Flux switching machines (FSMs) that consist of all flux sources in the stator have been developed in recent years due to their advantages of single piece and robust rotor structure suitable for various speed applications. They can be categorized into three groups that are permanent magnet (PM) FSM, field excitation (FE) FSM, and hybrid excitation (HE) FSM. Both PMFSM and FEFSM has only PM and field excitation coil (FEC), respectively as their main flux sources, while HEFSM combines both PM and FECs. Among these FSMs, the FEFSM offers advantages of low cost, simple construction and variable flux control capabilities suitable for various performances. In this paper, design study and flux interaction analysis of a new 12S-10P and 12S-14P FEFSM with single direction of DC FEC winding are presented. Initially, design procedures of the FEFSM including parts drawing, materials and conditions setting, and properties setting are explained. Then, coil arrangement tests are examined to confirm the machine operating principle and position of each armature coil phase. Finally, flux interaction between DC FEC and armature coil, FEC flux capabilities at various current condition, induced voltage and initial torque are also analyzed.