVE MATCHING Begin with the files W-ACDR.mot, W-ACDR.con and W-ACDR.gum. Also begin with the File Construction Module Train File Input Main Screen for the New Rail System. Import the file T-6r.new by a double-click on it in the Train Input File file list box. 102

103 Make the following changes on the Main Screen. 1. Change the Type of Propulsion System to Electric Model. 2. Change the Train Part of Name text box to 6A. 3. Change the Name of File name text box from 6r to 6a. 4. In the File Caption text box, change Cam Control to AC Drive. Click the Propulsion Input check box. 103

104 Make the following changes on this screen. 1. Set Number of Spd Points text box to Set Number of TE Points text box to Set the No Regeneration combo box to Regeneration Click the Compute from Model check box. 104

105 Set the Electric Propulsion Model Input screen to the following completed screen. Click the Gear Model check box. 105

106 Double-click on the W-ACDR.gum file in the file list box. Click the Select command button. 106

107 Click the Select command button. Click the Select command button. 107

108 Click the Create File command button. Click the Yes command button to review the file. 108

109 Scroll to bottom. The next step is to compare the Tractive Effort Curve of the AC Drive car with that of the CAM Control car. 109

110 In the shaded area of the graph, the CAM Control Tractive Effort Curve exceeds that of the AC Drive. Variation of Frequency at Maximum Voltage, Gear Ratio and Maximum Stator Current produced the following Tractive Effort Curve. 110

111 The parameters for the Computer Lab AC Drive (U-ACEX) were changed from the original AC Drive (W-ACDR) as follows. Parameter Change From Original AC Drive Original Modified Motor W-ACDR U-ACEX Maximum Stator Current (amps) Frequency at Maximum Voltage (hz) PWM Inverter W-ACDR U-ACEX Maximum Inverter Current Gear Unit W-ACDR U-ACEX Gear Ratio EFFICIENCY RUNS WITHOUT REGENERATION TPS runs were made for the NEW Rail System with and without regeneration turned on. The following tables show the results. Normal operation is the CAM Control. Normal Operation AM Peak Terminal to Terminal Run Time Energy (minutes) (kwh) Rock Garden Noel's End Noel's End Rock Garden Rock Garden Fenton Harbor Fenton Harbor Rock Garden AC Drive Operation AM Peak (No Regen) Terminal to Terminal Run Time Energy (minutes) (kwh) Rock Garden Noel's End Noel's End Rock Garden Rock Garden Fenton Harbor Fenton Harbor Rock Garden AC Drive Operation AM Peak (Regen) Terminal to Terminal Run Time Energy (minutes) (kwh) Rock Garden Noel's End Noel's End Rock Garden Rock Garden Fenton Harbor Fenton Harbor Rock Garden FINAL DESIGN The final design of the AC Drive of the Computer Lab is presented in three files. 1. U-ACEX.mot 2. U-ACEX.con 3. U-ACEX.gum 111

112 These files are now shown imported into their appropriate model screens. 112