With the successful completion of the trial pre-series Class 455 EMU with upgraded traction and auxiliary system supplied by Vossloh Kiepe, Porterbrook Leasing Company has contracted Vossloh Kiepe UK to upgrade the traction system in their fleet of 91 off Class 455 EMUs, Sub Classes 455/7, 455/8 and 455/9 with modern three-phase AC traction motors and Insulated-Gate Bipolar Transistor (IGBT) technology traction inverters. As part of a £40m investment in South West Trains’ Class 455 EMUs, the Class 455 EMUs are one of the first EMU fleets in the UK to benefit from this state of the art traction upgrade with the project being delivered from 2016.
This new technology transforms older units into modern trains and delivers an economical solution to the most pressing business needs including the increasing passenger demand. The cost for leasing and maintaining this fleet will be substantially lower than investing in new trains.
Vossloh Kiepe in Düsseldorf is responsible for the manufacture and delivery of the integrated solid state traction equipment whilst Vossloh Kiepe UK based in Birmingham provided the Turnkey Project responsibility for the design and integration engineering, approvals, installation and testing of the equipment.
The work started on the trial Class 455 Unit at Wimbledon depot in June 2014. On-track testing commenced in March 2015 and the Unit entered into service in April 2016. The second trial unit was also modified at Wimbledon depot and the production EMUs are being re-tractioned at Eastleigh depot with eight units completed to date.
The project includes the re-tractioning of the two motor bogies in each of the Class 455 Units Motor Second Open (MSO) vehicles where the current 2 off DC Motors per bogie are being replaced with 2 off new, lighter, axle-hung nose suspended three-phase AC traction motors per bogie that offer greater energy-saving efficiencies. The new AC traction motors have been designed to be direct replacements for the DC machines and the work also includes the replacement of the 750V DC camshaft control system on each EMU with an AC three phase Variable Voltage Variable Frequency (VVVF) inverter.
The weight saving with the new AC traction motors is typically 500 kg per motored axle less than the original design which will make the wheel sets more track friendly by their lower unsprung weight that assists with the improved performance of the re-tractioned train. There will also be reduced maintenance, service and repair costs as AC traction motors have a lower number of moving and wearing parts when compared with the original DC traction motors.
The new IGBT Traction System provides a regenerative braking facility that uses the traction motors as generators when the train is braking. The electrical energy generated is fed back into the 750 V third rail DC supply and offsets the electrical demands of other trains on the same network. Tests have shown that the energy consumption can be reduced by between 10 per cent and 30 per cent, depending on conditions. With the increasing cost of energy, regenerative braking will have a massive positive cost impact on the long-term viability of these trains. If the supply is non-receptive to the regenerated power, the generated power is dissipated by the rheostatic brake.
The project includes a replacement of the brake control equipment with a modern Knorr Bremse EP98 brake control system that will provide the necessary brake blending between this new electric or dynamic braking on the MSO and the existing conventional friction braking system on the four cars in the unit to maximise the savings that can be made. The Wheel Slide Protection (WSP) system is operable on all four vehicles of the unit and will also be upgraded to improve stopping distances and reduce the occurrences of wheel flats and other wheel tread faults in low adhesion conditions when compared to the existing system. The new braking system with WSP will have a major benefit with reducing friction brake and wheel set maintenance.
The key commercial and technical advantages compared with the original traction equipment may be summarised as follows:
- Improving reliability.
- Generating electricity into the traction power supply for use by other trains.
- Lower environmental impact with a lower carbon footprint.
- Reduced operating energy costs.
- Reduced use of the friction brake with lower brake pad and wheel disc wear.
- Reduced running costs by the lower unsprung mass reducing the amount of wear and tear on the rail infrastructure.
- Reduced maintenance with fa lower number of moving parts in the traction motors and supporting traction system.
- Reduced servicing costs by increasing mileage between major maintenance works from 10,000 miles to 15,000 miles thereby keeping trains in service for longer period.
- Advantages to freeing up depot space enabling the train operator to increase train capacity.
The scale of this contract has created new opportunities for installation personnel as well as engineers, designers and technicians that have joined Vossloh Kiepe’s project team. The modification of the rail vehicles has also generated valuable work for the railway maintenance facilities in Eastleigh.
This latest re-tractioning technology is highly attractive to a number of train operators and leasing companies. Porterbrook is currently looking at the possibility of undertaking similar re-tractioning work on other EMUs it owns and more recently Eversholt Rail Group has contracted with Vossloh Kiepe for a re-tractioning programme on 30 off its Class 321 25 kV electric multiple units following a pre-series traction upgrade on a similar unit. There are several fleets in the UK that could benefit from this technology, especially with the plans for further mainline electrification requiring new fleets and cascaded fleets of older refurbished EMUs.