Three Phase Technology PDF

11.AC DC 3-phase EMUs Since inception, several technical inputs have been incorporated in EMU stocks which were air brake system, improved design of traction motors, Thyristors control, fluorescent lights and improved fans etc. These changes improved the reliability and performance of the EMU stocks...

11.AC DC 3-phase EMUs Since inception, several technical inputs have been incorporated in EMU stocks which were air brake system, improved design of traction motors, Thyristors control, fluorescent lights and improved fans etc. These changes improved the reliability and performance of the EMU stocks. However, the basic drive running the trains continued to utilize DC series motors. The presence of commutator and brushes impose severe limitations on the use and reliability of the traction motors. The main reason behind the use of DC traction motors has been its high starting torque and easy speed control. The ac induction motors were handicapped on account of absence of these characteristics. With the advent of modern power electronics technology, it is now possible to achieve high starting torque and better speed control with 3 phase AC induction motors and variable voltage variable frequency (VVVF) control. 3 phase EMUs offer remarkable benefits like energy saving, low maintenance cost, higher reliability etc. These EMUs can be used under both AC as well as DC traction, which will be beneficial in meeting the requirement for DC-AC conversion work, in suburban areas of Mumbai. THE ADVANTAGES OF 3-PHASE DRIVE WITH GTO THYRISTORS OVER THE CONVENTIONAL TECHNOLOGY ARE:  It enables energy efficiency  It provides stepless control thereby increasing passenger comfort.  Better adhesion between wheel and rail due to smooth control.  Due to digital electronic control the flexible operation wide range of diagnostic features and very compact size of equipments.  Robustness and reliability with a low maintenance requirement.  High power to weight ratio.  High voltage, low current operation.  Inherent regenerative braking capability.  Unity power factor in AC traction. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 120  SPECIAL FEATURES OF 3-PHASE AC-DC EMUs:  Use of GTO based traction converter and inverter with VVVF control for 3- phase traction motors.  Increase power with 3-phase induction motor of same size as existing DC motor – 240 kW as against 187 HP of DC EMU & 224HP of AC EMU.  Roller bearings axle suspension there by reducing maintenance requirement compared to DC motors with sleeve type axle suspension bearing, which calls for frequent maintenance. Also, the life of roller bearings is more than 3 times that of sleeve bearings and the operating performance is superior.  Coil suspension on existing rake and air suspension on bogie increasing riding comfort as well as better control of bogie parameters under varying load conditions.  Regenerative braking – 30 to 35% saving in energy in addition to reduction in wheel and brake shoe wear there by reducing maintenance requirement.  Auto sensing of OHE and selection of AC or DC mode.  All auxiliary machines working on 3-phase, 415 volts AC supply including drive motor for air compressor, which will reduce maintenance requirement.  PLC based control for traction and auxiliary circuits including protection which will be more reliable compared to the relay based system presently in use.  IGBT based Static battery charger.  The light and fans work on 141 volts AC as compared to 110 volts DC on the existing stock. AC fans are maintenance free compared to the DC fans which need frequent attention to carbon brushes. Introduction to solid state switching circuits: Reduction of system losses is one of the major achievements resulting from the use of solid – state power devices. As an example, the induction motor is known for its low efficiency at light loading conditions. To reduce its losses, the terminal voltage of the motor should be reduced during no load or light load conditions. This can be achieved by using an auto transformer equipped with control mechanisms for voltage adjustment. This is an expensive option that also requires much maintenance. An alternate method is to use a power electronic circuit designed to control the motor voltage. This option is often much cheaper and more efficient. In addition, system efficiency will be enhanced. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 121  Insulator Gate Bipolar Transistor (IGBT) Bipolar transistors are devices with relatively low losses in the power circuit (Collector circuit) during conduction period; due to their relatively low forward drop VCE when closed. Bipolar transistors are also more suitable for high switching frequencies than SCRs, bipolar transistors have very low current gains at the saturation region (when closed). Thus the base currents are relatively high, which makes the triggering circuits bulky, expensive and of low efficiency. On the other hand, MOSFETs are voltage – controlled devices that require very small input current. Consequently, the triggering circuit is much simpler and less expensive to build. In addition, the forward voltage drop VDS of a MOSFET is small for low voltage devices. At this voltage level, the MOSFET is a fast switching power device. Because of these features, MOSFETs replace bipolar transistors in low voltage applications (200 V) both the bipolar transistor and the MOSFET have desirable features and drawbacks. Combining these two in one circuit enhances the desirable and diminishes the drawbacks. The MOSFET is placed in the input circuit and the bipolar transistor in the output (Power circuit). These two devices can now be included on the same wafer; the new device is called the IGBT i.e., the IGBT has high input impedance as in MOSFET and low on state power loss as in BJT. 2. Gate Turn Off Thyristor (GTO) A GTO Thyristor is a pnpn device, which can be triggered on like an ordinary SCR by application of a small positive gate current pulse but has the capability of being turned off by a negative gate current pulse of proper amplitude. A GTO thus combines the merits of conventional thyristor and high voltage switching Thyristor. No forced commutation circuitry is required for GTOs. Hence, inverters using GTOs are compact and cheap. However, gate turn off current is high (typically ¼ to 1/5). Thus 4000 volts, 3000 A GTO may need 750 A gate current to turn it off. This facility permits construction of Inverter circuits without bulky and expensive forced commutation components used in ordinary Thyristor circuits. Further GTO has higher switching speed than the conventional Thyristor or power MOSFETs. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 122  Turn off action: When a negative bias is applied at the gate, excess carriers are drawn from the base region of the NPN transistor and collector current of the PNP transistor is diverted into the external gate circuit. Thus the base drive of NPN transistor is removed and this action removes the base drive of PNP transistor and finally stops the conduction. Protection of dv/dt and di/dt. To protect a power electronic device against excessive di/dt and dv/dt, a snubbing circuit must be used. The function of this circuit is to limit the current and voltage transients. The circuit is composed of a source voltage, a load and an SCR. The circuit has a snubbing inductance Ls to limit the di/dt in the current path. It also contains an RC circuit to limit the dv/dt across GTO. Power Converters: The power converters driving the traction motors consists of 1. Controlled rectifier (Line Converter) 2. DC Link 3. Inverter (Drive Converter) 4. Controllers (Micro processor) 1. Line Converter : It provides constant dc output required for inverter operation. It has GTO or IGBTs as switching devices, which can operate on all four quadrants. It controls phase angle of voltage and current and make current in phase with voltage so that unity power factor can be achieved. 2. DC Link : It is a link between Converter and Inverter. It comprise of L-C filter to smoothen ripples and a capacitor to provide constant input to inverter, in case of power failures (intermittent), panto bouncing, neutral section etc. It has got an over voltage protection (MUB), a resistance and a Thyristor connected across the DC link. 3. Inverter: It provides variable alternating voltage nd currents at desired frequency and phase for the control of AC Induction motors. There are two types of Inverter available viz., TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 123   Voltage source Inverters  Current source Inverters In traction duty, voltage source inverters are used. Because of low internal impedance, the terminal voltage of a voltage source Inverter remains substantially constant with variations in load. 4. Controllers : The controllers embody the control laws governing the load and motor characteristics and their interaction. To match the load and motor though the power controllers, the controller controls the input to the power controller. Description of Electrical Power Scheme (Schematic Circuit) Fig. 11.1 The overhead supply of 1500 V DC or 25 KV AC is connected to the traction system through a common single pantograph. The power supply collected by pantograph is fed to three equipments. