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General information
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General criteria
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Status of development: prototype |
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- 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.
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Time horizon for broad application: 5 - 10 years |
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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. |
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Expected technological development: dynamic |
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(no details available) |
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Motivation:
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- LCC reduction
- Constructive advantages
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Benefits (other than environmental): big |
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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)
Source: Matsuoka, Kondoh, Hata 1997. |
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Barriers: medium |
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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. |
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Success factors:
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(no details available) |
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Applicability for railway segments: high |
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Type of traction: electric - DC, electric - AC
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Type of transportation: passenger - main lines, passenger - high speed, passenger - regional lines, passenger - suburban lines, freight
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In principle, wheel-mounted permanent magnet synchronous motors could be applied to all segments of electric fleet. |
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Grade of diffusion into railway markets:
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Diffusion into relevant segment of fleet: 0 % |
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Share of newly purchased stock: 0 % |
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Wheel-mounted permanent magnet synchronous motor is not marketable yet. |
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Market potential (railways): high |
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Barriers could impede introduction of wheel-mounted permanent magnet synchronous motors. Otherwise market potential could be very big in long-term perspective. |
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Example:
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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. |
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Environmental criteria
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Impacts on energy efficiency:
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Energy efficiency potential for single vehicle: 2 - 5% |
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Energy efficiency potential throughout fleet: 2 - 5% |
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A wheel-mounted permanent magnet synchronous motor has a higher efficiency
than the system consisting of asynchronous induction motor drive, mainly due to
missing transmission gears.
- Tests made on the RMT1A (an experimental motor developed at the Railway
Technical Research Institute (RTRI) in Tokyo) revealed, that efficiency is
improved from 87,9 % for a conventional asynchronous induction motor to 94,2 %
for the RMT1A wheel-mounted synchronous motor. This means a relative
improvement of 7 %.
- Koch et al. 2002 studying the feasibility of wheel-mounted permanent
magnet synchronous motor for a main-line locomotive assumed an efficiency of
conventional asynchronous motor gears of 93,6 % at payload and calculated
for the efficiency of the wheel-mounted synchronous machine a value of 95,6 %.
This is a relative improvement of only 2 %.
We heuristically assume that an intermediate value of 4 % is realistic for
many applications. This is used in the following elasticity table.
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Traction |
Brake energy
recovery |
Effect on efficiency of power
train |
Elasticity with regard to efficiency of power
train |
Effect on total energy consumption for
traction |
High speed
train |
electric |
no |
4 % |
1,00 |
4 % |
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yes |
1,11 |
4 % |
Intercity
train |
electric |
no |
1,00 |
4 % |
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yes |
1,12 |
4 % |
Regional
train |
electric |
no |
1,00 |
4 % |
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yes |
1,33 |
5 % |
Suburban
train |
electric |
no |
1,00 |
4 % |
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yes |
1,42 |
6 % |
Freight |
electric |
no |
1,00 |
4 % |
Range: |
4 - 6
% | |
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Other environmental impacts: positive |
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Noise
Noise is reduced compared to conventional drive solutions due to elimination
of gears and elimination of ventilation.
Lubricants
Through the elimination of gears the loss of lubricants into the environment
can be avoided. |
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Economic criteria
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Application outside railway sector (this technology is railway specific)
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Overall rating
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