Replacement of auxiliary power supply system—A case study in an urban railway

This paper reports the results of a study into the economic replacement of the auxiliary power supply units that are installed in every two-car unit making up passenger trains. The core of the study is the determination of when the existing power supply units should be replaced by more technically advanced units. Conventional theory is used to determine the resulting internal rate of return for replacement at different points in time. The paper also discusses the many subjective factors involved and the assumptions that will need to be made in order to solve large replacement problems of this kind.