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   Wheel-mounted permanent magnet synchronous motor  evaluated  
The wheel-mounted permanent magnet synchronous motor is an interesting alternative to conventional AC asynchronous motors with gear transmission. In a wheel-mounted construction the torque of the motor is directly transmitted to the wheel.
Technology field: Optimisation of traction technologies
open main section General information
close main section General criteria
  close sub-section Status of development: prototype
   
  • R&D in railways (DB, JR East and others) and railway manufacturers.
  • JR East is presently manufacturing test vehicles of Advances commuter train for Tokyo Metropolitan Area using wheel-mounted permanent magnet synchronous motors.
  • Engineers from Technical University Darmstadt have recently made a feasibility study (Koch et al. 2002) examining the potential of wheel-mounted permanent magnet synchronous motors for main line locomotives. The study showed no principal constructive barriers for such an option.
  Time horizon for broad application: 5 - 10 years
    Manufacturers claim that production could start quickly if there was a demand from railways. The power class of permanent magnet synchronous motors currently produced for busses is not too far away from the ones needed for light rail applications. Even so, broad application would take some years since refitting of existing vehicles is not an option.
  Expected technological development: dynamic
    (no details available)
    Motivation:
   
  • LCC reduction
  • Constructive advantages
  Benefits (other than environmental): big
   

Maintenance

Maintenance reduced (no gears and flexible couplings)

Constructive advantages

Small volume and direct drive facilitate low-floor and double-decked construction, independent wheel drives offer potential for gauge-adjustable vehicles.

Motor cooling

Due to lower losses, heat removal can be realised by an exterior water-cooling rather than ventilation. This reduces dirt contamination of motor and thus maintenance and wear.

Table 2: Features of wheel-mounted direct drive and its applications (Japanese perspective)

Direct Drive 3.gif

Source: Matsuoka, Kondoh, Hata 1997.
  Barriers: medium
   

Safety

Wheel-mounted permanent magnet synchronous motors may cause safety problems: If power failure occurs and the train has to be removed quickly to clear the track, the induced currents in the motor have to be handled (since induction effects cannot be switched off, due to permanent magnetism). The solution of this problem requires additional effort.

Complexity

Whereas 4 asynchronous motors can be fed by one inverter, permanent magnet synchronous motor need one individual inverter each.

Unsprung mass

In a wheel-mounted construction the heavy rotor magnets contribute to unsprung mass and put additional strain on wheel-track system.

Acceptance

Asynchronous motors are a successful standard technology. Consequently, reluctance to take the risk to introduce a new technology is high.
    Success factors:
    (no details available)
  Applicability for railway segments: high
    Type of traction:  electric - DC, electric - AC
    Type of transportation:  passenger - main lines, passenger - high speed, passenger - regional lines, passenger - suburban lines, freight
    In principle, wheel-mounted permanent magnet synchronous motors could be applied to all segments of electric fleet.
    Grade of diffusion into railway markets:
  Diffusion into relevant segment of fleet: 0 %
  Share of newly purchased stock: 0 %
    Wheel-mounted permanent magnet synchronous motor is not marketable yet.
  Market potential (railways): high
    Barriers could impede introduction of wheel-mounted permanent magnet synchronous motors. Otherwise market potential could be very big in long-term perspective.
    Example:
   

Tokyo commuter train

JR East is presently manufacturing test vehicles of Advances commuter train for Tokyo Metropolitan Area using wheel-mounted permanent magnet synchronous motors.
open main section Environmental criteria
open main section Economic criteria
no data available Application outside railway sector (this technology is railway specific)
open main section Overall rating
References / Links:  Koch 2000;  Matsuoka et al. 1997
Attachments:
Related projects:  High performance motor for direct drive
Contact persons:
 date created: 2002-10-09
 
 
© UIC - International Union of Railways 2003
 
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