In April this year, our Ljubljana workshop completed a major overhaul of Siemens Desiro EMUs owned by the passenger operator SŽ-Potniški promet. The works, which took two and a half years to complete, started on 13 September 2016 when the first unit entered Ljubljana Center’s shop, and involved a total of 30 major revisions – 10 on two-car units and 20 on three-car units.
Compared to mid-life overhauls, a major overhaul comprises more repair work on the converters of the auxiliary equipment, traction power converters, the underframe, the brakes, interior equipment, and – what is easy to notice – application of an anti-graffiti coating over the entire body, which improves the general image of the trains and is significantly faster and more environmentally friendly than redoing the whole paintwork. Additionally to the overhaul works, degraded parts of traction motor insulation were renewed, loose window panes were replaced, and a prototype retractable thread board was retrofitted onto one of the EMUs for testing.
The thread board is mounted under the train’s sliding door and automatically slides in position when the door open to ensure that passengers are able to enter and exit a train with safety at stations with excessively large platform gaps. To achieve optimal functionality, the concept is based on applicable standards, with appropriate components selected as to facilitate the production and installation onto the train. The boards were manufactured and tested at Divača Center. Before installation, a vehicle modification blueprint had to be prepared, which included mechanical processing, welding, assembly, and testing.
In the winter from late 2017 through early 2018, a solution was finally found to the issue concerning snow-related breakdown of high-voltage insulation in traction motor windings. Characterized by fine snow crystals, which pass right through the filters, this type of ‘cold’ snow caused several cases of stator windings’ insulation breakdown in the past, with more than half of traction motors knocked out in some winters. To counter the issue, custom-made covers with filters were installed on a total of ten motors. The measure turned out to be effective, as no charges were reported in the winter of early 2019. Moisture-resistant filters were installed first, but had to be changed too frequently, so the testing was cancelled and then resumed in summer once new filters were installed. Currently two types of filters are in use, one for summer and one for winter season. A total of 34 traction motors, or 28% are currently fitted with said covers, which is high enough a number of testing units to be able to assess the filters’ effectiveness come winter. It is expected that the entire EMU fleet will be fitted with the covers. The covers are a SŽ-VIT design, and were produced entirely at our workshops.
A project is currently on-going to install WiFi and GSM-R on the EMUs.
