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High power IGBT traction drives

Marc DEBRUYNE/Master Expert Traction Systems

Summary

The ALSTOM main high power IGBT traction drives using PALIX water cooled powermodules are described, namely the AEM7 refurbished locomotives for Amtrak US, the Dieselelectric locomotives for Syria, Sri Lanka and Iran Railways and the series of 500 FreightEurope electric locomotives for SNCF, which are part of our range of PRIMA locomotives.

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1. IntroductionWhen the first 3,3kV-1200A IGBT transistors appeared on the market in 1997, nobody couldimagine the place this component would take in high power traction drives. Today evidence isthat the GTO thyristor is no more the semiconductor switch that equips the electric tractiondrives at the very beginning of the 21st century, the IGBT transistor takes over everywhere.All the market segments from the electric bus to the most powerful locomotives definitelychose the IGBT converters.

The research and development program initiated by ALSTOM in early 1997 with the help ofseveral laboratories and institutes has enabled us to master the use of high voltage IGBTs.Innovative solutions had to come up to face the specificity of high power traction drives forthe railway applications. Since this time ALSTOM has got many references in high powerIGBT traction drives, namely the AEM7 refurbished locomotives for Amtrak US, the Dieselelectric locomotives for Syria, Sri Lanka and Iran and the series of 500 Freight Europeelectric locomotives for SNCF.

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2. ONIX range and the high power traction drivesUsually we are used to defining the traction drive converters by the nominal power they areable to control and their input voltage.

From 1995 up to now ALSTOM Transport has been developing a comprehensive range ofIGBT converters for the traction applications: the ONIX range. ONIX extends from350V-100kW up to 3kV- 1500kW.

The buses or trolley buses are fitted with compact water cooled ONIX 350 converters,metros and trams are equipped with air cooled ONIX 800 rated at 400/600kW, EMUs withair or water cooled ONIX 1500 or 3000 of 800/1000kW.

At the upper right part of the voltage-power plan the 4 axle locomotives are generallypowered with 4 independent drives of 1000/1500kW each. We consider that this voltage-power zone corresponds to the high power traction which will be described hereafter.

500

1000

2000

4000

100 200 500 1000 1500

Onix 350

Converter Power (kW)

Co

nve

rter

Vo

ltag

e (V

)

BusBus TrolleyTrolley TramTram MetroMetro EMUEMU HSTHST LocoLoco

ONIX 800

ONIX 1500

ONIX 3000

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3. Functionality for high power IGBT traction drives

There are no fundamental differences between a converter intended for metros or tramscompared with that one for a locomotive.

However the higher voltage of the DC bus and the larger electric energy stored within thecapacitors connected to the DC bus have to be considered carefully. As this energy increasessignificantly potential dysfunction must be properly managed, mainly in case ofsemiconductor short circuits.As usual a safe IGBT-diode commutation must be ensured to guarantee a good reliability, thecomponents must stay inside the safe operating current-voltage area defined by themanufacturer at any time, for any temperature. This can be done by a very low strayinductance within the switching loop that has not to exceed about 100nH and by anappropriate IGBT gate control. Due to the higher power and voltage the converter dimensionsare generally enlarged compared with those of low power, low voltage converters which donot facilitate the IGBT commutation as the stray inductances are directly linked to thevolumes.

For this reason the topology of IGBT modules and the input capacitors have to be carefullydesigned so as to minimize this stray inductance. Multi terminal capacitors with an internalinductance as low as 50nH, specially designed for these applications have to be used, theconnection of the capacitors to the IGBT modules is made by copper laminated bus barswhich represent a very small inductance. If necessary small decoupling capacitorsimplemented very close to the IGBTs modules also contribute to suppress a part of thecommutation over-voltage. The technology of the bus bar is a sensitive point as voltage andcurrent go up. The partial discharges and the internal temperature have to be kept low to avoidan aging of the insulation material. Today their maximum surface temperature is limited to105°C, which imposes the use of thick copper layers which entail some mechanicalconstraints. Studies are in progress to improve the technology so as to increase the operatingtemperature.

Assure a safe switching

Power electronics

Input capacitorsInput capacitors

Laminated bus barsLaminated bus bars

Decoupling Decoupling capacitorscapacitors

Gate drives

didi//dt dt controlcontrol

Vce Vce clampingclamping

Protect the traction drive

IGBT monitoringIGBT monitoring

Short circuit detectionShort circuit detection

Functionality Sub-assemblySolution

Vge Vge clampingclamping

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The gate drive is always a key element in the commutation process. For high power tractiondrives several functions aim at better controlling the on and off switching in any circumstancehave been implemented, as di/dt control and/or collector-emitter voltage clamping.

