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General information
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Description
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Most rail vehicles have several driven axles with separate power transmission. This includes both locomotives usually having a separate power train for each bogie and multiple units having several driven axles along the train. It is often feasible to shut off some of these driven bogies during partial load and operate the remaining ones at high load. Due to the fact that energy efficiency is usually lower for partial load than for maximum load, such a measure increases overall energy efficiency.
This measure requires a change of the on-board software only, since individual motor bogies always have a switch-off option for the case of failure. |
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General criteria
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Status of development: in use |
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Traction group switch-off is realised on the Re 465 locomotive of Swiss BLS
Lötschbergbahn.
Simulations have been made for the German ICE 3 EMU (Klose, Unger-Weber
2000). |
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Time horizon for broad application: 2 - 5 years |
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The measure could be realised on many trains by a software refit. However barriers could impede wide-spread application in the immediate future. |
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Expected technological development: dynamic |
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If empirical analysis confirms worries about negative long-term effects of idling on axle bearings, technological potential could lie in solving this problem. |
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Motivation:
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Energy efficiency |
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Benefits (other than environmental): none |
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(no details available) |
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Barriers: medium |
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Safety
If a traction group is switched off, its regenerative braking power does no
longer contribute to the total braking power available for rapid braking in case
of emergency. However, according to experts, the remaining braking power given
by the other traction groups and non-regenerative brakes (pneumatic, eddy
current) is sufficient for safety considerations. Nevertheless this issue may
give rise to some reservations about the traction group switch-off.
Adhesion
If a traction group is switched off, less force can be transmitted by the
wheels on the rail. The remaining adhesion is usually sufficient. However if the
train leaves the dry track of a tunnel and enters the wet track conditions
outside the tunnel, wheels could spin along. This problem however could be
solved by controlling adhesion and by switching the respective traction group
back on in time to keep wheels from spinning along.
Motor lifetime
For some locomotives (especially used in Switzerland), there are worries
about negative long-term effects of idling on rolling bearings of motor. These
conjectures which have neither been confirmed nor completely disproved could
represent a serious barrier on existing stock affected by this problem. For new
stock, it is likely that the issue could be solved by the development of
bearings fitted to this requirement. |
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Success factors:
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- Convincing concepts should be presented to eliminate the existing
acceptance problems.
- Conjectures of damage to rolling bearings of traction motors in some stock
could be settled by specific research efforts.
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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 in most electric locomotives and EMUs. Transmissibility is high since individual motor bogies always have a switch-off option for the case of failure. |
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Grade of diffusion into railway markets:
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Diffusion into relevant segment of fleet: < 5% |
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Share of newly purchased stock: 0 % |
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Only one known application: Swiss locomotive Re 465 on the BLS Lötschbergbahn. |
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Market potential (railways): not applicable |
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(no details available) |
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Example:
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Swiss locomotive Re 465 on the BLS Lötschbergbahn. |
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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: 1 - 2% |
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According to an expert, the saving potential is highly dependant on the efficiency profile of traction equipment and operation profile but will lie between 2 and 5% per vehicle.
The highest potential may be reached for traction equipment with strong load dependence in an operation profile with high time shares of partial load operation. |
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Other environmental impacts: neutral |
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(no details available) |
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Economic criteria
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Vehicle - fix costs: low |
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Refit measure: Personnel costs for realising software change.
New stock: additional purchasing costs very low or none. |
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Vehicle - running costs: significant reduction |
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(no details available) |
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Infrastructure - fix costs: none |
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(no details available) |
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Infrastructure - running costs: unchanged |
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(no details available) |
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Scale effects: medium |
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Since the measure consists in a software change, there are clear scale effects for each vehicle series running on the same software. |
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Amortisation: (no data) |
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Amortisation period will generally be short, but highly depends on the costs for the software measure and the number of stock of one series (running on the same software). |
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Application outside railway sector (this technology is railway specific)
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Overall rating
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Overall potential: very promising |
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Time horizon: mid-term |
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Traction group switch-off is a very promising measure for saving energy in electric traction. Since it only requires a software change, it could be realised in short-term perspective. However unconfirmed technological problems and lack of experience with this measure currently impede widespread introduction. The concept is promising enough to invest into R&D to rule out safety problems and eliminate technological barriers in mid-term perspective. |
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date created: 2002-10-09
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