This master thesis investigates the possibilities for performance improvements of synchronous machines with unidirectional application.The literature review part presents theories and applications of asymmetrical machine. Four categories regarding asymmetrical machine, namely mixed pole, saturation mitigation, pole shifting and asymmetrical pole shaping, are summarized. It is shown that asymmetrical concept offers characteristic improvement in one or both rotational directions. A field winding synchronous model was used in FEM simulation (FLUX 2D). Armature reaction effecton this machine is investigated. It is found that armature reaction has different effects with varying current angle.Two ideas regarding asymmetrical pole shaping are investigated. First of all, pole shoe cutting idea is investigated. It leads to increased airgap length and less output torque. Secondly, progressive airgap idea shows reduced armature reaction effect and improved power factor, but higher torque ripple.Furthermore, an improved idea is suggested to reduce the torque ripple. Performance improvement by assisted permanent magnet is also studied. Four ideas of this field are investigated. It is found that permanent magnet can be used to reduce saturation, improve power factor and output torque. The reasons for limited improvements are analyzed.