Three Phase Technology Book PDF

 COURSE ON THREE PHASE TECHNOLOGY IN TRS APPLICATION INDIAN RAILWAYS INSTITUTE OF ELECTRICAL ENGINEERING NASIK ROAD  PREFACE There has been lot of technological developments using Three phase Technolo...

 COURSE ON THREE PHASE TECHNOLOGY IN TRS APPLICATION INDIAN RAILWAYS INSTITUTE OF ELECTRICAL ENGINEERING NASIK ROAD  PREFACE There has been lot of technological developments using Three phase Technology in the field of Electrical Traction Rolling Stock. Hence, it has become necessary to compile all relevant technical matter on the subject of Three Phase Technology in to a concise book, which is named as “Traction Rolling Stock : Three Phase Technology.” For bringing out this book Shri K.V. Gaikwad, Sr. Section Engineer and Shri Suryawanshi M.A., Raj Bhasha Supdtt. have made substantial efforts, under the guidance of Shri Rupesh Kumar, Professor (Electronics). I am very glad to note that lot of efforts have been made in bringing out this book of “Traction Rolling Stock : Three Phase Technology “ in the present form. I am sure that this book will serve the needs of Electrical Engineers working in the field of Electrical Traction Rolling Stock. Nasik Road 18th August, 2010 A.K. RAWAL DIRECTOR TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 3  INDEX Sr. No. Subject Page No. 01. Three phase Technology in TRS application 05-17 02. Three phase ABB locomotive – System information 18-34 03. Description of Power circuit 35-42 04. Power Converter 43-59 05. Description of Auxiliary circuit 60-63 06. Auxiliary Converter 64-76 07. Control Electronics & Vehicle diagnostic system 77-95 08. Pneumatic system 96-112 09. Bogie design features 113-116 10. Comparative performance 117-119 11. AC DC 3-Phase EMUs 120-138 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 4  1. THREE PHASE TECHNOLOGY FOR TRACTION APPLICATION 1.0 INTRODUCTION Three phase AC drive technology has become very common and significant for modern rail vehicles. These vehicles are equipped with GTO thyristors and microprocessor control systems. Microprocessor is used for vehicle control, supervision of health and operations of all major components and diagnostics. It permits electric breaking down to standstill and selection of best PWM technique for improved performance of motor as well as unity pf. The advantages associated with this technology are evident in technical as well as economic aspects. 2.0 WHAT‟S NEED FOR A CHANGE ? Earlier, all the locomotives were using DC traction motors. The speed/torque regulation is achieved by using either tap changer on transformer or through resistance control on majority of these locomotives. Conventional relay based protection schemes are used. In most of the cases, the driver uses his discretion to diagnose and get past the problem. 2.01 FRPCPY for Tap changer and its associated equipments is about 10%. 2.02 DC motor has inherent problems of brush gear, commutator and low power to weight ratio. DC motor is essentially a high current low voltage design which calls for expensive large diameter cables and large electro-pneumatic reverser, contactors, switches etc. 2.03 Thyristorised DC traction motor drives, though made the DC motor drive more efficient, suffer because of high harmonic injection into Power supply. Loss associated large filters had to be carried on Locomotives to overcome this. 2.04 Emphasis on regeneration is increasing day by day to reduce energy bill as well as to save energy for greater national cause. 2.05 With ever increasing need for hauling higher loads, there is need to make maximum use of available adhesion. 2.06 There is need for track friendly locomotives to reduce track maintenance efforts. 3.0. WHY THREE PHASE TECHNOLOGY? Advantage of 3-phase induction motor over DC series motor 3.01 Three phase traction motors are robust and require little maintenance. Apart from bearing, it has no parts subjected to wear. It is insensitive to dust, vibration and heat. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 5 3.02 No restriction on speed of motor in absence of commutators, AC traction motors can easily operate at 4000 rpm in contrast to 2500 rpm in case of DC machines. 3.03 The limit imposed due to bar-to-bar voltage for DC commutator motor is no more relevant with squirrel cage induction motors. Whole power flow from transformer to converter to DC link and down to inverter / motor may be chosen at higher operating voltage. Against nominal 750 V, 1000A system with DC machines equivalent three phase propulsion is configured around 2800 V, 300A. Due to heavy reduction in operating current, power cables are much lighter and losses are reduced. 3.04 Power to weight ratio of induction motor is much higher than the DC motor. As a typical example 1500 KW per axle can be packed per Axle with induction motors compared to 800 KW maximum with DC motors. 3.05 Since the torque speed characteristic of the induction motor is markedly steeper than that attainable by conventional Dc machines, the induction machine can take better advantage of maximum possible tractive effort. A high mean adhesion coefficient can be expected. 3.06 As the adhesion coefficient is high, it is possible to transfer a part of the braking forces for the trailing load to electric brakes of locomotive. That is, in the case where regenerative braking is used, the regenerated electric energy can be increased. 3.07 High power/weight ratio of induction motor, reduction in cable thickness, reduction in number of contactors, switches etc. result in reduction in physical dimension and weight of the entire system. Advantages of microprocessor based control. 3.08 Almost all moving contactors, switches, relays, reversers etc. are eliminated and operation is sequenced by means of solid state logic. 3.09 The microprocessor is used for drive control. The microprocessor allows the redundancy to be built in controls rather than the power equipments. 3.10 Microprocessor based fault diagnostic system guides driving crew about the fault location and suggests remedial action. It also keeps records of faults, which can be analysed by shed staff later. 3.11 Microprocessor control software has flexibility to provide software-based solution to local operational needs. Other advantage of three phase drive 3.12 The induction motor drives are about 20% energy efficient compared to DC drives. 3.13 Three phase drives allow regeneration and unity power factor operation. The energy saving due to regeneration and improved power factor are sizable. 3.14 Electric braking down to standstill is possible. It improves operational efficiency besides reduction in maintenance efforts. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 6 4.0 THEN, WHY SO LATE ? To achieve these advantages of induction motor, it is necessary to supply it with a three phase variable voltage variable frequency (VVVF) source. This could not be achieved under technically and economically feasible conditions, until the advent of GTOs and microprocessor based control system in the last few years. 5.0 SO NICE, NOW DETAILS PLEASE ? 5.01 Three phase induction motor. To appreciate the complexity of the drive for using 3 phase squirrel cage induction motor for traction application, let us start with speed torque characteristic of a conventional fixed frequency, fixed voltage squirrel cage induction motor shown in fig. 1.1. It is described by following equation. T = K (V / F) ² * fS Where V & f are terminal voltage and frequency of supply to induction motor, fS is slip frequency and T is torque developed. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 7   Though, the starting current of typical cage rotor induction motor is 5 to 6 times rated current, the starting torque is small because of the low power factor.  Regeneration takes place, only when rotor is driven mechanically at super synchronous speeds. Variable voltage variable frequency drive In adjustable frequency drive, the supply frequency is reduced for starting, this frequency reduction improves the rotor power factor and this increases the torque/ampere at starting. In this manner, rated torque is available at start and the induction motor is accelerated rapidly to its operating speed by increasing the supply frequency. This method also avoids danger of low frequency crawling, which sometimes occurs when induction motors are started on fixed frequency supply. Fig.1.2 shows T.S. characteristic for constant v/f (constant air gap flux) at different supply frequencies. The breakdown torque is maintained constant by maintaining v/f constant. The stator voltage cannot be increased beyond rated voltage. With voltage remaining fixed further, as frequency is increased above base or rated motor speed, the air gap flux and breakdown torque decreases, as shown in fig.1.3. These characteristics are suitable for traction applications, where a large torque is required below base speed and a reduced torque is sufficient for high speed running. The torque-speed characteristic for a practical traction drive system evolved from the above two strategies is shown in fig.1.4. The variation in motor voltage & current, slip freq. and torque as the function of speed for operating regions shown in fig.1.4 is shown in fig.1.5. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 8 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 9 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 10 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 11  Fig. 2.2 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 12 5.02 Three phase induction motor drive The block diagram for such an induction motor drive is shown in fig.2.1 Motor-end inverter can be a current source inverter or a voltage source inverter. In the past, when conventional thyristors were the only choice, designers opted for current source inverter. About 70% of all underground railways and light rail transport in the world today are partly or fully equipped with this technology. The voltage source inverter, which required very complicated control electronics, when equipped with thyristors did not become a paying proposition until the development of GTOs and microprocessor based control techniques. The circuitry of the input converter which provides a DC supply for the load side converter depends on the following: 1) Type of input power supply i.e. AC or DC. 2) Electricity utility‟s limits on reactive power harmonics. 3) Type of electric brakes; that‟s regenerative, rheostatic or both. Fig.2.2 shows power schematic of ABB three phases AC locomotive. The following stages are involved in power conversion.  AC voltage is stepped down by main transformer.  AC to DC conversion and boost up by 2.0 to 2.5-boost factor by means of front-end converter.  Filter stage to reduce ripple in rectified DC.  Link over voltage protection. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 13 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 14 5.03 Microprocessor control VVVF inverter and four quadrant converter controls are quite complicated. Hardware for this control, if configured with convention equipment, will be complicated with large physical dimensions. Microprocessors are adopted as hardware optimization tool in order to make an improvement in this area. The principal features of the microprocessors control are as follows: a) The space, weight and power consumption of the control unit can be reduced. b) It is possible to execute high degree processing operations for control easily, accurately and at high speed, using software. c) Failure occurring in the circuit, if any can be easily identified by self-diagnostic function. Microprocessor technology is used for control of whole vehicle including  Driving and braking control with automatic speed regulation.  Supervision of all functions and for the operation of all major components of locomotive with automatic changeover or shutdown in the event of failure.  Diagnostic system for all electrical and electronic devices on the vehicle.  Inversion of DC to variable frequency AC by means of drive end inverter. We shall now discuss briefly the modules used in 3 phase ABB locomotive. a) Voltage source inverter. A voltage source single pulse inverter is used for supplying variable voltage from 0 to 2180 V and variable frequency from 0 to 160 Hz. b) DC link DC link is made of the DC link capacitor, series tuned filter and over voltage protection circuit. DC link is reservoir of energy, which supplies periodic and non- periodic energy requirement of load and decouples it from supply source. The task of the DC link capacitor is to supply the reactive power needed by induction motor. The current supplied to DC link by 4-Q converter consist of second order harmonics, which is absorbed by series tuned filter. c) Input side converter. A 4-quadrant pulse width modulated converter is used for converting the AC to DC. It is capable of obtaining unity power on line current using proper control strategy and thereby eliminating the need for separate power factor correction equipment in the locomotive. Further more, the line current has insignificant harmonic content so that signaling and telecom circuits are disturbed. The principle of working of the converter is explained in the diagram given in fig.3.1. The input voltage to the converter Ec is controlled by pulse width modulation of DC TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 15  link voltage Ed. The fundamental component of the modulated voltage Ec acts against source voltage Es as shown in equivalent circuit of fundamental component. The converter input current Is in quadrature with EL i.e. voltage across reactor. Since Es is equal to Vector sum of EL & EC, it is possible to ensure that IS is in phase with ES by changing amplitude and phase of EC through PWM and thus achieve unity PF. It could be seen that fundamental component of EC is nothing but modulating wave itself. Thus by controlling the modulating wave, it is possible to achieve the unity pf. 5.04 Diagnostics. The structure of the diagnostic system on these locomotives can be distinctly dived into three portions: 1) Hardware of the diagnostic system is based on 80186/16-bit microprocessor and is programmed similar to main processor. All data in main processor is also available to diagnostic Hardware for analysis. 2) Firmware is project-independent software. This takes care of special task to be performed by hardware. The firmware processes and stores the diagnostic messages. It can be viewed as the expert system for diagnostic computer. 3) The application software on the other hand is project dependent. It is written to take care of varying working conditions. It defines the rules for the expert system which evaluates and stores the diagnostic messages. Diagnostic system processes the data available and classifies the diagnosis into three levels. These levels are programmed based on running experience of locomotives. Level I: Audio visual indication and record only. For faults in level-I category, the diagnostics will automatically take necessary corrective action to maintain normal locomotive operation. Wheel slip, oil temperature reaching maximum limit, DC link over voltage etc. fall under this category. Level II: Audio – Visual indication and one bogie isolation. This kind of action is taken when the fault is in major equipment of any one bogie. The faculty bogie is isolated and thereafter power to the locomotive is supplied by only one bogie. Examples are earth fault of DC link, opening of tuned filter, failure of traction motor, converter etc. Level III: Audio visual indication and locomotive shut down. This indicates eventual failure of equipment associated with both the bogies. Such faults are associated with malfunctioning of main circuit breaker, transformer, mechanical breakdown etc. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 16 5.05 Instrumentation A highly sophisticated data acquisition system using state of art instrumentation is used all over the locomotive. 5.06 Braking Regenerative braking down to standstill is possible reducing the break shoe wear. 5.07 Pneumatic system A new modular pneumatic panel supplied by Devis and Matcalfe & SAB-WABLO is used on these locomotives. Triplate structure of pneumatic panel has significantly improved reliability of pneumatic system. It uses brake electronics compatible with MICAS operating system. 5.08 Bogie and suspension system Flexi float bogie with two stage suspension is used for track friendly design. Fully sprung traction motor in passenger locomotive with significantly reduce stress on track. 5.09 To Sum up…. The three-phase technology brings together state of art technologies in the area of devices, control, instrumentation and communication. It puts up great responsibility on all of us to equip ourselves to assimilate this technology, as it will soon pervade other areas like AC/DC traction, EMUs etc. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 17  2.THREE PHASE ABB LOCOMOTIVE SYSTEM INFORMATION EQUIPMENT LAYOUT The locomotive is modular in construction. Locomotive assembly consists of five main parts (Ref. Fig 2.1): - 1. Roof 2. Driver‟s cab 3. Machine Room 4. Bogie 5. Frame Layout of roof equipment The equipments which are on the primary side of the transformer are mounted on the roof (Ref. Fig.2.2). These equipments are:- 1) Pantograph for current collection. 2) Internal air filter panel for oil cooling unit. 3) 25 KV Bushing. 4) Surge arrester. 5) Earthing switch. 6) Vacuum circuit breaker. 7) Primary voltage transformer. 8) Resistance box for harmonic filter. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 18 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 19 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 20 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 21 Layout of machine room equipment Machine room, is between both the drivers cab with a central corridor. All the cooling blowers, main converters, auxiliary converters & control cubicles are fitted in the machine room. These equipments are fitted symmetrically on both sides of the central corridor. The detailed layout of the machine room equipment is given in fig. 2.3 Layout of cab-equipment Overview of the driver‟s cab is shown in fig. 2.4 Layout of underframe equipment Main traction transformer, compressors, air dryer, air reservoirs and batteries are mounted in underframe of the locomotive. Detailed layout of the underframe equipment is shown in fig. 2.5 Fig. 2.5 Under frame layout 1. Main compressor 2. Transformer 3. Circuit breaker battery 4. Battery box TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 22 TECHNICAL PARTICULARS FOR WAP5 LOCOMOTIVE 1.1. Guaranteed performance at 22.5kV and half worn wheel: (i) Starting tractive effort 258 kN (ii) Continuous rated tractive effort in 220 kN the speed range of 0-50 km/h (iii) Continuous rated speed 50 km/h (iv) Continuous rated power at wheel 4000 kW rim in the speed range of 80-160 km/h (v) Maximum regenerative braking effort 160 kN (10-90 km/h) (vi) Maximum service speed 160 km/h 1.2 Arrangement: (i) Axle arrangement Bo-Bo (ii) Traction motor mounting Fully suspended on bogie frame (iii) Brake system Air, regenerative and parking brake for loco (iv) Control circuit voltage 110 Vdc (nominal) 1.3 Important dimensions: (i) Total weight 78.0± 1% tones plus max.800 kg including harmonic filter and side buffers (ii) Axle load 19.5± 2% tones (iii) Unsprung mass per axle Limited to 2.69 tonnes (iv) Wheel Dia. - new 1092 mm -half worn 1054 mm -full worn 1016 mm (v) Gear ratio 3.941 (67:35:17) (vi) Length of loco over buffers 18162 mm (vii) Length of loco over headstock 16880 mm TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 23 (viii) Bogie center distance 10200 mm (ix) Loco wheel base 13000 mm (x) Bogie wheel base 2800 mm (xi) Overall width of the body 3144 mm (xii) Length of cab 2434 mm (xiii) Panto locked down height 4255 mm (xiv) Height of C.G. from rail level 1393 mm 1.4 Other salient features: - 3-phase drive with GTO thyristors and MICAS-S2 microprocessor based control system. - The design provides for increasing the service speed potential to 200 km/h in future by changing the gear ratio. - Hotel load winding on loco to feed coach converters. - Provision for multiple unit operation of two locomotives. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 24  Fig. 2.6 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 25  Fig. 2.7 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 26  Fig. 2.8 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 27 TECHNICAL PARTICULARS FOR WAG9 LOCOMOTIVE 1.1 Guaranteed performance at 22.5 kV and half worn wheel: (i) Starting tractive effort 460kN (ii) Continuous rated tractive effort in 325 kN the speed range of 0-50 km/h (iii) Continuous rated speed 50 km/h (iv) Continuous rated power at wheel 4500 kW rim in the speed range of 80-160 km/h (v) Maximum regenerative breaking effort 260 kN (10-62 km/h) (vi) Maximum service speed 100 km/h 1.2 Arrangement: (i) Axle arrangement Co-Co (ii) Traction motor mounting Axle hung, nose suspended (iii) Brake system Air, regenerative and parking brake for loco Air brake for train. (iv) Control circuit Voltage 110 Vdc (nominal) 1.3 Important dimensions: (i) Total weight 123.0 ± 1% tonnes (ii) Axle load 20.5 ± 2% tones (iii) Unsprung mass per axle 3.99 tonnes (iv) Wheel Dia. - new 1092 mm - half worn 1054 mm - full worn 1016 mm (v) Gear ratio 5.133 (77:15) (vi) Length of loco over buffers 20562 mm (vii) Length of loco over head stock 19280 mm (viii) Bogie center distance 12000 mm (ix) Loco wheel base 15700 mm TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 28  (x) Bogie wheel base 1850 + 1850 mm (xi) Overall width 3152 mm (xii) Length of cab 2434 mm (xiii) Panto locked down height 4255 mm (xiv) Height of C.G. from rail level 1349 mm 1.4 Other salient features: - 3-phase drive with GTO thyristors and MICAS – S2 microprocessor based control system. - Provision for multiple unit operation of two locomotives. - Provision for ballasting to increase the loco weight to 135 tones in future. - The design permits interfacing and provision of “inching control” in future. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 29  Fig. 2.9 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 30  Fig. 2.10 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 31  Fig. 2.11 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 32  Fig. 2.12 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 33  Fig. 2.13 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 34  3. POWER CIRCUIT DESCRIPTION (Refer Fig. 3.1 & Fig. 3.2 ) The locomotives WAP5 and WAG9 are having 3-phase drive with GTO thyristors and microprocessor based control system. The primary winding of the main transformer is fed from the OHE (25 kV, single phase ac, 50 Hz) through the pantograph (1) and the vacuum circuit breaker (5). Two surge arrestors (9/1 & 9/2) are provided on the roof – one at the pantograph end and the other after the VCB. A primary voltage transformer (6.1) is provided at the primary side of the main transformer (7) to monitor the overhead catenary voltage. Signal from this primary voltage transformer is continuously monitored by the control electronics. In addition to serving other control functions, this signal is used by the control electronics to protect the equipment on the locomotive by tripping off the VCB in case of catenary voltage going out of limits. The main transformer is a specially built high impedance transformer as compared to those used in conventional locomotives. In addition to the primary winding, there are four traction windings and one auxiliary winding. A harmonic filter winding is also provided which has a filter connected across it to reduce the harmonics. In case of WAP5 loco, one hotel load winding is additionally provided. Each group of two traction windings feed two 4-quadrant line converters (12/1 & 12/2) connected in parallel. The line converters feed an intermediate circuit (known as DC link) consisting of a series resonant circuit (15.3, 15.4) and DC link capacitors (15.5), which supply power to the drive converter (12/3 + 13/1). The drive converter feeds two traction motors of a bogie in case of WAP5 and three traction motors of a bogie in case of WAG9. The traction motors are instantaneously discharged through the MUB resistor. Firing of the GTOs is controlled by the control electronics. During regenerative braking, the traction motors are made to act as induction generators by controlling the output frequency to obtain a negative slip value. In the line converter, the resultant 3-phase electrical energy is converted into single-phase energy through the DC link and is fed back to the catenary via the main transformer. The fundamental reactive power flow can be adapted to the line voltage conditions independent of the active power flow, thanks to the 4-quadrant pulse controlled converter. Thus the converter also serves to stabilize the line voltage. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 35 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 36 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 37  SALIENT DATA OF MAJOR SUBSYSTEMS OF WAP 5 LOCOMOTIVE EQUIPMENT, TYPE, MAKE AND MAIN RATING / DATA 1.1 Traction motor : Make : ABB Switzerland 4 Nos/loco Type : 6 FXA 7059 Cont. Max. Voltage phase to phase 2180 2180 V Current per phase 370 593 A Frequency 80 160.3 Hz Output at shaft 1150 1150 Kw Torque at shaft 6930 9920 Nm. Speed 1585 3174 rpm. Cos phi 0.86 All the above values are given for half worn wheels Design Speed 3571 rpm Over speed test speed 3571 rpm Stator winding Class 200, Veridur (R) system Insulation system 1.2 Transformer: Make : ABB, Switzerland 1 no / loco Type : LOT 7500 Rating : at 25 kV line voltage Primary winding 25 kV, 7475 kVA, 299 A Traction winding 4x1269V, 4x1449 kVA, 4x1142 A Aux. Converter winding 1000V, 334 kVA, 334 A Hotel load winding 750 V, 945 kVA, 1260 A Filter winding 1154 V, 400 kVA, 347 A No load current 0.5A at 22.5 kV Series resonant circuit 2x984 Arms,2x0.551 mH, Assembled in reactor linear upto 2x1391A peak transformer Cooling system Forced oil cooling Oil type shell using standard Diala DX mineral oil Impedances Traction winding ex = 59.4% (Guaranteed value for er = 3.08 % traction winding inductivity L = 2.1 mH + 15% only, others for information R = 34 m purpose) Aux. Converter winding TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 38  ex = 6.68 % er = 1.01% L = 0.5 mH R = 23.7 m Hotel load winding ex = 19.52 % er = 1.85 % L = 0.37 m R = 11 m Temp. Rises Primary 11 K Traction 17 K Aux. Converter 12 K Hotel load 13 K Filter 3K Temperature Cu. max. 100 C Oil max. 84 C Oil mean 82 C 1.3 Power converter: Make : ABB, Switzerland 2 Nos./ loco Type : UW 2423 – 2810 (i) 4 Quadrant power converter Suitable for Transformer secondary 2 x 1269 V at 25 kV line voltage voltage Frequency 50 Hz + 3% DC link voltage 2800 V nominal Cooling system Forced oil cooling Oil type shell using standard Diala DX mineral oil. (With 8 GTO Thyristors 4.5 kV / 3kA, Toshiba Type SG 3000 GXH 24 or equivalent type and gate units and 8 power Diode type D921S45T Eupec Make or equivalent) (ii) Motor Inverter Suitable for Motor voltage 2180 V (phase to phase) Motor frequency 0…160.3 Hz DC link voltage 2800 V (nominal) Cooling system Forced oil cooling Oil type shell mineral oil. Diala D TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 39  (With 6 GTO Thyristors 4.5 kV / 3kA, Toshiba Type SG 3000GXH24 or equivalent type and gate units and 6 Power Diode Type D921S45T Eupec Make or equivalent) (iii) DC Link Capacitor Make : Condis Type : CDM15230A0815 Rating : Capacity : 815 µF : Voltage :2940 Vnom Bank : 11.41 mF Capacity (iv) Instant Voltage Limitation Make : Microelettrica Scientifica, Italy Type : MUB Voltage : 2800 V Current : 500 A Containing - GTO thyristor and gate units - power diode - power resistor (Microelecttrica) (With 1 GTO Thyristors 4.5 kV / 3kA, Toshiba Type SG 3000 GXH 24 or equivalent type and gate units and power Diode type D921S45T Eupec Make or equivalent) (v) Series Resonant Circuit Capacitor Make : ERO Type : ERO – GFP 3.8 Rating : 560 µF, 2940 V Bank : 4.6 mF (The bank has 8 nos of Capacity these capacitors and one adjustable capacitor unit consists of 3 capacitors (280 µF+140µF+140 µF) TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 40 SALIENT DATA OF MAJOR SUBSYSTEMS OF WAG9 LOCOMOTIVE EQUIPMENT, TYPE, MAKE AND MAIN RATING / DATA 1.1 Traction motor : Make : ABB Switzerland 6 Nos/loco Type : 6 FRA 6068 3-phase Induction Motor Axle hung nose suspended type Cont. Max. Voltage phase to phase 2180 2180 V Current per phase 270 393 A Frequency 65 132 Hz Output at shaft 850 850 Kw Torque at shaft 6330 9200 Nm. Speed 1283 2584 rpm. Cos phi 0.88 All the above values are given for half worn wheels Design Speed 2842 rpm Over speed test speed 3250 rpm for 2 minutes Stator winding Class 200, Veridur (R) system Insulation system 1.2 Transformer: Make : ABB, Switzerland 1 no / loco Type : LOT 6500 Rating : at 25 