In variable speed applications, machines with variable field flux such as wound field synchronous machines (WFSMs), inherently have advantages in loss saving compared to fixed field flux drives such as permanent magnet (PM) machines in field-weakening region. However, the WFSM normally lacks the ability to produce as much reluctance torque as the PM machine due to its negligible saliency. This paper introduces a low cost flux barrier structure in the rotor design to improve the saliency and thus the torque production of a conventional synchronous machine. Effects of the WFSM parameters on torque and output power capability are first investigated using the dq equivalent circuit model. Observations are: (1) it is beneficial to have a larger saliency design to improve maximum torque capability and save copper losses, (2) the choice of d-axis synchronous reactance needs to be carefully made to achieve decent corner speed and corner torque at the same time, (3) good torque (power) speed capability can be achieved with a large saliency design. Results are then verified with finite element (FE) calculations. A comparison is made with a conventional salient pole structure whereby it is shown that total loss is reduced in the field-weakening region and efficiency is improved as a result, making this machine a serious candidate for traction applications.