A fast calculation method of transient hot spot temperature for the design of dry‐type on‐board transformers

Abstract

The design of the dry-type on-board traction transformer (OBTT), a new lightweight method in the traction system of electric multiple units, needs to consider the transient hot spot temperature (HST) under different railroad line operating conditions. In order to quickly calculate the transient HST of dry-type OBTT when operating under different railroad line conditions, a calculation method (hereinafter referred to as GP-HST method) by combining an enhanced genetic programming algorithm (GP) with computational fluid dynamics (CFD) is presented. First, intercept a section from the railroad line to be calculated and use the CFD method to calculate the transient HST of the section railroad line. Then, the enhanced GP modelling is driven by this section of railroad line measured and simulated data. Next, a calculation model with an implicit mathematical correlation between railroad line operating conditions and the dry-type OBTT transient HST is established. Finally, the calculation model quickly calculates the transient HST of the remaining railroad line in operation. To validate the presented method, the calculation model obtained using the presented method is used to calculate the transient HST for another railroad line with significantly different operating conditions, and it is compared with the direct use of the CFD method. The calculation results show that the GP-HST method reduces the simulation time of the CFD method from 950 to 0.25 min with a maximum error, mean absolute error, and mean relative error of 1.856 K, 0.778 K, and 0.22%, respectively, for a railroad line with a running time of about half an hour. This shows that the GP-HST method can effectively help to improve the design efficiency of dry-type OBTT. K E Y W O R D Scalculation model, genetic programing (GP), hot-spot temperature (HST), on-board traction transformer (OBTT) | INTRODUCTIONElectric multiple units (EMU) are the high-speed train of electric power supply. The heart of its power supply systemthe on-board traction transformer (OBTT), is responsible for stepping down the voltage of 25 kV in the supply network to the rated operating voltage of the equipment. In addition, OBTT is the heaviest single piece of equipment in the power supply system, accounting for about 12%-18% of the mass of vehicle weight [1][2][3]. Currently, all OBTTs in EMUs are of the oil-cooled type. The insulating oil required for a single oilimmersed OBTT alone is about 1.5 tons, about 30% of the total mass of OBTT. The excessive mass of the OBTT will not only limit train operating speed but also increase the operating energy consumption. Dry-type OBTT is currently the primary lightweight method of OBTT, which changes the traditional oilThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.