kV line voltage Primary winding 25 kV, 6531 kVA, 261.25 A Traction winding 4x1269V, 4x1449 kVA, 4x1142 A Aux. Converter winding 1000V, 334 kVA, 334 A Filter winding 1154 V, 400 kVA, 347 A No load current 0.5A at 22.5 kV Series resonant circuit 2x984 Arms, 2x0.551 mH, Assembled in reactor linear upto 2x1391A peak transformer Cooling system Forced oil cooling Oil type shell using standard Diala DX mineral oil Impedances Traction winding ex = 59.4% (Guaranteed value for er = 3.08 % traction winding inductivity L = 2.1 mH + 15% only, others for information R = 34 m purpose.) TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 41  Aux. Converter winding ex = 6.68 % er = 1.01% L = 0.5 mH R = 23.7 m Temp. Rises Primary 11 K Traction 17 K Aux. Converter 12 K Hotel load 13 K Filter 3K Temperature Cu. max. 100C Oil max. 84C Oil mean 82C 1.3 Power converter: (Similar to WAP5 locomotive) TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 42  4. POWER CONVERTER INTRODUCTION The three phase voltage required for operating the traction motors is generated on the vehicle by means of two traction converters connected between the vehicle‟s main transformer (single phase) and the traction motors. To control the tractive or braking effort, and hence the speed of the vehicle, both the frequency and the amplitude of the three-phase converter output voltage are continuously changed according to the demands from the driver‟s cab. This allows continuous adjustment of the driving or braking torque of the traction motors, which means that the driving speed changes smoothly. When braking electrically the traction motors act as generators. In the converter the resulting three-phase electrical energy is converted into single-phase energy, which is fed back into the line (regenerative brake). OVERVIEW: STRUCTURE AND COMPONENTS OF THE CONVERTER. (See Fig.4.1) Line converter A11, A12…………… Oil – cooled value sets with 2 pairs of arms each, 2xZV24(12) A111 – A114 A121 – A124………. Gate Units (Forced air – cooling) (227) K01…………………Charging contactor (12.3) K11…………………Converter contactor (12.4) R04…………………Charging resistor (14) U11-U14……………Current transducers (18.2) TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 43 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 44 DC –Link A31………….DC – link capacitor bank (15.5) A33………….Series resonant circuit capacitor bank (part of the converter block) (15.4) H08………….Voltage indicator (15.7) L02………….Series resonant choke (15.3) (outside of the converter block) Q21………….Earthing switch (15.82) R51, R52…….Earthing resistors (90.61/90.62) R71………….Over voltage limitation resistor (15.1) U01, U02……Voltage transducers (measurement of DC-link voltage) (15.6) U05………….Earth fault monitoring voltage transducer (89.4) Motor Converter A21…………Oil-cooled valve set with 2 pairs of arms ZV24(12) A22…………Oil-cooled valve set with 1 arm ZV24 for the motor converter and 1 arm MU23 for the MUB (13) A211- A214 A21-A222……Gate units for the motor converter (228) A223…………Gate units for the MUB-arm (229) U21-U23……..Current transducers (18.5) Additional converter apparatus A01………..Converter bus station with converter control unit, SLG and drive control unit, ALG (415) A04………..Primary voltage transformer module (224) A08………..Gate unit power supply GUSP (219) ABBREVIATIONS The abbreviations used in these operating instructions are explained below: ALG : Drive control unit ASR : Motor converter BUR : Auxiliary converter FLG : Vehicle control unit GU : Gate unit GUSET : Gate unit transmitter / receiver test unit GUSP : Gate unit power supply MUB : Over voltage protection circuitry NSR : Line converter SLG : Converter control unit SR : Converter Ud : DC-link voltage VS : Valve set TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 45 ZK : DC-link ZP : Pair of arms MAIN CONSTITUENT PARTS AND THEIR FUNCTIONS (See main circuit diagram Fig.4.1) The traction converter is largely a modular construction and consists of the following main functional groups:  Line converter  DC – Link  Over voltage limitation circuitry  Motor converter Line converter (NSR) (A11, A12, A111-A124) (See main circuit diagram Fig.4.1) Circuit & Function The line converter consists of two pulse – controlled single – phase full bridge circuits (A11, A12) which are connected to a transformer secondary winding (terminals 1U1, 1V1 resp. 2U1, 2V1). The line converter is a self-commutating 4-quadrant converter. The AC terminals of the two bridge circuits (A11, A12) see AC voltages that consist of square–wave pulses of identical amplitude (see fig.4.2). These pulses are produced by pulse– width –modulating the DC–link voltage. The fundamentals of these alternating voltages are at line frequency and form the counter-e.m.f to the two transformer secondary voltages. The converter input current is in quadrature with EL i.e., voltage across transformer reactor. Since Es is equal to Vector sum of EL & EC (see fig. 4.3), it is possible to ensure that IS is in phase with ES by changing amplitude and phase of EC It could be seen that fundamental component of EC is nothing but modulating wave itself. Its amplitudes and phase angle, referring to the transformer primary voltage, can be changed independently of each other. This allows the adjustment at cos = 1 in either driving or braking mode. The full-bridge circuit GTOs are switched at a frequency much greater than the line frequency. The switching signals for the four pairs of arms are shifted by 90 (quarter of a switching period) in relation to one another. This ensures that the AC current in the transformer primary winding is almost sinusoidal and that the harmonic currents in the line are kept down to a minimum (for the whole converter operating range). The line converter maintains the DC –link voltage at a value, which is dependent on the power, direction of energy flow and line voltage. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 46 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 47 Main constituents parts The two converter bridges A11-A12 each consist of two bipolar switches. Two GTO – thyristors arms and two diodes, connected in anti – parallel, realize each bipolar switch. These two pairs of arms together with their snubber circuit components are housed in a square aluminium tank and form a so-called valve set (A11 and A12). Such a valve set is oil – filled and cooled by forced oil circulation. The four gate units do not belong to the valve set. They are, however, placed in their immediate vicinity. The line converter input currents are measured by means of the current transducers U11, U12 resp. U13, U14. Their output signals are sent to the converter controller in the drive control unit (ALG). DC-link (L02-A33, Q21, R51-R52, U05, U01-U02, Ho8, A31, R71-A22) (See main circuit diagram Fig.4.1) Function The DC-link connects the line converter to the motor converter. Primarily, it serves to compensate both periodic and non-periodic power differences between the motor-side and line-side terminals of the traction converter. Such power differences occur on the one hand as relatively low frequency pulsations caused by the single-phase circuit of the line converter. On the other hand they may occur as irregular transient surges produced by sudden disturbances of the power equilibrium between the motor side and line-side of the converter, e.g. due to pantograph bounce, wheel spin etc. It is not possible to completely avoid these transient power differences but they can be minimized. It is a characteristic of the circuit that the power equilibrium after a disturbance cannot be instantaneously recovered, there is a certain delay. Absorption circuit (A33-LO2) The periodic pulsation in the DC-link occurs because the fundamentals power in a symmetrically loaded three-phase system (traction motor system) is constant, whereas the fundamental power in a single-phase system pulsates at double the line frequency. Referring to the DC-link currents of the converter, this means that the DC-link is fed from the line converter with a pulsating current at double the line frequency, whereas the motor converter draws almost pure DC-current from the DC-link. The A33-L02 series resonant circuit serves to filter out the current at double the line frequency. It must therefore be tuned to this frequency. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 48 DC-link capacitor (ZK) (A31) The DC-link capacitor is used to cater to non-periodic power differences between the motor and line sides of the converter. It also absorbs the harmonic currents produced by both the line converter and the motor converter (frequency higher than double the line frequency). The DC-link capacitance is rated in such a way that the DC-link voltage remains as constant as far as possible under all operating conditions and that there are no inadmissible fluctuations with regard to the operation of the motor converter. Over voltage limitation circuit MUB (R71-A22) If the capacitance of A31 is not sufficient to prevent the DC-link from sudden and inadmissible high transient overvoltages the R71 overvoltage limitation resistor is almost immediately connected across the DC-link by the firing of a GTO in the A22 valve set. The GTO is fired as soon as a certain overvoltage threshold is reached. After the overvoltage has decayed, the GTO is turned OFF again. Overvoltages in the DC-link may occur due to:  Wheel spin  Pantograph bounces  Detuned (defective) series resonant circuit (L02, A33) The MUB-circuit also serves to discharge the converter DC-link if the vehicle is put out of operation (powering-down). Valve of the MUB-resistor is 2.5 m. The temperature of the MUB-resistor is monitored in the control electronics by a thermal model. Furthermore, the DC-link also contains the following measuring, monitoring and protective functions:  DC-voltage measurement, transducer U01, U02 for converter control  Voltage indicator H08 and converter earthing switch Q21  Earth fault monitoring system (U05, R51 + R52) Motor converter (ASR) (A21, A22, A211-A222) Function The motor converter consists of a pulse-controlled three-phase bridge circuit (valve set A21, A22), which is connected to the DC-link. On the AC-side, it is connected to the three motor stator windings (connected in start). All 2 resp. 3 motors are connected in parallel. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 49  Each of the three pairs of arms of the three-phase bridge circuit (two of them in A21, one in A22) generates an AC-voltage from the DC-link voltage. This AC-voltage consists of square pulses of constant amplitude. Both the fundamental frequency and the amplitude of the alternating voltage can be changed continuously and independent of each other. These 3 voltages appear at the converter output terminals 1U2, 1V2, and 1W2. Their fundamentals are shifted against each other b by 1/3 period (120°) and from the phase voltages of the traction motor three-phase system. The torque and the speed of the motors are controlled by continuously changing both the frequency and the amplitude of the fundamentals of the pulse-shaped motor-phase voltages. In motoring mode (driving mode) the fundamental frequency of the motor terminal voltage is higher than the frequency corresponding to the motor speed (positive slip), resulting in a positive motor torque. During braking, the fundamental frequency of the motor terminal voltage will be lowered below the frequency corresponding to the motor speed, resulting in a negative slip and therefore producing a braking torque. The whole control range of the motor voltage is subdivided into three smaller ranges i.e., (indirect self-control), TB_DSR (direct self control), or “tolerance band control” as well as square-wave operation or “field-weakening”-DSR, characterized as follows: ISR (indirect self control) The ISR-range covers the range from standstill (motor voltage = 0) up to approx. 30% of the nominal voltage and type frequency (resp. type speed) of the motors. In this range, the relationship between the motor voltage amplitude and frequency remains roughly constant. This is achieved using the pulse-width-modulation method. The motors are constantly magnetized at nominal induction and can be loaded with the nominal torque over the whole ISR-range. The GTO-switching frequency is constant over the whole ISR-range. Therefore, the motor voltage per half-wave consists of a variable number of pulses having the same amplitude but differing widths. TB-DSR (tolerance band control) The TB-DSR covers the range from approx. 30% up to 98% of the nominal voltage and nominal frequency (resp. nominal speed) of the motors. Over this range the motors are fully magnetized and therefore they can be loaded with the full torque (see Fig.4.4). TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 50  Fig. 4.4 The torque, however, is no longer controlled to an average value but to a set value. The difference between actual torque and set value must always lie within a preset tolerance band whose width is determined by the admissible GTO-switching frequency. Thus, the motor converter is always operated with the largest possible switching frequency, resulting in the smallest possible torque pulsations. “Field weakening”-DSR (square-wave operation) The “field weakening” range is the region between the nominal speed (nominal voltage) and the maximum speed of the traction motors. Over the whole field weakening range the amplitude of the motor voltage is kept at its maximum value. Only the frequency is changed. This has the effect that the motor flux and pullout torque are inversely proportional to the frequency. The line-line motor voltage in square-wave operation is formed by one voltage pulse per half-wave. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 51 TRACTION CONVERTER CONTROL BY THE CONTROL ELECTRONICS (See main circuit diagram Fig. 4.1) The traction converters serve to provide continuous and utmost automatic control of both speed and torque of the three-phase induction motors. The demands from the driver‟s cab, such as driving or braking, and the relevant driving speed are converted into the voltage, current and frequency values required on the traction motor side by means of the control electronics and the converter power electronics. The traction converters of a vehicle are exclusively controlled by the central vehicle control unit (FLG) and the individual converter control units (SLG) as well as the relevant drive control units (ALG). The converter has no hand-operated component except the earthing switch Q21. Basic structure of the control electronics The control electronics is fully based on microprocessors, connected to each other via a data bus system (MICAS vehicle bus). Each vehicle contains a vehicle control unit (FLG). Each converter is controlled by a converter bus station. The A01-converter bus station contains both the converter control unit (SLG) and the drive control unit (ALG), which is controlled by the former. Furthermore, the ALG is also equipped with controllers, one each for the line converter and the motor converter. Motor converter (ASR) control Depending on the demands made in the driver‟s cab and the instantaneous speed of the vehicle, the FLG calculates the required tractive or braking effort. The demanded torque is sent to converter bus station via the vehicle data bus. The SLG compares the demanded torque from the FLG with the effective load torque calculated in the ALG. The demanded torque for the ALG is determined from the difference between these two values. The ALG determines the required firing and turn-off pulses for the GTOs on the basis of the demanded torque. The pulses are sent to the gate-units (A211-A222) via fiber optics. The outputs of the gate-units are at high potential. The actual firing and turn-off pulses for the GTO-thyristors are only generated in the Gate Units (GU). The Gate Unit Power Supply A08 (GUSP) provides the Gate Units with the required energy. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 52 Line converter (NSR) control The line converter is also controlled by the ALG. The ALG controls the line converter in order to maintain a constant DC-link voltage. This DC-link voltage is reduced, if the needed power is below the rated value. Hence, the loading of the line converter has to correspond to the loading of the motor converter. Therefore the flow of active power on both sides of the traction converter is of the same value and direction (driving, braking). MONITORING OF GTO – Thyristers The GTO-thyristors are not only controlled by the drive control unit (SLG, ALG) and Gate Units but are also monitored (GTO feedback signals). This ensure for example that a GTO is only fired if the necessary conditions are fulfilled, and that the converter is immediately shut down (or not powered-up) when a GTO fails. Additional functions performed by the vehicle control unit, converter control unit and drive control unit (FLG, SLG, ALG) Apart from the control functions described above, the vehicle control unit and the converter control units fulfill numerous additional functions. The following functions are important for the converter:  Automatic powering-up and powering-down of both the vehicle and the converter according to the selections from the driver‟s cab.  Monitoring of various variables (limit values). TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 53 AUTOMATIC SYSTEM TESTS The converter is regularly and automatically tested by the control electronics. This takes place when the vehicle is first powered-up and whenever the converter is powered-up again, e.g. after a protective shut-down during driving mode. The functional test consists of two parts, the OFF-LINE TEST and the ON-LINE TEST. The OFF-LINE test is performed before any turn-ON (the converter being de- energies). The ON-LINE test, however, is carried out during the charging of the DC- link as well as during the operation. OFF-LINE TEST The OFF-LINE TEST tests the following functions (amongst others):  The current transducers (U11-U23) by means of simulated actual value signals (test windings).  The comparators for the various protection thresholds.  The power supplies for the gate units and the control electronics. ON LINE TEST The ON-LINE TEST tests the following functions (amongst others):  That the K01 charging contactor closes.  That the DC-link voltage is reached within a predetermined time.  That the K11 main contactor closes.  That the actual value signals of the voltage transducers (U01, U02) are correct (plausibility test).  That the MUB is ready for operation. During operation, different states and values, which allow the release of the GTO firing pulses, are continuously (ON-LINE) monitored. Amongst others they are  The position of the vehicle main circuit breaker, the K01 charging contactor and the K11 main contactor.  The pressure and the temperature in the oil cooling system.  The converter DC-link voltage.  The current and voltage transducers (plausibility test).  The gate unit supply voltages. The ON-LINE test is only initiated when the OFF-LINE test is successfully complete. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 54 CONVERTER TURN-ON/OFF (So called powering-up and powering-down) Powering-up (See main circuit diagram Fig.4.1) When powering-up the vehicle, the converter is powered-up after the OFF-LINE test. For this purpose the K01 charging contactor is closed, so that the converter DC-link is precharged through the R04 charging resistor and the diodes in the A11 valve set. Immediately afterwards the K11 main contactor is closed. Subsequently, the GTO-thyristors‟ control pulses for the line converter are released and approx. 200 ms later those for the ASR (motor converter). The conditions for control pulse release are:  Closed vehicle main circuit breaker.  Converter powered-up (i.e., OFF-LINE and ON-LINE test OK).  Gate unit supply (GUSP) OK.  Driving direction switch (reversing switch) set to “forward” or “reverse”.  DC-link charged. Powering-down The converter is powered down if:  The vehicle is put out of operation.  The converter protection (steps 4 or 5) has reacted.  The line voltage is too low for a considerable time. When powering-down  The demanded torque is reduced to zero.  The firing pulses of both the line and motor converter are inhibited.  Main circuit breaker is opened.  The K11 main contactor is opened, and  The MUB is turned ON (DC-link is discharged). CONVERTER PROTECTION (See main circuit diagram Fig.4.1) Various conditions during converter operation (wheel spin, pantograph bounces, overload) as well as errors in the control electronics may endanger important components of the converter, especially the power GTOs. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 55  In order to prevent this and to affect the converter normal operation as little as possible a five-stage protection concept is used, whose individual stages are described below. Protection stages Protection stage 1: Monitoring of the minimum switching times of the GTO- thyristors and mutual interlocking of the gate units of a GTO-thyristor pair of arms: To ensure the safe function of the converter, when it is alternately switching the plus or minus pole of the converter DC-link to the relevant converter terminals (alternate firing and turning OFF of the GTO-thyristors in a ZP), it is absolutely necessary that minimum turn ON and OFF times are observed including the minimum change-over time of the GTO- thyristors. These times are monitored by the control electronics. A further step to avoid shorting the DC-link is to interlock the firing signals for the two GTO-thyristors of a pair of arms. A firing command is only released if the neighbouring GTO has safely turned off. Triggering: Protection stage 1 responds as soon as the converter reaches its control limits. Effect on the operation: Normal operation is maintained. The diagnostic system will indicate a fault. Protection stage 2: Power and current set value limitation: In order to prevent the converter from thermal overloading, it is important that certain current limits on both the line side and motor side are not exceeded. For this reason, the current and torque set values required by the converter control circuits are limited. Triggering: Protection stage 2 responds either if the overhead line has under voltage or if the motor converter is operated with motor fundamental frequencies that are below 1.1 Hz. Effects on the operation : TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 56  Reduction of the motor torque. No fault is indicated. Protection stage 3: Instantaneous voltage limitation MUB : Normal operation is transiently affected but maintained. No fault is indicated. Protection stage 4: Full reduction of load : (Controlled reduction of the motor torque to zero) To reduce the power flow in the converter as quickly as possible, but without disturbing the power equilibrium between line and motor converter (otherwise there is a danger of overvoltages in the DC-link), the torque of the driving motors is quickly and continuously reduced to zero (ramp function). Subsequently, all the GTO-thyristors of both the line and motor converters are turned off. Triggering: Protection stage 4 responds if:  The plausibility test of the current and voltage transducers indicates a fault (either thermal drifts or defective transducer).  The MUB – resistor overheats.  Either the cooling medium temperature is too high or the inlet pressure is too low.  The converter control circuits attain an abnormal state (e.g. a GTO-thyristor can not be fired). Effects on the operation: The converter is turned off and turned on again, provided it has passed the off-line test. If the test, however, is not successful, the converter will automatically be powered down, which means that it is completely shut down. The DC-link will be discharged. Protection stage 5: Immediate converter shut-down: (Opening the vehicle main circuit breaker and firing the MUB) The converter is fully shut down without delay. For this purpose the MUBs are fired by means of a continuous pulse, all the GTO-thyristors of both line and motor converter are turned off and the vehicle main circuit breaker is opened. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 57  Triggering: Protection stage 5 responds, if:  The maximum admissible DC-link voltage is exceeded despite activation of the MUB (protection stage 3).  The MUB (protection stage 3) responds several times in a row.  The maximum admissible current is exceeded at one of the power terminals of the converter.  The gate units of a pair of arms signal either an inadmissible switching state or a defective GTO-thyristor.  The DC-link voltage inexplicably drops below its minimum admissible value.  Either the gate unit power supply or the supply for the control electronics fails Effect on the operation After vehicle shut-down the converter undergoes an OFF-LINE test. It the test is not successful, it remain shut shown. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 58 Behavior in case of line under voltage during operation If during operation the line voltage drops below the minimum allowable value. The motor converter and then immediately afterwards, the line converter are turned off (or vice versa depending if the converter is in motoring or braking mode). In the blocked state, the DC-link voltage gradually drops. If the line voltage returns inside the tolerance range before the DC- link voltage has decreased too much, the firing pulses are again released. If however the line voltage remain below the minimum value for more than approximate10 seconds, the converter will be powered down. Once the line voltage has recovered, the normal powering- up process will be initiated. Fig. 4.5 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 59  5. AUXILIARY CIRCUIT DESCRIPTION The auxiliary circuit in WAP5 and WAG9 locomotives has single phase as well as 3-phase auxiliary motors. The circuits feeding the single phase machines and 3-phase machines are distinctly separated although they are fed from one and the same auxiliary winding (1000V) of the main transformer. SINGLE PHASE CIRCUIT The single phase auxiliary circuit is shown in Fig.5.1. An auxiliary transformer to give 415V and 110V AC output steps down the auxiliary winding voltage. The following loads are connected in the 415V AC circuit:  Machine room blowers.  Scavenge blowers for machine room blowers.  Cab heaters. Loads connected to the 10V AC circuit are:  Cab fans.  Blowers for cab heater. The 415V and 110V AC auxiliary circuits energized as soon ad VCB is closed. The machine room blowers cool different electronic cubicles in the locomotive in addition to provide for pressurisation of the machine room. For working control electronics a machine room temperature below 70°C is to be ensured. In peak summer periods, if the locomotive with all the doors and window closed is kept under the sun for a long time, there is a possibility that the machine room temperature exceeding 70°C. Provision of a “cooling mode” operation in the control circuit facilitates raising of pantograph and closing of VCB in such an eventually without intervention of control electronic. The machine room blower starts working to bring down the machine room temperature after which the locomotive can be operated in the normal “driving mode”. 3-PHASE CIRCUIT The overview of the 3-phase auxiliary circuit is shown in Fig.5.2 for running the 3-phase auxiliary motors, WAP5 and WAG9 locomotives are equipped with 3-phase static auxiliary converters to supply the auxiliary machines of the locomotive. The static auxiliary converter is very different in principle, construction and operation from the conventional Arno Converter. Since there are no rotating parts as in the Arno Converters, these converters have less wear and tear, thus making it almost maintenance free. CIRCUIT DESCRIPTION The load distribution among the BURs is such that required redundancy is achieved by automatically switching load from one auxiliary converter to another in case of failure of any TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 60 one auxiliary converter. BUR1&2 feed variable voltage and variable frequency supply to the traction motor bowers; oil cooler blowers and its scavenger blower of bogie1 & bogie2 respectively. BUR3 feeds a fixed frequency supply to the two compressor motors and two converter and transformer oil pumps. In addition to that, BUR3 also feeds the battery charger. For traction motor blowers, oil cooler blowers and their scavenge blowers, the speed is controlled in three steps (17Hz, 33Hz & 50Hz) by the control electronics depending on the temperature of the traction motors / cooling oil sensed by temperature sensors in traction stator and in oil cooling circuit. BUR3, on the other hand, is operated at a fixed frequency of 50Hz to feed the drive motors of the main compressors, oil pumps in addition to the battery charger. The output voltage of Bur3 varies a little around 415V depending on the battery charging requirement. However, whenever a compressor starts, the output voltage and frequency of BUR3 are reduced to near zero and then ramped upto the full values to achieve a soft start of the compressors. Load changeover from one auxiliary converter to another in case of isolation of any one auxiliary converter to another in case of isolation of any one auxiliary converter is done automatically by the auxiliary converter electronics with the aid of electro-pneumatic contactors. If BUR1 fails and gets isolated, BUR2 feeds the auxiliaries for ventilation of both the bogies up to a maximum frequency limited to 42Hz. If BUR2 fails & gets isolated, BUR1 feeds the auxiliaries for ventilation of both the bogies up to a maximum frequency limited to 42Hz. If BUR3 fails and isolated, BUR2 feeds the compressor motor, oil pumps and the battery charger at affixed frequency of 50 Hz and BUR1 feeds the auxiliaries for ventilation of both the bogies up to a maximum frequency limited to 42 Hz. As shown in Fig.2, under normal operation, contactors 52/1, 52/3 52. ½, 52/5 are closed and contactors 52/2, 52/4, 52.1/1 are open. When BUR1 is isolated, contactors 52/4, 52/1, 52/3 and 52.1/2 are closed and 52/5, 52/2 and 52.1/1 are open. When BUR2 is isolated, contactors 52/5, 52/4, 52/3 and 52.1/2 are closed and 52/1, 52/2 & 52.1/1 are open. When BUR3 isolated, contactors 52/2, 52/4, 52/5 & 52.1/1 are closed and 52/1, 52/3 & 52.1/2 are open. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 61  Fig. 5.1 Single Phase Auxiliary Circuit TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 62  Fig. 5.2 Overview of Three Phase Auxiliary Circuit TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 63  6. AUXILIARY CONVERTER 1.0 INTRODUCTION Each locomotive is equipped with two boxes enclosing the static auxiliary converter system. 1. BOX1 containing BUR1 2. BOX2 containing BUR2 & BUR3 and battery charger, which may be, fed from one of the two converters and which may be considered to be a functional part of the converter system. Fig.6.1 shows the converter function within the locomotive and Fig 6.2 the essential parts of the auxiliary converter and battery charger. Three auxiliary converters are designed for connection to the auxiliary services winding of the main transformer. Each converter is rated for 100 KVA output and has short circuit proof three-phase output at 415 V. The output frequency of converter BUR1 & BUR2 is variable from 0 to 50 Hz while BUR3 gives fixed frequency output at 50 Hz. The battery charger is supplied from the converter BUR3. In case of the fault in the converter, BUR2 will feed the battery charger. The battery charger with a rated output of approx. 111 V charges the locomotive batteries and supplies the low voltage loads. The low voltage output is electrically insulated from the input and from the three-phase output. The converters are provided with external forced convection cooling (5 m/sec approximately). Thermostats are provided inside the box. When the temperature goes above 50C, fans run until temperature decrease below 35C. Both boxes and three phase output chokes are mounted in the machine room of the locomotive. The intermediate chokes are incorporated in the main transformer tank for convenience and in order to save weight. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 64  Fig. 6.1 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 65  TECHNICAL DATA Input Supply voltage : 1000 V AC +200 V -300 V Apparent power : 100 KVA Current (r.m.s.) : 150 A (100 KVA and 700 V) Frequency : 50Hz + 3% Rated insulation voltage : 1200 V Test voltage (50Hz/60 sec) : 4250 V Intermediate circuit Voltage : 550 VDC Rated current : 155 ADC Short term overload : 190 ADC Rated insulation voltage : 900 V (capacitor) Test voltage (50 Hz/60 sec) : 2600 V TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 66  Fig. 6.2 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 67 2.3 Output AC DC Rated voltage (fundamental r.m.s) : 415 V --- (DC voltage) : --- 111 V Rated frequency (BUR1 & 2 ) : 50 Hz --- (BUR3) : 50 Hz --- Rate current (AC includes battery charger) : 140 A --- Max. battery charger current (only battery) : --- 80 A (user + battery) : --- 110 A No. Of poles (conductors) : 3 3 Rated insulation voltage : 900 V 150 V Test voltage (50 Hz/60 sec) : 2600 V 1500 V 2.4 Control unit Supply voltage: 77..137.5 V (operating range) Power consumption : 120 W 2.5 Thermal losses and cooling by forced air Thermal losses at rated power Box1 : 2 KW Box2 : 5 KW Ventilator supply voltage : 36….56 V Ventilator power losses : 5W Air rate : 5 m/sec TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 68  Fig. 6.5 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 69  3.0 CIRCUIT DESCRIPTION The main parts of the converter are:  The half controlled rectifier bridge [50.11]  The intermediate filter (inductor [51.3] and capacitor [51.1])  Three inverter legs, connected as three-phase inverter [50.12]  The electronic control unit  The three phase output inductor [50.9]  The battery charger (three phase transformer [107.1] and rectifier ) The other components serve to detect the actual values required to control the process and to ensure that the necessary operating condition are maintained for reliable operation of the power electronics. 3.1 Rectifier The half controlled asymmetrical type GTO rectifier is used. The rectifier converts AC to DC and maintains output dc voltage of approx. 550 V. The input & output voltage waveforms are shown in fig.6.3 and currents through devices are summarized in fig.6.7. Average value of rectifier output voltage: √2 U2 = --------- x Un rms x (1 + cos )  The active power transmitted through the converter amounts to P = UZ x IZ, IZ being the average value of the link filter current. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 70  Fig. 6.6 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 71 3.2 DC link filter DC link filter consists of intermediate circuit reactor and capacitor. The intermediate circuit reactor smoothes the pulsating energy flow from the input rectifier and supplies DC current (IZ) with superposed ripple. The choke is equipped with two coils in order to keep voltage spikes away from the inverter and the connected load. The intermediate circuit capacitor (CZ) absorbs the component of the current, with little fluctuation in terminal voltage. In addition, CZ represents the low impedance voltage source, essential for functioning of three phase inverter. CZ also supplies the magnetization current to the inductive load. The intermediate circuit capacitor consists of 2-stage series circuit of 6 parallel-connected electrolytic capacitors each. The voltage across the series connected stage is balanced with resistors. These are dimensioned so that the current passing through them is several times larger than the capacitor leakage current and they thereby determine the voltage sharing. At the same time they act as discharge resistors. Fig.(4) shows the voltage waveforms across the filter input and output. 3.3 Three phase inverter The three-phase inverter consists of three single-phase inverter modules. They generate a three phase AC voltage from the intermediate circuit DC voltage by being approximately switched ON and OFF Fig.5 shows the switching sequences of the three modules is steady state conditions. The rectangular output voltage of inverter may be represented as an infinite sum of sine waves as follows: U(t) = UZ x [(√6 x √2 ) / ( x n)] x  sin ( n x 2 f1 x t ) TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 72  Fig. 6.7 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 73  With f1 = inverter frequency as understood conventionally fundamental component and n being 1,5,7,11,13,17….( = 6k ±1, k = 1,2,3,4……) The shaft power of motor is function of fundamental component √ 2 U1rms = UZ x ------  In case of resistive loads, the heating will be function of total rms value. V (total) rms = UZ x √ 2/3 In steady state operating conditions, both frequency and amplitude of output voltage correspond to set point, while in dynamic conditions these values can be set away from the reference value by PWM for better control of the process. 3.4 Three phase inductors The inductor slightly attenuates harmonics but mainly provides the converter with the required capability of withstanding load short – circuits. 3.5 Battery Charger The diode bridge (107) rectifies the voltage supplied from one of the auxiliary inverter through 107.1 A capacitor of 2.2 mF located on 107 smoothes the charger voltage and limits the transient voltage rise when some major load is switched off. The current transducers 107.2 and 107.3 transmit the actual current values to the control unit of inverter BUR2 while the transducers located on the charger module transmit the same values to inverter BUR3 (normally supplying the battery charger) control unit (Ref. Fig. 6.8). TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 74  Fig. 6.8 TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 75 3.6 Protective devices I. Battery charger circuit breaker – The battery charger is protected against overload by magnetic circuit breaker 100. the breaker isolates the battery charger from the inverter output through magnetic tripping in case of short circuits inside the battery charger. The converter need not be switched off and locomotive can continue to run until the battery capacity is exhausted. II. Input fuse – The fuse protects from serious consequential damage, which result in the event of failure of power components in the rectifier bridge or defects of the regulation or the actual value monitoring. III. Surge arresters [40.1] – The surge arresters protect the semiconductors of the rectifier bridge [50.11] from over voltage spikes. IV. Damping filter RC [49.2/49.1] – The small filter is intended to limit the rate of rise of voltage spikes in order to avoid spurious thyristor firing. 