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 124  a) Main Lightening arrestor which protects the entire power circuit from damages due to natural lightening affecting the OHE in the section. b) A fail safe High Voltage Detection Device (HVDD) detects the line voltage and regulates the HVCC and MVCC accordingly. c) The High Voltage change over switch (HVCC), which connects the pantograph either to 25 KV AC or 1500 V DC circuit of motor coach. When the OHE supply is AC, the HVCC take the position on AC side. On closing the vacuum circuit breaker (VCB), 25 KV AC is fed to main traction transformer which in turn will step down the voltage to 1473 volts and feed to medium voltage change over switch (MVCC). A separate surge arrestor ACSA is provided to arrest the surges at primary winding of main traction transformer. When the OHE supply is DC, the HVCC takes the position on DC side. On closing the DC Circuit Breaker, 1500 V DC is fed to Medium voltage change over switch (MVCC). A separate surge arrestor DCSA is provided between HVCC and DCCB to arrest surges developed while working on DC mode. L1 inductor, C1 capacitor and R1 resistor forms DC line filter to dampen various harmonics developed while working in DC mode. The MVCC also has two positions. When OHE supply is AC, MVCC connects the single phase 1473 volts AC supply to Line converter. When OHE supply is DC, MVCC connects the 1500 volts DC supply to Line converter. The Line Converter is common for both the OHE supplies which can be 25 KV AC or 1500 V DC supply. The line converter receives the input supply from medium voltage change over contactor which is either 1473 volts single phase AC supply received from secondary of traction transformer or 1500 V DC supply received from DCCB. The Line Converter coverts it to stabilized 2200 volts DC supply and feeds mainly to following three equipments: TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 125  a) 3-Phase Traction Inverter: The Traction Inverter inverts the 2200 volts DC Power to 3-phase Variable Voltage Variable Frequency and feeds 4 nos. of traction motors connected in parallel. Three phase Squirrel cage Induction Motors are used as traction motors. b) Diverting Chopper: The diverting chopper comes into function whenever the DC link voltage exceeds above preset voltage. The diverting chopper also helps in providing dynamic brakes when the train is in regenerative braking mode and the OHE turns non receptive. Such dynamic brakes are in function for a short duration till the change over takes from regenerative braking to electro pneumatic braking. c) Down Chopper: It converts the 2200 volts DC to 530 volts DC and feeds to following three equipments: i) 20 kVA dedicated inverter for Main Compressor Motor. 20 kVA Inverter converts 530 volts DC to 3-phase 415 volts AC. ii) 50 kVA Inverter 50 kVA Inverter inverts 530 volts DC to 3-phase 415 volts AC, and feeds auxiliary transformer. The Auxiliary Transformer has two secondary windings. a) One supplying 415 volts 3-phase AC to Auxiliary Machines b) Second supplying 220 Volts 3-phase AC to Lights and Fans in coaches. The load of lights and fans are on single phase of 140 volts evenly distributed across each phase and neutral. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 126  iii) 7 kW Battery Charger. 