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   IGBT  evaluated  
Insulated Gate Bipolar Transistors (IGBTs) are today's state-of-the-art power electronics for the traction system of electric (and diesel-electric) rail vehicles. They replace the previous inverter generation represented by GTO (gate turn-off thyristors).
Technology field: Optimisation of traction technologies
close main section General information
  close sub-section Description


Insulated Gate Bipolar Transistors (IGBTs) are today's state-of-the-art power electronics for the traction system of electric (and diesel-electric) rail vehicles. They replace the previous inverter generation represented by GTO (gate turn-off thyristors).

In contract to conventional transistors, IGBTs operate at very high currents (> 1000 A). The principle benefit of IGBTs over GTOs is a much (3 to 4 times) higher switching frequency. This reduces the current required and therefore the heat generated, giving smaller and lighter units. The high switching frequencies also smoothen the acceleration process and reduce the traction noise.

Fields of application

Power electronics based on IGBTs are used in a number of fields in industry and transportation.

close main section General criteria
  close sub-section Status of development: in use
    In the course of the last years, all major manufacturers of railway traction technologies have completely migrated to IGBT technology. This migration has already taken place some years ago in the MU segment and is presently taking place in the locomotive segment of around 7 MW.
  Time horizon for broad application: now
    (no details available)
  Expected technological development: highly dynamic

Although IGBTs have reached maturity, R&D dynamics is still high in this field, Major aims are:

  • raise blocking voltages
  • increase switching frequency
  • reduce losses
  • reduce weight

The IGBT itself is integrated in a complex power module which includes besides the transistor the circuits and the cooling etc. These "peripherals" offer even more potential for future optimisation than the IGBT itself.

    Energy efficiency
  Benefits (other than environmental): big
  • Reduced switching losses (compared to GTO)
  • Less cooling required (no organic coolants required)
  Barriers: low

Refurbishment costs

Refitting old vehicles with IGBTs is usually not profitable (for present energy prices). Diffusion is therefore essentially limited to stock renewal.

    Success factors:
    (no details available)
  Applicability for railway segments: high
    Type of traction:  electric - DC, electric - AC, diesel
    Type of transportation:  passenger - main lines, passenger - high speed, passenger - regional lines, passenger - suburban lines, freight
    IGBTs are generally applicable to electric traction motors. This includes electric and diesel-electric traction. Refitting old vehicles with IGBTs is expensive, but has been realised in some cases, e.g. NS Reizigers has refurbished their Sprinter train sets with IGBT choppers.
    Grade of diffusion into railway markets:
  Diffusion into relevant segment of fleet: 5 - 20%
  Share of newly purchased stock: > 50%

Diffusion into relevant segment of fleet

Most fleets have already a considerable share of vehicles with IGBTs, others like the SBB fleet don't have any IGBT stock yet.

Share of newly purchased stock

Siemens claims that virtually all electric rail vehicles presently produced at Siemens Transportation are based on IGBT traction systems.

  Market potential (railways): high
    (no details available)
    (no details available)
close main section Environmental criteria
  close sub-section Impacts on energy efficiency:
  Energy efficiency potential for single vehicle: 5 - 10%
  Energy efficiency potential throughout fleet: > 5%

Improved traction efficiency

According to an expert from Bombardier, the efficiency of the IGBT at payload is about 5 - 6% better than the efficiency of the GTO (95% vs. 90 % efficiency). The effect on energy efficiency in real operation maybe even bigger due to the fact that the relative advantage of IGBTs over GTOs is even higher at low loads. This may push the efficiency gain even beyond 10%. for instance, Japanese JR Hokkaido claims that IGBT controlled 3-phase AC motors save 15 % energy compared to their GTO predecessors.

Mass reduction

IGBT modules are generally lighter than GTO modules (some 30%). This may offer constructive advantages but is negligible for energy efficiency.

  Other environmental impacts: positive

Noise reduction

Japanese JR Hokkaido claims that IGBT controlled 3-phase AC motors reduce noise by 10% compared to their GTO counterpart.

close main section Economic criteria
  close sub-section Vehicle - fix costs: low
    IGBT drive technology is a mature technology in rail vehicles. It does not substantially increase the vehicle price compared GTO or other technology.
  Vehicle - running costs: significant reduction
    (no details available)
  Infrastructure - fix costs: none
    (no details available)
  Infrastructure - running costs: unchanged
    (no details available)
  Scale effects: low
    Scale effects within railways have already been exploited. Scale effects from mass markets are unlikely since the specifications (e.g. blocking voltage) for railway IGBTs require dedicated development and production.
  Amortisation: < 1 year
    (no details available)
close main section Application outside railway sector
  close sub-section Status of development outside railway sector: in use
    (no details available)
  Time horizon for broad application outside railway sector: now
    (no details available)
  Expected technological development outside railway sector: highly dynamic

cf.  XXX

At present, no innovations in power electronic replacing IGBTs are close to market stage in the low-power segment, which is usually an early monitor for later developments in the power segments relevant for railway applications.

  Market potential outside railway sector: high
    (no details available)
close main section Overall rating
  close sub-section Overall potential: very promising
  Time horizon: short-term
    The advent of IGBTs has yielded strong efficiency gains in electric drive technology. There are no barriers for introduction. However, diffusion is essentially limited to stock renewal since refurbishment is possible but usually too expensive.
References / Links:
Related projects:  Choppers for Sprinter train sets
Contact persons:
 date created: 2002-10-09
© UIC - International Union of Railways 2003
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