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Z_LIM DEMO: Zero Wheel Slip Linear Induction Motor

Z_LIM DEMO: Zero Wheel Slip Linear Induction Motor


2017 to 2018

Project staff

Dr Roberto Palacin


Rail Safety and Standards Board (RSSB)


We have proved the feasibility of reducing dependence on the friction between wheel and rail for traction and braking forces. The approach needs minimal or no changes to existing infrastructure.

The Z_LIM (Zero Wheel Slip Linear Induction Motor) concept maximises the potential impact. It opens up the possibility of retrofitting as well as new rolling stock applications. Linear motor technology has the ability to increase tractive and braking effort beyond conventional rolling stock. This will lead to an increase in railway system capacity. The increase in capacity has to be balanced against the extra cost and energy usage of the linear motor equipment.

Phase 1: assessing feasibility

We now know that linear motor technology provides a feasible way of increasing braking performance and capacity. Further development of the control strategies could bring similar or greater capacity gains with lower energy input. Increases in rail heating would also be relatively small.

Phase 2: developing a device

We are developing a credible, capable and cost-effective Z_LIM device. This will fulfil the expected performance outlined during the feasibility study. It will improve braking capability and capacity gains.

Dr Roberto Palacin led the project. It was sponsored by the UK’s Rail Safety and Standards Board (RSSB) as part of the Predictable and Optimised Braking Competition.