7 kW battery charger converts 530 volts DC to 110 volts DC for charging batteries and feeding control supply. Driving cab component description The main components in driving cab of AC DC BHEL EMU are as follows: Drivers control equipment The components mentioned in the following paragraph are available for the driver to control the train: Driver’s Panel Drivers Control Switch (DCS) The drivers control switch is used for switching the train on and enabling the functions of the master controller. Switch Panel (BL key panel) There are two rows of switches in switch panel. The first row consists of following switches: a) Shunting Switch b) Pantograph Up c) Pantograph Down d) Train Off e) Entering Neutral Section f) Fault Reset g) VCB / DCCB Trip h) VCB / DCCB Set TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 127  The second row consists of the following switches: a) Lamp Test b) Spare c) Spare d) Spare e) Spare f) Parking Brake ON / OFF g) Spare h) Spare Master controller cum Brake Controller The traction / brake controller is used for distributing the traction / braking torque request from the motorman to the train. This controller has 16 positions:  One (1) emergency brake position (EB)  Seven (7) brake positions (BP1, BP2, BP3, BP4, BP5, BP6, BP7)  One (1) coasting position (C)  Seven (7) traction positions (TP1, TP2, TP3, TP4, TP5, TP6, TP7) Dead-man switch The function „dead man‟ is incorporated in the traction / brake controller. To assure the driver is capable of driving the train an action form the driver is necessary to be able to power the train. To activate the dead-man the throttle handle must be turned for approximately 5 degrees when the mode selector is in forward or reverse position. Mode selector The mode selector is used for distributing the driving direction from the driver to the train. This mode selector has 3 positions:  Forward (F)  Neutral (N)  Reverse (R) TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 128 By moving this selector, a driving direction is chosen. This direction is only accepted by the drive control electronics when the train is not moving. Fault Indication Panel There are eight indications on Fault indication panel, they are as follows: a) General Fault b) E.P. Brake Fault c) Parking Brakes Applied d) C jumper Continuity e) OHE „ON‟ Indication f) Guard‟s supply „ON‟ Indication g) Master controller in Coasting Position h) Brakes Not Released Pneumatic Brake Controller It has 4 positions: 1. Release / Running position 2. Lap 3. Auto 4. Emergency The brake controller is used as a back up to brake the train. In normal operation all brake controllers in the train are in the running position. When a brake controller is not in the running position it is not possible to drive at a speed higher than 5 km/h. Driver’s Display Unit Configuration screen – Present date, time, vehicle status, vehicles present, EP status. F1 – Message presentation screen – Fault messages can be read. F2 – Start trip screen driver ID, Route ID, edit the data. F3 – End trip screed – continue or End – Enter – you will get trip details. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 129 F4 – Total screen – indicates line voltage, line current, speed, energy consumed / energy saved / mileage etc. F5 – Maintenance screen – Password is required to give reset. General Fault (Red) indication: When DCS is switched ON, it will illuminate and go after 10 sec., indicating that DCS is switched ON and LV supply is available. How to handle in case of faults:  Faults or malfunction of parts of the Traction and Auxiliaries will be indicated by the General Fault light.  The display will show the reason of the fault.  In case of a WARNING the fault light will be OFF after accepting the message.  In case of WARNING, there is no loss of performance. The maintenance staff should be informed to solve the problem after service.  In case of a MINOR FAULT performance can be less but traction power and Auxiliaries are still available.  In case of TRACTION FAULT traction power and ED brake will be lost on the motor coach with the fault.  In case of OFF traction, ED brake and Auxiliaries will be lost. Lights, fans for passengers and 110 volt control power will be fed from adjacent motor coach.  The driver can try to reset the fault via the button FAULT RESET (for at least 1 sec) only in case the fault has disappeared a reset will lead a reapplying of power. How to read Message in DDU Press F1, then i. If fault / warning message appear, then read it and press ENTER for next message(s). ii. If DDU shows that All messages accepted, then press CLR and read message and press ENTER for next message(s). How to give Fault Reset Important : Fault reset can be given from Fault Reset toggle switch in BL-box after inserting BL-key. Since at a time only one BL key can be inserted, so Fault Reset should be given from the motorman‟s DTC. i. In DTC D-Cab press Fault Reset toggle switch in BL box for 2 seconds. ii. In M / ch D-cab Ensure that all MCBs above Brake Controller are in ON position. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 130 Instructions for maintenance reset: CAUTION: i. Maintenance reset should not be given without advice of shed (PPIO). ii. Ensure that all MCBs above Brake Controller are in ON position. Steps for giving maintenance reset: i. Switch On DDU by switching ON display toggle switch in driver‟s desk. Observe status of motor coach; OK or OFF a) If coach is OK, maintenance reset is not required b) If coach is OFF, then proceed as follows –  At next stoppage of train bring panto down by rotating the Panto valve Kaba Key (Blue Key) anti-clockwise.  Press F5  Press 2000  Press 1 and keep it pressed for 15 seconds  Press ENTER ii. Wait for 30 seconds iii. Then read fault messages by pressing F1 iv. The ensuring that train is halted, raise the pantograph by rotating clockwise the Panto Valve Kaba Key. v. Read status of that vehicle (coach) OK or OFF. vi. Before leaving motor coach ensure that DDU is switched OFF. Component codes for AC – DC EMUs 2 13 k 6 First digit indicates the type of coach : 1 stands for DTC 2 stands for MC 3 stands for TC Second digit indicates function of the component : 11 – HVS – High Voltage System 12 – Static converter/battery Charger /Auxiliaries 13 – LVS – Low Voltage System 15 – TRC – Traction Control 16 - -VHC – Vehicle Control 21 – General Equipment and PLC 23 – Position Detection TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 131  34 – VIS – Vehicle Information System Third digit indicates component codes: A– Converter/Inverter Module B– Speed probe C– Capacitor D– Diode E– Heating element F– Safety device (Fuse/MCB/LA/Over load element) G– Battery H– Indication lamp K– Contactor/Relay L– Inductor M– Motor P– Panel meter Q– Circuit breaker R– Resistor S– Switch/Push button T– Transformer U– Transducer/Measuring device/Sensor V– Power Electronic device/Component W– Current Collector X– Connector Y– Magnet valve Z– Filter Circuit Fourth digit indicates Sr. No. of the item. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 132 Auxiliary machines : There are 18 aux. machines in AC/DC EMU. Sr. No. Description Qty. Motor No. Contactor 1 Inductor vessel fans 2 M1 & M2 213 K1 & K26 2 Bleeder motor 1 M15 213 K2 3 HT Room fans 2 M16& M17 213 K3 to K8 4 HEX cubicle fans 2 M16 & M7 213 K9 to K14 5 TFP radiator fans 4 M1 to M4 213 K15 & K16 6 TFP cooling pump 1 M5 213 K17 7 LCD cubicle fans 2 M11& M12 213 F10 & 213 F11 8 Aux. Inv. Cubicle fan 2 M13& M14 213 F12 & 213 F13 9 LCD oil pump 1 M9 5.5 kVA Inv.212 A1 10 Fan for cooling oil pump 1 M10 213 F9 Relays used in light & Fan circuits : 213 K18 - light & Fan selection to & from left side of motor coach 213 K19 - light & Fan selection to & from right side of motor coach 213 K 20 – Self motor coach supply 213 K30 – Power supply in motor coach OK 213 K 21 – Input supply (110V) from either side M / Ch 213 K 22 – Output supply (110V) to either side M / Ch 213 K 23 – 100% light ON 213 K 24 – 50% light ON 213 K 25 – Fans ON 213 K 33 213 K 34 – Lights OFF 213 K 35 – Fans OFF TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 133 Technical Data of Electrical equipments : 1. Traction Transformer: Continuous rating : 1312 kVA Turns ratio : 17:1 Primary voltage : 22.5 kV, 25 kV Sec. Voltage : 1326 V, 1473 V 2. Traction converter / inverter / aux. converter : 1. Line Converter : AC Mode DC Mode Input Voltage 1326 V AC 1500 V DC Input Current 900 Amps 900 Amps Output Voltage 2200 V DC 2200 V DC Output Current 525 Amps 525 Amps Power rating 1200 kW 1200 kW 2. Inverter: Input Voltage 2200 V DC Input Current 460 Amps Output Voltage 1950 V AC Power rating 1520 kVA 3. Aux. Down chopper: Input Voltage 2200 V DC Output Voltage 530 V DC Cooling Medium MIDEL Synthetic Ester TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 134 3. Traction Motor : Continuous 1 hour rating Power 295 kW 362 kW Voltage 1669 Volts 1669 Volts Current 136 Amps 163 Amps Speed 1259 rpm 1249 rpm Max. service speed 2750 rpm Gear ratio 16:69 Traction Faults for which reset can be given : Auto reset Maintenance reset Fault reset 12,13,14,15,16,17, 30,33,36,37,41 7,8,9,10,11,20,21,22, 18,19,28,42,45,46,51, 23,24,25,26,27,29,31, 52,53,55,56,57,58,59 32,38,39,44,47,48,49, 50,54,60,83,96,98 Reset to be given through laptop 86,87,88 & 89 – temperature sensors for traction motors 1,2,3 & 4 90,91,92 & 93 – speed sensors for traction motors 1,2,3 & 4 Message Details 10. Traction Fault - Inductor vessel fan 1 failing 11. Traction off - Both Inductor vessel fans failing 12. Traction off - Inductor temp. too high. 13. ED – Brake off - Inductor temp. high. 60. Traction fault - Inductor fan 2 not working 14. Traction and Aux. Off - TFP temp. too high. 15. Traction and Aux. Off - TFP failure. 