A Novel Self Cooling SRM for Electric Hand Tools

Electric hand tools require high efficiency, small-size, low cost, and improving convenience. To achieve these demands, Switched Reluctance Motor (SRM) is expected for electric hand tools motor as an alternative for blushless Permanent Magnet Synchronous Motor (PMSM). SRM is suited for electric hand tools from advantages such as the low manufacturing cost, the simple and robust structure, the high speed driving and operating under high temperature condition. However, SRM has a disadvantage that torque density is lower than it of PMSM. Therefore, SRM needs to add higher current than it of PMSM to achieve the same output torque. Moreover, winding temperature increases very fast by the large copper loss. To overcome this problem, this research proposes a self cooling SRM. Self cooling SRM can realize the same output torque and the same volume with the PMSM system including fan, and it can reduce the winding temperature by the self cooling effect.