The railway transportation systems are important for the modern mass transport due to the fact that the railway vehicles have higher capacity and better energy efficiency compared with the road transportation vehicles. It is therefore important to ensure that the time schedule in the railway operation is kept. In bad weather conditions delays may appear due to the decreased adhesion at the wheel-rail contact. This reduces the acceleration and deceleration of the trains and may cause delays. Some modern passenger trains (e.g. ICE 3) are designed to overcome this problem with the help of a distributed traction. For that more axles of the train than the usual 4 axles for a locomotive are used for transmitting the tractive power, thus a lower tractive coefficient is required for each axle. This solution is not practical for the freight trains that are required to have a flexible composition of the train cars. The heavy-duty locomotives used for the freight trains are using therefore a higher tractive effort per axle and cannot use in wet weather condition all the installed power. Nowadays a second locomotive is used in order to increase the transmissible tractive power. A more economical solution is proposed in this work. The contact normal force, that is proportional with the maximum transmissible tractive effort, is increased with the use of an especially designed DC excited transversal flux linear actuator.This PhD thesis deals with the design optimization of an especially designed transversal flux DC excited linear actuator for railway applications. The actuator increases the normal force applied on the wheel-rail contact of the active axles of the locomotive. The maximum transmissible tractive effort, that is proportional to the normal force, is thus increased. The actuator can be used in the wet weather condition, when the adhesion coefficient of the wheel-rail contact is reduced by 35-45%. The actuator design is refined, starting from a previous existing configuration. The transversal flux design generates a big attractive force and a very low braking force. Optimization of the actuator magnetic core is done, using 2D and 3D Finite Element Method (FEM) models and analytical models for validation.