In the high power traction drive applications particular care must be brought to fight againstDC bus capacitor short circuits in case of an IGBT failure as the current may reach very highvalues. For this reason the collector emitter voltage is permanently monitored and comparedto the input signal coming from the controller, in case of IGBT desaturation or an abnormalstate, a special firing-blocking sequence strategy is initiated to minimize the consequences ofthe failure, the idea being to switch off quickly the converter semiconductors to avoid a shoot-through. All types of converter short-circuits have to be mastered to end the sequences safely.If it is rather easy to cut off a IGBT when is fired on a already established short-circuit (nosaturation), it is more difficult to control it when the short-circuit occurs during the on state ofthe IGBT (desaturation), for that the gate-emitter voltage must be carefully controlled intransient mode and kept below a certain value by a clamping device.

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4. Semiconductor evolution and IGBT transistors

The first samples of IGBT for traction applications appeared in the early 1990’s. At that timethey allowed us to build converters for 600 and 750V DC lines with 1600V then 1700Vdevices respectively. The high power converters started with the introduction in 1997 of the3300V packs allows the direct operation with 1500V DC lines or regulated DC buses of1800V up to 2000V. The 4,5kV IGBT which followed is mainly used in press-pack version toreplace the 4,5kV GTO thyristors in refurbishment applications where the DC bus is rated upto 2,8kV as it was usual in most of the high power drives equipped with GTOs. The 4,5kVmodule version with only a 6kv insulation between its baseplate and ground requires anisolated heatsink that can be a drawback for traction use where the cooling system is generallyat earth. The 6,5kV IGBT insulated at 10kV promises an easy direct access to 3kV DC linesthanks to a simplification of the power schemes, 3,3kV devices in series are no longernecessary. This device is due to be delivered in series next year.For the high power applications two IGBT packages have to be considered:• the well known modules which provide the insulation to the ground as thosecommonly used for the urban and suburban vehicles,• the press-packs similar of those used for GTOs.

19851985 19901990 19951995 20002000 20052005

1,7kV-2x800A1,7kV-2x800A

3,3kV- 1200A3,3kV- 1200A

GTOGTO 4,5kV-4000A4,5kV-4000A

4,5kV-1200A4,5kV-1200A

6,5kV-600A6,5kV-600A

1,6kV-1200A1,6kV-1200A

IGBTIGBT

Some high power IGBTs

FUJIFUJIPPIPPI

1200A-4,5kV1200A-4,5kV

TOSHIBATOSHIBAPPIPPI

1200A-4,5kV1200A-4,5kV

EUPECEUPECModuleModule

1200A-3,3kV1200A-3,3kV

EUPECEUPECModuleModule

600A-6,5kV600A-6,5kV

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The IGBT press-pack can be a suitable solution for very high voltage applications wheneverseveral devices have to be connected in series. As with this kind of package technology afailure always finishes by a short circuit not an opened circuit, in some cases presenting veryhigh thermal cycling constraints the press-packs may present an advantage as they use pressedchips less sensitive to temperature variations

In the on going traction applications the power schemes do not use any more devices in seriesdue to the high voltage withstand capability, furthermore thanks to extensive study programs(European RAPSDRA project) carried out by institutes and IGBT manufacturers the IGBTmodule was made much more robust against thermo-mechanical constraints, the replacementof copper by AlSiC in the IGBT baseplate goes in this direction.

At the end we are considering that the module package profiting of a large return ofexperience in the urban domain remains with the current technology the best compromise interms of cost, simplicity of use, reliability requirements. The products presented hereafter areexclusively built with IGBT modules.

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5. PALIX™ Range: power modules for high power applications

The development of high power, high voltage IGBT traction drives widely took advantage ofthe large return of experience acquired in the urban and suburban applications and entailednoticeable advancements in numerous fields of power electronics.

A new and comprehensive power module range, PALIX™, was created to answer anytraction power from 3 to 6MW, a new cooling system based on glycoled water plates enabledto benefit the optimal performances from IGBTs while keeping a good thermal marginassuring the high reliability level. Low stray inductance copper laminated bus bars allowinghigh current flows had to be used to ensure a safe IGBT commutation, the passivecomponents, mainly the capacitors, progressed drastically making possible a compact lay-outgreatly appreciated in the railway high power traction drives as the space is always tight.

The PALIX™ water cooled IGBT modules have been developed with a high level ofstandardization to ensure an important carry over between all the multi-voltage electriclocomotives of the PRIMA™ class and with the Diesel electric locomotives applications too.

