HVAC-Integrated Auxiliary Power Supply

SMA provides converters based on the MEE-NTSD platform of auxiliary powersupplies for the climate control of passenger compartment and driver's cab. Theconverters are integrated into the air conditioning units.

Two ET420 prototype DB AG commuter trains for greater Stuttgart, Germany, wererefurbished and tested in the DB AG's workshop in Krefeld, Germany, in 2005.

Compact and ultra-light-weight auxiliary powersupply

Electrically separating input converter

Available for various input voltages

Modular system for optimal adaptability to HVAC

Based on proven platform MEE-NTSD

High overload capacityallows trouble-free starting of motor loads

Compact and lightweightinput filters due to highlydynamic input currentcontrol

A multifaceted variety ofoptions allows project-specific adaptability

Integrated diagnosis system

Source: DB AG 2005

Figure 1: Refurbished ET420Plus EMU of the DB AG

Modernizing already-existing rail-way vehicles is always a challenge.The integration of significant electri-cal and mechanical upgrades notconsidered in the original designrequires clever and detailed solu-tions.

SMA's modular auxiliary powersupply, MEE-NTSD, is an innovativeplatform providing a solution for themost challenging tasks, as was themodernization of DB AG EMU's ofthe type ET 420, for example. In thesummer of 2005, two prototypeEMU's were refurbished in the DBKrefeld workshop. They belongedto the two last series delivered to theDB between 1989 and 1997. Inaddition to new seats or a publicaddress system, for example, an airconditioning system for the driver'scabs and the passenger compart-ment was retrofitted. In particular,the power supply for these upgradesystems proved to be a great chal-lenge. The existing onboard power

supply could not provide the extrapower needed for the additionalconsumers. An additional sourcehad to be installed in the air condi-tioning on the roof because theunderfloor space of the vehicle was

already full. As the roof of theET420 was not designed for addedloads, all new components had tobe as lightweight as possible.

The ET420 is electrically designedfor operation at 15 kV AC 16.7 Hz.The existing onboard power sup-plies as well as the drives are supplied via separated windings of a traction transformer. However,the winding provided for the exist-ing onboard supply was not suit-able, in terms of its power, for theadded load of the air conditioning.The traction winding, on the otherhand, has sufficient power re-serve. The additional power sup-ply for the air conditioning systemwas therefore designed to beconnected to the traction winding.This traction concept sees two

Auxiliary Power Supply for Air Conditioning Units

Concept for the Auxiliary Power Supply

Source: DB AG 2005

Figure 2: Refitted cooling system for passenger compartment

Source: DB AG 2005

for HVAC-Integrated Auxiliary Power Supply

Figure 3: Block circuit diagram of traction system with connection of the MEE-NTSD based auxiliary powersupply integrated into air conditioning units

Figure 4: 3-phase inverter module

windings per motorized car. Eachtraction winding is assigned a thyristor chopper as traction con-verter. The DC output of the trac-tion converters is connected inseries and supplies all tractionmotors simultaneously. This so-lution, of course, has substantialconsequences for the additionalpower supply. On the one hand, it must have an electric separationin order to avoid improper stress of the insulation of all consumerswithin the air conditioning unit. In order to minimize the trans-former load, on the other hand, acurrent which is as sinusoidal aspossible has to be drawn from the traction winding. The addi-tional auxiliary power supply mustbe able to cope with the voltagedistortion at the transformer causedby the thyristor traction converterand its emission of electromagneticinterferences.

MEE-NTSD as System Solution

ing input converter designed as asoft-switching power unit with activeinput current control and electricseparation by a medium-frequencytransformer. This input converterequipped with active input currentcontrol (PFC) guarantees a sinusoi-dal input current in phase with thedistorted input voltage. It provides aDC link where all fixed- and vari-able-frequency 3-phase inverters fordifferent loads within the air condi-tioning system are connected. DCoutputs can of course be realizedwith the MEE-NTSD auxiliary powersupply platform.

The MEE-NTSD power supply is opti-mized for the lowest system weight.The modules can be directly inte-grated into the air conditioningunits. Each air conditioning unit istherefore equipped with its ownpower supply.

In addition to its mechanical modu-larity, the MEE-NTSD-based auxilia-

Due to these very high requirementsSMA's MEE-NTSD was selected asthe auxiliary power supply system.It consists of an electrically separat-

for HVAC-Integrated Auxiliary Power Supply

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Input voltages e. g. 1 x 370 V AC from traction transformer or optionally 600 / 750 V DC from catenary or 3rd railavailable with and without electric separation

AC output 1 e.g. fixed-frequency 3 x 400 V AC, 50 HzAC output 2 (option) e.g. variable-frequency up to 3 x 560 V AC, 70 Hz

other AC outputs are possibleDC output (option) e.g. 24 V DC, other voltages are possibleDimensions as required by the vehicle

Technical DataTechnical data of MEE-NTSD for HVAC-integrated converters (example)

ry power supply is also electricallyvery flexible. It can be used at ACas well as DC input voltages.Systems without electric separationand even the direct connection to a

catenary or 3rd rail with a nominalvoltage of 600 or 750 V DC arepossible. The active input currentcontrol is used in order to complywith the requirements for high input

impedances even without heavyinput chokes. Improper influence ofthe existing infrastructure by thenew systems is thus avoided.

Conclusion

SMA's modular MEE-NTSD auxilia-ry power supply is a sophisticated,modular and very lightweight plat-form which provides significantadvantages for the modernizationof railway vehicles, even those de-signed 40 years ago. It can be flexi-bly and cost-effectively used for agreat variety of projects.

Figure 5: MEE-NTSD auxiliary power supply for integration into air conditioning unit

SMA Railway Technology GmbH

Miramstrasse 8734123 KasselGermanyTel. +49 561 50634-6000Fax +49 561 50634-6001E-Mail: Info@SMA-Railway.com www.SMA-Railway.com