INDUCTIVE RAILWAY SWITCH POINT HEATING : Improved control algorithm and phase compensation analysis for an inductive turnout heating system, and comparison with a resistive heating system

Sammanfattning: Railway turnout heating is essential during the winter because snow and ice can hinder the movement of the switch. In Sweden, heating has traditionally been done using resistive heating wires mounted to the stock rail, but the technology is outdated and generally exhibits low efficiency and performance. Inductive heating systems such as Indheater, described in this exam work, has in previous studies shown great potential in reduction of the power consumption. Real world data comparing a resistive system and an Indheater system confirms this, with an energy consumption of the latter reaching 37,3 % of the resistive system’s consumption over two winter seasons. To achieve high efficiency and reliability, the heating system control algorithm is important, and during the work described in this report, fault detection was implemented to the programmable logic controller (PLC). Alarms will be triggered if the peak power is too low, which could indicate a heater malfunction. Additionally, detection of faulty switch position sensors and temperature sensors is also described. Given the dynamic nature of the Indheater system, calculations were performed to assess the electrical performance under both balanced and unbalanced load scenarios. Various sizes of phase compensating capacitors were compared. It is recommended to select a capacitor that provides a high power factor for a wide range of different loads, while still reducing the current enough at full load.