17. ED-Brake off - TFP temp. high. 18. Warning - TFP oil level low. 19. Traction and Aux. off - TFP oil no circulation (No oil cooling) TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 135 21. Warning - HT Room fan high speed failing. 22. Warning - HT Room fans both speed failing. 23. Warning - HT Room fans low speed failing. 24. Warning - HT Room temp. too high. 25. Traction Off - HEX fans high speed failing. 26. Traction and Aux. Off - HEX fans both speed failing. 27. Warning - HEX fans low speed failing. 28. Traction and Aux. Off - HEX cubicle temp. too high. 39. Traction and Aux. Off - Pantograph control failing. 49. Traction and Aux. Off - Aux. on chopper failing. 50. Traction & Aux. Off - Internal Electronics problem. 51. Traction & Aux. Off - Control Air pressure too low. 52. Warning - LCD oil pump fan failing. 53. Warning - cooling fan – converter & Aux. Inv. Failing. 55. ED-Brake Fault - TM temp. high. 56. Traction fault - TM temp too high. 57. Traction fault - Traction/Conv. /Braking res. temp. high. 58. Traction fault - Traction Conv./Br. Res. temp. too high. 59. Traction & Aux. off - Traction converter temp. too high. 71. Warning - TFP temp. too high. 76. Warning - TFP temp. high. 77. Warning - OHE voltage too high. 83. Warning - No oil cooling transformer. 79. EP fault - EP brake pressure MC too low. 80. EP fault - EP brake pressure DTC/TC too low. 81. EP fault - EP brake pressure MC not released. 82. EP fault - EP brake pressure DTC/TC not released. 84. MR Pressure - Main compressor manually off. 85. No Traction - BP Pressure too low. TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 136  Frequently coming message Nos. 2,8,16,20,33,37,44,50,54,60,61,84 & 85 Type of Fault messages AR MR FR fault Warning 18 – low oil level in TFP 62 – TFP failing 71 – TFP temp. too high 76 – TFP temp. high 21- HT Room fans Hi-speed failing X 22 – HT Room fans both speeds fail X 23 – HT Room fan low speed failing X 24 – HT Room Temp. too high X 27 - HEX fans low speed failing X 52 - LCD pump fan failing X 53 - Cooling fan for converter & Aux. Inverter failing X 43 – PLC Battery low X 34 – Internal problem PLC prog. 40 – Line converter inhibited 63,64,67,68,69 & 72 – Internal Electronics problem MF 16 – Compressor OLR tripped X Minor 42 – Battery Charger failed X Failure 44 – Compressor Inverter failed X 45 – Position detection failed X EDF 13 – Inductor temp high X ED 17 – TFP temp. high X Brake 55 – Traction motor temp. high X Off Type of Fault messages AR MR FR fault TF 10 - Inductor fan 1 failing X Traction 60 - Inductor fan 2 failing X Off 11 – both inductor fans failing X 12 – inductor temp. too high X TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 137  25 – HEX. High speed failing X 48 – Traction fault X 56 – traction motor temp. too high X 57 – traction Converter/Breaking res. temp. high X 58 - traction Converter/Breaking res. temp. too high 85 – BP low 65,66 – Internal Electronics problem Off 9 – oil pump inverter failure X Traction 14 - TFP temp. too high X & Aux. 15 - TFP failure X Off 19 - No oil cooling TFP X 20 – 50 kVA Inv. failure X 26 - HEX both speed failed X 28 - HEX. cubicle temp. too high X 29 - AC line contactor failing X 32 – DCLC failing X 30 – DCCB failing X 41 – VCB failure X 31 – Line over current DC mode X 38 – Line over current AC mode X 33 – HVCC failed X 37 – MVCC failed X 36 – DCCB/VCB failed by MDC X 39 – Panto control failing X 49 – Aux. Dn. Chopper failing X 50 – Control Electronics problem X Type of Fault messages AR MR FR fault Off 51 – Control air pressure too low X Traction 54 – Traction fault X & Aux. 59 – Traction Converter temp. too high. X Off TRACTION ROLLING STOCK : THREE PHASE TECHNOLOGY Page 138