The PALIX™ modules can cover all the needs of the power schemes of the PRIMA™ range.5 of them are 6kV insulated; the last one benefits a 10kv insulation level for the 3kV lineapplications.

Water cooled power modules Water cooled power modules for the PRIMA locomotive rangefor the PRIMA locomotive range

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6. High power IGBT traction drive applications

It is difficult to be exhaustive, the following part quickly presents some key applications ofhigh power modules for traction systems, namely the AEM7 locomotives, first series of 6MWelectric locomotives equipped with IGBTs, the Diesel electric locomotives for Syria and thelarge series of Freight locomotives for SNCF

6.1 AEM7 locomotives for AMTRAKAmtrak, the American railway company, which run in the North East Corridor (NEC)between Boston New York and Washington decided some years ago to refurbish a part of itsAEM7 passenger locomotive fleet. These locomotives originally had been fitted with DCmotor traction drives based on oil cooled thyristor controlled rectifiers.

They have been in commercial service since 1981.

AEM7 locomotive refurbishmentFirst IGBT series locomotive in the world

•ASEA traction drives•Service in 1981•DC motors•Thyristor rectifiers•Oil cooling•Fleet: 53 locomotives

•ALSTOM traction drives•Service in Feb 2000•AC motors•ONIX IGBT inverters•Water cooling•Fleet: 30 locomotives

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Attempts to equip these powerful locomotives, about 6000kW, with GTO based AC drivesfailed due to a lack of volume left in the body. At the end an IGBT traction drive based onPALIX modules was envisaged and its compactness ensured the project feasibility but itwas a real challenge to enter the electric equipment within such a narrow place due to theshort length of the body.

The AEM7 locomotives operate with three different supplies: 12,5kV and 25kV at 60Hz and12kV at 25Hz. Each asynchronous traction motor delivers a traction power of 1250kW at 125mph (200km/h). The electric braking is generally regenerative with a maximum power of4300kW, limited to 2200kW in rheostatic mode.The auxiliary power for the whole trainset is rated at 1375 KVA to ensure at any time a highlevel of comfort to the passengers.The auxiliary function always has priority over the traction, in case of failure of the auxiliaryconverter the traction inverter N°2 is diverted to ensure the feeding of the three phase 480V-60Hz network.The input rectifiers are interlaced to reduce the line current distortion at a minimum

� Customer: AMTRAK (US)� Order: 30 locomotives� Service: Feb 2000

Boston-Washington� Type: AEM7� Contract: Refurbishment with

IGBT AC drives� Supply: 25 kV-60Hz

12,5kV-60Hz12 kV-25Hz

� Power: ~ 6000kW input5000kW traction4326kW regeneration2290kW rheostatic1375kVA auxiliaries

� Effort: 230kN @ 70kmh� Max speed: 125mph (~ 200kmh)� Bogie: BoBo

� Power scheme: 4 AC traction drives4 PMCFs intercaled4 motor inverters1 auxiliary inverter4 rheo choppers

� Semiconductors: IGBT 3,3kV-1200A� Converter cooling: Glycoled water� Power modules: c NIX 1500-PALIX� Control: AGATE Control� Motor: 1250 kW

15780 Nm at starting1985rpm @125mph

� Transformer: 7326 KVA4 x 1050VTap changer13,2 T

� Mass: 91T

ASM1

ASM2

ASM3

ASM4

480V-60Hz1375KVA

12,5 & 25kV-60Hz12kV - 25Hz

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while the power factor is maintained to unity. The four intermediate 2kV buses are linkedtogether via the 2f (here 2*25Hz) filter inductances to equally share the power between the 4input rectifiers.

The first locomotive was delivered in late 1999 and commercial service started in February2000.At this time fifteen passenger trainsets are daily running between the cities of Boston, NewYork and Washington.

6.2 Diesel Electric Locomotives for Syria

This Diesel electric locomotive for Syria Railways is the first one of a large series of heavyfreight locomotives fitted with IGBT AC/AC traction drives.

The same mechanical lay-out with identical products have been used for the 10 units for Sri-Lanka and for the 100 units for Iran Railways ensuring a optimum reference proven carryover.

AEM7 Amtrak LocomotiveTraction Central Block

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The traction system is based on two independent traction drives. Each one via 3

PALIX modules controls 3 asynchronous motors in parallel. Another PALIX phase leg isdedicated to the rheostatic chopper function in braking mode. The DC bus voltage varies from900 to 1800V depending on the required traction power.