3.7 Measurement devices I. Input voltage measuring transformer. It provides the electronic control unit with information about amplitude and phase of input. II. Voltage transducer. It is used to measure intermediate circuit voltage. 3.8 Auxiliary Converter control unit It handles all control and electronic protection functions. The control unit communicates with the vehicle control unit (FLG) via MVB optical bus. The rack contains:  A power pack with electrical insulation between input and outputs, which converts the battery voltage varying over a wide range into the various stabilized voltages e.g. +24 V for gate unit supply, +15 V for analog circuit and transducer supply and +5 V for digital circuit. All voltages have a common ground.  The microprocessors unit including binary input / output card. This unit provides the regulation of the link voltage (i.e., it controls the input rectifier) and of the battery voltage. It is in charge of the higher-level protective functions, of the contactor control and of the communication with the FLG.  The bus interface board converting the electrical signals elaborated by the microprocessor unit into the optical ones and vice-versa. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 76  7. CONTROL ELECTRONICS & VEHICLE DIAGNOSTIC SYSTEM The Control electronics used in WAP5 and WAG9 locomotives is known as MICAS–S2 (Micro Computer Automation System Series 2). MICAS–S2 is a process oriented, distributed control system optimized for the application on electric traction vehicles. It consists of a number of devices for signal input / output, signal processing and communication systems to exchange data between bus stations (control units). A man- machine interface for the operating system as well as aids for planning, commissioning and maintenance of an installation is also provided. FIELD OF APPLICATION The MICAS-S2 control system is mainly used in electric traction vehicles, such as locomotives, multiple unit trains, tramways and trolley buses. A modern transportation system has high demands on the vehicles. Thanks to its modularity, MICAS-S2 can be adapted to the various requirements. There are three hierarchical levels in the MICAS traction control system (Fig.7.1) train control, vehicle control and drive control level. The train control level coordinates and controls coordination of several similar traction vehicles (multiple traction), interfacing to brake systems and much more. It is the train control level that converts the driver‟s commands (e.g. set speed) into commands for the individual vehicles. These commands are passed on to the vehicle control level for execution. The vehicle control level is responsible for all the vehicle functions. It converts the commands of both the train control level and the driver into actions (contactor control, EP- valves etc) and gives feedback about important events or operating states. To allow the driver to concentrate on his most important task, i.e. observing the track and signals, the vehicle control level automatically reacts as far possible on all events occurring during operation. The third hierarchical level is the drive control level. It receives the set value of the tractive effort required from the vehicle control level and controls the power converters in such a way that the motors will deliver the required torque. MICAS-S2 comprises components for all the three hierarchical levels. Thus all requirements demanded for modern vehicle can be met such as: * Full integration of all control system tasks for a train. - Measuring and conditioning of process values. - Control of all functions. - Drive control. - Power supply. - Data exchange between sub-systems of a vehicle and between several vehicles. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 77  - Supervision on inadmissible operating condition. - Protection of components and vehicles. * Integrated diagnosis to support both operation and maintenance. * Safe operation (inherent or user configurable redundancy of the control system) * Easy vehicle maintenance due to high modularity and availability of components. * Efficient vehicle production with extensive test of preassembled modules before integration in the vehicles. *Possibility to adapt to changing needs during the whole life time. CHARACTERISTICS The MICAS–S2 control system takes charge of all tasks necessary for operating,, monitoring and maintaining vehicles. Furthermore, because of it structure and modes of operation it offers exceptional advantages for both the vehicle manufacturer and the customer.  Internationally standardized data transfer according to IEC TC9 WG22 (Train Communication Network, MICAS Vehicle Bus and Train Bus).  Self-diagnosis of all the devices with centralized processing and the degree of fault tolerance can be widely adapted to requirements regarding availability and safety.  Simple configuring and programming of an installation thanks to powerful and user-friendly software tools (Mic Tools).  Uniform interface between software and data transfer systems.  Access to all devices via MICAS vehicle Bus for commissioning and maintenance.  Integration of third-party systems (electronic modules of other manufacturers) into a MICAS-S2 installation.  Extensive protection against electromagnetic interferences. Communication is one of the most important functions of a distributed control system Requirements for data transfer between the control electronics component of a vehicle are quite different from the data exchange between different vehicles. Therefore MICAS-S2 includes various data transfer systems that offer optimum adaptations such as the Train Bus, the MICAS Vehicle Bus and the Parallel buses. Data between up to 62 vehicles can be exchanged by the Train Bus. It is possible to control one or several traction vehicles (multiple traction commuter train). The Train Bus flexibly adapts to any configuration alteration of a train. Mixed trains with vehicles having no interface to the Train control bus are possible. The MICAS Vehicle Bus is optimized for the transfer of real-time process values. The cyclic data transfer according to the broadcast principle allows a very efficient utilization of the transmission capacity available. Cycle times between 1 ms and 1024 ms are possible. Upto 127 devices can be connected TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 78  to a bus. Considerable noise immunity is obtained by linking the modules with fibre optic cables. The Parallel bus (AMS-Bus) is used to control input/output devices in subracks. Another very important function of MICAS-S2 is the drive control electronics. Asynchronous motors mainly used in modern traction vehicles are very dynamically controlled due to the stator-flow-oriented torque control process (direct and indirect self control). This results in maximum adhesion utilization, optimum comfort and minimum wear. Traction vehicles equipped with MICAS-S2 drive control offer universal application both in pulling heavy goods trains or in front of fast passenger trains. HANDLING MICAS-S2 offers uniform user-friendly tools for the design, commissioning and maintenance staff. The Mic Tools package presents a wide variety of programs to fulfill most of their tasks. User programs for general control tasks are programmed in the process oriented Function Block Language (FUPLA). FUPLA is a programming tool using graphic symbols called function blocks. This makes it very simple to write, test and document programs for the automation of process. The shielded subracks, the protective circuits in the electronic modules as well as the shielded cables for analog process signals guarantee and optimum safety of operation even in very harsh environments close to strong sources of electromagnetic radiation. Internal signals and the supply voltages are wired via the rear rack connectors in wire wrapping technique and with back planes. For the remote bus of the MICAS Vehicle Bus and the signals to the power converters fibre cables with ST bayonet connectors are used. PROGRAMMING The Software required to use the MICAS-S2 control system can be divided into three groups.  Programs in the control system processors that are independent of the application (operating system firmware).  Programs for the project specific task of the control system (user programs for control tasks, diagnosis, visualization).  Programs for the planning of installations, i.e., to write the project specific software as well as for testing, commissioning and maintenance purposes (Mic Tools). TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 79  DIAGNOSIS CONCEPT As part of the distributed control system the MICAS-S2 diagnosis has a decentralized structure. The diagnostic messages are produced by the computers involved in the process and transmitted to the diagnostic computer. The later is equipped with an expert system which evaluates and stores the incoming messages. Special functional blocks in the Function Block Language (FUPLA) are intended to produce the diagnostic messages in the computers. Therefore the programmer can define which disturbances will cause a diagnostic message to be sent. The diagnostic messages of the different devices are evaluated by an expert system. The system processes the incoming messages by means of pre- defined rules considering the present operating state of the system. If a failure occurs the driver is given hints on a driver‟s cab display whether to maintain or to r