Since March 2000 an increasing fleet of more than 20 AD32C Diesel electric CoColocomotives haul daily 1800T heavy loads in Syria and ten similar ones have been in servicesince September 2000 in Sri-Lanka. The first locomotive for Iran is due to be delivered inearly 2002.

MainAlternator

Diesel Engine

Rectifier

ASM

ASM

ASMINVERTER 1

Rheo Chopper

ASM

ASM

ASM

INVERTER 2

Rheo Chopper

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6.3 Prima Range

The dual voltage locomotive BB427000 is part of a large SNCF order of 500 Europe freightlocomotives to be delivered from 2001 until 2008.All these locomotives are part on the new PRIMA range of ALSTOM locomotives whichcan address the European market with its multi-voltage locomotives based on PALIX IGBTtraction drives.

For this family a high level of standardization is reached in any field to ensure a carry over ashigh as possible between all traction drives whatever the line voltage involved.

S d (k /h)

Effort (kN)

0

50

100

150

200

250

300

350

400

450

500

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Rheostatic or regenerative braking

Starting effort: 320kNMax speed: 140km/hTractive power: 4200kWBraking power: 2600kWWeight :90t

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The different power schemes of the PRIMA locomotive range were studied as early as1997/1998 as a whole with the goal to reuse a maximum of parts and sub-assemblies.All the PRIMA schemes can be covered with only 4 PALIX modules fitted with proven3,3kV-1200A IGBTs whatever the voltage line. For example, with 3kV line an innovativescheme named “PMCFs series” was developed. The aim was to keep the DC intermediate busat 1800V with its negative pole always linked to ground, this procedure avoids an over-insulation and allows the reuse of a large part of components sized for 1500V line, namelyDC bus capacitors, PALIX inverters,

traction motors and auxiliary converters. Only the upper PALIX module used, as an inputrectifier, has to be 10kV insulated for 3kV lines.

Each motor block houses two independent axles drives plus a cooling tower located at theright side. There are two motor blocks located against the lateral walls in the locomotivebody.

DJ(C)

DJ(M)

}X 3=

~380 V~

M1

CVS-AUX

PMCF 3kV

PMCF & RH Inverter

25 kV-50Hz25 kV-50Hz15 kV- 16Hz 2/315 kV- 16Hz 2/3

3000 V DC3000 V DC1500 V DC1500 V DC

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The two axle compartments and theirs components are strictly identical except the length ofthe water pipes which have to be connected to their respective air-water radiators both locatedwithin the cooling tower.

Recently, in May 2001, the first BB427000 dual voltage locomotives successfully passed theSNCF validation and homologation tests allowing them to run on the RFF infrastructuretracks. By the end of this year seventeen locomotives will be delivered, ten of them will start afreight commercial service in December 2001.

BB427000: motor block for 2 axles

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7 Conclusion

The number of high power IGBT traction drives is increasing daily. At this time about 70locomotives with 700 PALIX™ modules operate but the total number of orders alreadyexceeds 760 units as shown in the reference chart. This represents a fleet of 7000 PALIX™power modules up to 2008.

The 3,3kV-1200A IGBT is now a standard produced by several manufacturers. Its extensiveuse in industrial and traction applications for high power converters makes it cost effective. Inthe very near future the 6,5kV IGBTs will be available for mass production for 3kVapplications, compared with the 3,3kV devices. Its use will probably be smaller due to thelimited market addressed but it will allow us to jump a new step by a drastic simplification ofthe power schemes.

DEL/ELDEL/EL TypeType CustomerCustomer PowerPower SupplySupply SpeedSpeed QuantityQuantity DeliveryDelivery

Loc AD32C Syria Railways 2370kW Diesel 120km/h 30 1999

Loc AEM7 Amtrak 6000kW 12,5 & 25kV-60Hz12kV-25Hz 200km/h 30 1999

Loc AD27C Sri Lanka 1900kW Diesel 110km/h 10 2000

Loc AD43C Iran Railways 2877kW Diesel 140km/h 100 2001

Motor car

Fossil fuel Bombardier 3700kW Turbine 240km/h 1 2000

Loc 427000 SNCF 4200kW 25kV-50Hz1500V 140km/h 415 2001/2008

25kV-50Hz1500 & 3000VLoc 437500 SNCF 4200kW 140kmh 31 2003/2008

Loc NJTNew Jersey

Transit2600kW Diesel 160km/h 33 2003

Loc 437000 SNCF 4200kW 140km/h 54 2002/200825kV-50Hz

15kV-16,7Hz1500V

Loc Egypt Railways 700kW Diesel 80km/h 30 2003